diff --git a/go.mod b/go.mod
index 632206d..3fd611a 100644
--- a/go.mod
+++ b/go.mod
@@ -7,8 +7,10 @@
 	github.com/cenkalti/backoff/v3 v3.1.1
 	github.com/gogo/protobuf v1.3.1
 	github.com/golang/protobuf v1.3.2
+	github.com/grpc-ecosystem/go-grpc-middleware v1.0.1-0.20190118093823-f849b5445de4
 	github.com/opencord/voltha-lib-go/v3 v3.2.3
 	github.com/opencord/voltha-protos/v3 v3.4.1
+	github.com/opentracing/opentracing-go v1.1.0
 	go.etcd.io/etcd v0.0.0-20190930204107-236ac2a90522
 	google.golang.org/grpc v1.25.1
 )
diff --git a/internal/pkg/core/device_handler.go b/internal/pkg/core/device_handler.go
index 4452b8f..f735e27 100644
--- a/internal/pkg/core/device_handler.go
+++ b/internal/pkg/core/device_handler.go
@@ -32,6 +32,8 @@
 	"github.com/cenkalti/backoff/v3"
 	"github.com/gogo/protobuf/proto"
 	"github.com/golang/protobuf/ptypes"
+	grpc_middleware "github.com/grpc-ecosystem/go-grpc-middleware"
+	grpc_opentracing "github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing"
 	"github.com/opencord/voltha-lib-go/v3/pkg/adapters/adapterif"
 	"github.com/opencord/voltha-lib-go/v3/pkg/flows"
 	"github.com/opencord/voltha-lib-go/v3/pkg/log"
@@ -43,6 +45,7 @@
 	of "github.com/opencord/voltha-protos/v3/go/openflow_13"
 	oop "github.com/opencord/voltha-protos/v3/go/openolt"
 	"github.com/opencord/voltha-protos/v3/go/voltha"
+	"github.com/opentracing/opentracing-go"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
@@ -643,7 +646,18 @@
 // doStateInit dial the grpc before going to init state
 func (dh *DeviceHandler) doStateInit(ctx context.Context) error {
 	var err error
-	if dh.clientCon, err = grpc.Dial(dh.device.GetHostAndPort(), grpc.WithInsecure(), grpc.WithBlock()); err != nil {
+	// Use Intercepters to automatically inject and publish Open Tracing Spans by this GRPC client
+	dh.clientCon, err = grpc.Dial(dh.device.GetHostAndPort(),
+		grpc.WithInsecure(),
+		grpc.WithBlock(),
+		grpc.WithStreamInterceptor(grpc_middleware.ChainStreamClient(
+			grpc_opentracing.StreamClientInterceptor(grpc_opentracing.WithTracer(opentracing.GlobalTracer())),
+		)),
+		grpc.WithUnaryInterceptor(grpc_middleware.ChainUnaryClient(
+			grpc_opentracing.UnaryClientInterceptor(grpc_opentracing.WithTracer(opentracing.GlobalTracer())),
+		)))
+
+	if err != nil {
 		return olterrors.NewErrCommunication("dial-failure", log.Fields{
 			"device-id":     dh.device.Id,
 			"host-and-port": dh.device.GetHostAndPort()}, err)
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.gitignore b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.gitignore
new file mode 100644
index 0000000..c198e6a
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.gitignore
@@ -0,0 +1,202 @@
+# Created by .ignore support plugin (hsz.mobi)
+### Go template
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+*.test
+*.prof
+### Windows template
+# Windows image file caches
+Thumbs.db
+ehthumbs.db
+
+# Folder config file
+Desktop.ini
+
+# Recycle Bin used on file shares
+$RECYCLE.BIN/
+
+# Windows Installer files
+*.cab
+*.msi
+*.msm
+*.msp
+
+# Windows shortcuts
+*.lnk
+### Kate template
+# Swap Files #
+.*.kate-swp
+.swp.*
+### SublimeText template
+# cache files for sublime text
+*.tmlanguage.cache
+*.tmPreferences.cache
+*.stTheme.cache
+
+# workspace files are user-specific
+*.sublime-workspace
+
+# project files should be checked into the repository, unless a significant
+# proportion of contributors will probably not be using SublimeText
+# *.sublime-project
+
+# sftp configuration file
+sftp-config.json
+### Linux template
+*~
+
+# temporary files which can be created if a process still has a handle open of a deleted file
+.fuse_hidden*
+
+# KDE directory preferences
+.directory
+
+# Linux trash folder which might appear on any partition or disk
+.Trash-*
+### JetBrains template
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio and Webstorm
+# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
+
+# User-specific stuff:
+.idea
+.idea/tasks.xml
+.idea/dictionaries
+.idea/vcs.xml
+.idea/jsLibraryMappings.xml
+
+# Sensitive or high-churn files:
+.idea/dataSources.ids
+.idea/dataSources.xml
+.idea/dataSources.local.xml
+.idea/sqlDataSources.xml
+.idea/dynamic.xml
+.idea/uiDesigner.xml
+
+# Gradle:
+.idea/gradle.xml
+.idea/libraries
+
+# Mongo Explorer plugin:
+.idea/mongoSettings.xml
+
+## File-based project format:
+*.iws
+
+## Plugin-specific files:
+
+# IntelliJ
+/out/
+
+# mpeltonen/sbt-idea plugin
+.idea_modules/
+
+# JIRA plugin
+atlassian-ide-plugin.xml
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+fabric.properties
+### Xcode template
+# Xcode
+#
+# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore
+
+## Build generated
+build/
+DerivedData/
+
+## Various settings
+*.pbxuser
+!default.pbxuser
+*.mode1v3
+!default.mode1v3
+*.mode2v3
+!default.mode2v3
+*.perspectivev3
+!default.perspectivev3
+xcuserdata/
+
+## Other
+*.moved-aside
+*.xccheckout
+*.xcscmblueprint
+### Eclipse template
+
+.metadata
+bin/
+tmp/
+*.tmp
+*.bak
+*.swp
+*~.nib
+local.properties
+.settings/
+.loadpath
+.recommenders
+
+# Eclipse Core
+.project
+
+# External tool builders
+.externalToolBuilders/
+
+# Locally stored "Eclipse launch configurations"
+*.launch
+
+# PyDev specific (Python IDE for Eclipse)
+*.pydevproject
+
+# CDT-specific (C/C++ Development Tooling)
+.cproject
+
+# JDT-specific (Eclipse Java Development Tools)
+.classpath
+
+# Java annotation processor (APT)
+.factorypath
+
+# PDT-specific (PHP Development Tools)
+.buildpath
+
+# sbteclipse plugin
+.target
+
+# Tern plugin
+.tern-project
+
+# TeXlipse plugin
+.texlipse
+
+# STS (Spring Tool Suite)
+.springBeans
+
+# Code Recommenders
+.recommenders/
+
+
+coverage.txt
+
+#vendor
+vendor/
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.travis.yml b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.travis.yml
new file mode 100644
index 0000000..702fa5b
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/.travis.yml
@@ -0,0 +1,21 @@
+sudo: false
+language: go
+go:
+  - 1.8.x
+env:
+  - DEP_VERSION="0.3.2"
+
+before_install:
+  # Download the binary to bin folder in $GOPATH
+  - curl -L -s https://github.com/golang/dep/releases/download/v${DEP_VERSION}/dep-linux-amd64 -o $GOPATH/bin/dep
+  # Make the binary executable
+  - chmod +x $GOPATH/bin/dep
+
+install:
+  - dep ensure
+
+script:
+ - make test
+ 
+after_success:
+  - bash <(curl -s https://codecov.io/bash)
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/CHANGELOG.md b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/CHANGELOG.md
new file mode 100644
index 0000000..0e64822
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/CHANGELOG.md
@@ -0,0 +1,30 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
+
+Types of changes:
+- `Added` for new features.
+- `Changed` for changes in existing functionality.
+- `Deprecated` for soon-to-be removed features.
+- `Removed` for now removed features.
+- `Fixed` for any bug fixes.
+- `Security` in case of vulnerabilities.
+
+## [Unreleased]
+### Added
+- This CHANGELOG file to keep track of changes.
+
+## 1.0.0 - 2018-05-08
+### Added
+- grpc_auth 
+- grpc_ctxtags
+- grpc_zap
+- grpc_logrus
+- grpc_opentracing
+- grpc_retry
+- grpc_validator
+- grpc_recovery
+
+[Unreleased]: https://github.com/grpc-ecosystem/go-grpc-middleware/compare/v1.0.0...HEAD 
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/CONTRIBUTING.md b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/CONTRIBUTING.md
new file mode 100644
index 0000000..dd52ab8
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/CONTRIBUTING.md
@@ -0,0 +1,20 @@
+# Contributing
+
+We would love to have people submit pull requests and help make `grpc-ecosystem/go-grpc-middleware` even better 👍.
+
+Fork, then clone the repo:
+
+```bash
+git clone git@github.com:your-username/go-grpc-middleware.git
+```    
+
+Before checking in please run the following:
+
+```bash
+make all
+```
+
+This will `vet`, `fmt`, regenerate documentation and run all tests.
+
+
+Push to your fork and open a pull request.
\ No newline at end of file
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/Gopkg.lock b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/Gopkg.lock
new file mode 100644
index 0000000..ebdcb75
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/Gopkg.lock
@@ -0,0 +1,123 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "cloud.google.com/go"
+  packages = ["compute/metadata"]
+  revision = "2d3a6656c17a60b0815b7e06ab0be04eacb6e613"
+  version = "v0.16.0"
+
+[[projects]]
+  name = "github.com/davecgh/go-spew"
+  packages = ["spew"]
+  revision = "346938d642f2ec3594ed81d874461961cd0faa76"
+  version = "v1.1.0"
+
+[[projects]]
+  name = "github.com/gogo/protobuf"
+  packages = ["gogoproto","proto","protoc-gen-gogo/descriptor"]
+  revision = "342cbe0a04158f6dcb03ca0079991a51a4248c02"
+  version = "v0.5"
+
+[[projects]]
+  branch = "master"
+  name = "github.com/golang/protobuf"
+  packages = ["jsonpb","proto","ptypes","ptypes/any","ptypes/duration","ptypes/struct","ptypes/timestamp"]
+  revision = "1e59b77b52bf8e4b449a57e6f79f21226d571845"
+
+[[projects]]
+  name = "github.com/opentracing/opentracing-go"
+  packages = [".","ext","log","mocktracer"]
+  revision = "1949ddbfd147afd4d964a9f00b24eb291e0e7c38"
+  version = "v1.0.2"
+
+[[projects]]
+  name = "github.com/pmezard/go-difflib"
+  packages = ["difflib"]
+  revision = "792786c7400a136282c1664665ae0a8db921c6c2"
+  version = "v1.0.0"
+
+[[projects]]
+  name = "github.com/sirupsen/logrus"
+  packages = ["."]
+  revision = "f006c2ac4710855cf0f916dd6b77acf6b048dc6e"
+  version = "v1.0.3"
+
+[[projects]]
+  name = "github.com/stretchr/testify"
+  packages = ["assert","require","suite"]
+  revision = "69483b4bd14f5845b5a1e55bca19e954e827f1d0"
+  version = "v1.1.4"
+
+[[projects]]
+  name = "go.uber.org/atomic"
+  packages = ["."]
+  revision = "8474b86a5a6f79c443ce4b2992817ff32cf208b8"
+  version = "v1.3.1"
+
+[[projects]]
+  name = "go.uber.org/multierr"
+  packages = ["."]
+  revision = "3c4937480c32f4c13a875a1829af76c98ca3d40a"
+  version = "v1.1.0"
+
+[[projects]]
+  name = "go.uber.org/zap"
+  packages = [".","buffer","internal/bufferpool","internal/color","internal/exit","zapcore"]
+  revision = "35aad584952c3e7020db7b839f6b102de6271f89"
+  version = "v1.7.1"
+
+[[projects]]
+  branch = "master"
+  name = "golang.org/x/crypto"
+  packages = ["ssh/terminal"]
+  revision = "94eea52f7b742c7cbe0b03b22f0c4c8631ece122"
+
+[[projects]]
+  branch = "master"
+  name = "golang.org/x/net"
+  packages = ["context","context/ctxhttp","http2","http2/hpack","idna","internal/timeseries","lex/httplex","trace"]
+  revision = "a8b9294777976932365dabb6640cf1468d95c70f"
+
+[[projects]]
+  branch = "master"
+  name = "golang.org/x/oauth2"
+  packages = [".","google","internal","jws","jwt"]
+  revision = "f95fa95eaa936d9d87489b15d1d18b97c1ba9c28"
+
+[[projects]]
+  branch = "master"
+  name = "golang.org/x/sys"
+  packages = ["unix","windows"]
+  revision = "13fcbd661c8ececa8807a29b48407d674b1d8ed8"
+
+[[projects]]
+  branch = "master"
+  name = "golang.org/x/text"
+  packages = ["collate","collate/build","internal/colltab","internal/gen","internal/tag","internal/triegen","internal/ucd","language","secure/bidirule","transform","unicode/bidi","unicode/cldr","unicode/norm","unicode/rangetable"]
+  revision = "75cc3cad82b5f47d3fb229ddda8c5167da14f294"
+
+[[projects]]
+  name = "google.golang.org/appengine"
+  packages = [".","internal","internal/app_identity","internal/base","internal/datastore","internal/log","internal/modules","internal/remote_api","internal/urlfetch","urlfetch"]
+  revision = "150dc57a1b433e64154302bdc40b6bb8aefa313a"
+  version = "v1.0.0"
+
+[[projects]]
+  branch = "master"
+  name = "google.golang.org/genproto"
+  packages = ["googleapis/rpc/status"]
+  revision = "7f0da29060c682909f650ad8ed4e515bd74fa12a"
+
+[[projects]]
+  name = "google.golang.org/grpc"
+  packages = [".","balancer","balancer/roundrobin","codes","connectivity","credentials","credentials/oauth","encoding","grpclb/grpc_lb_v1/messages","grpclog","internal","keepalive","metadata","naming","peer","resolver","resolver/dns","resolver/passthrough","stats","status","tap","transport"]
+  revision = "5a9f7b402fe85096d2e1d0383435ee1876e863d0"
+  version = "v1.8.0"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  inputs-digest = "b24c6670412eb0bc44ed1db77fecc52333f8725f3e3272bdc568f5683a63031f"
+  solver-name = "gps-cdcl"
+  solver-version = 1
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/Gopkg.toml b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/Gopkg.toml
new file mode 100644
index 0000000..0a7d4c1
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/Gopkg.toml
@@ -0,0 +1,35 @@
+[[constraint]]
+  name = "github.com/gogo/protobuf"
+  version = "0.5.0"
+
+[[constraint]]
+  branch = "master"
+  name = "github.com/golang/protobuf"
+
+[[constraint]]
+  name = "github.com/opentracing/opentracing-go"
+  version = "1.0.2"
+
+[[constraint]]
+  name = "github.com/sirupsen/logrus"
+  version = "1.0.3"
+
+[[constraint]]
+  name = "github.com/stretchr/testify"
+  version = "1.1.4"
+
+[[constraint]]
+  name = "go.uber.org/zap"
+  version = "1.7.1"
+
+[[constraint]]
+  branch = "master"
+  name = "golang.org/x/net"
+
+[[constraint]]
+  branch = "master"
+  name = "golang.org/x/oauth2"
+
+[[constraint]]
+  name = "google.golang.org/grpc"
+  version = "1.8.0"
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/LICENSE b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/LICENSE
new file mode 100644
index 0000000..b2b0650
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/LICENSE
@@ -0,0 +1,201 @@
+                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
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+          of the NOTICE file are for informational purposes only and
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+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
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+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
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+
+   7. Disclaimer of Warranty. Unless required by applicable law or
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+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
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+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright [yyyy] [name of copyright owner]
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
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\ No newline at end of file
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/README.md b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/README.md
new file mode 100644
index 0000000..224069b
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/README.md
@@ -0,0 +1,84 @@
+# Go gRPC Middleware
+
+[![Travis Build](https://travis-ci.org/grpc-ecosystem/go-grpc-middleware.svg?branch=master)](https://travis-ci.org/grpc-ecosystem/go-grpc-middleware)
+[![Go Report Card](https://goreportcard.com/badge/github.com/grpc-ecosystem/go-grpc-middleware)](https://goreportcard.com/report/github.com/grpc-ecosystem/go-grpc-middleware)
+[![GoDoc](http://img.shields.io/badge/GoDoc-Reference-blue.svg)](https://godoc.org/github.com/grpc-ecosystem/go-grpc-middleware)
+[![SourceGraph](https://sourcegraph.com/github.com/grpc-ecosystem/go-grpc-middleware/-/badge.svg)](https://sourcegraph.com/github.com/grpc-ecosystem/go-grpc-middleware/?badge)
+[![codecov](https://codecov.io/gh/grpc-ecosystem/go-grpc-middleware/branch/master/graph/badge.svg)](https://codecov.io/gh/grpc-ecosystem/go-grpc-middleware)
+[![Apache 2.0 License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](LICENSE)
+[![quality: production](https://img.shields.io/badge/quality-production-orange.svg)](#status)
+[![Slack](slack.png)](https://join.slack.com/t/improbable-eng/shared_invite/enQtMzQ1ODcyMzQ5MjM4LWY5ZWZmNGM2ODc5MmViNmQ3ZTA3ZTY3NzQwOTBlMTkzZmIxZTIxODk0OWU3YjZhNWVlNDU3MDlkZGViZjhkMjc)
+
+[gRPC Go](https://github.com/grpc/grpc-go) Middleware: interceptors, helpers, utilities.
+
+## Middleware
+
+[gRPC Go](https://github.com/grpc/grpc-go) recently acquired support for
+Interceptors, i.e. [middleware](https://medium.com/@matryer/writing-middleware-in-golang-and-how-go-makes-it-so-much-fun-4375c1246e81#.gv7tdlghs) 
+that is executed either on the gRPC Server before the request is passed onto the user's application logic, or on the gRPC client either around the user call. It is a perfect way to implement
+common patterns: auth, logging, message, validation, retries or monitoring.
+
+These are generic building blocks that make it easy to build multiple microservices easily.
+The purpose of this repository is to act as a go-to point for such reusable functionality. It contains
+some of them itself, but also will link to useful external repos.
+
+`grpc_middleware` itself provides support for chaining interceptors, here's an example:
+
+```go
+import "github.com/grpc-ecosystem/go-grpc-middleware"
+
+myServer := grpc.NewServer(
+    grpc.StreamInterceptor(grpc_middleware.ChainStreamServer(
+        grpc_ctxtags.StreamServerInterceptor(),
+        grpc_opentracing.StreamServerInterceptor(),
+        grpc_prometheus.StreamServerInterceptor,
+        grpc_zap.StreamServerInterceptor(zapLogger),
+        grpc_auth.StreamServerInterceptor(myAuthFunction),
+        grpc_recovery.StreamServerInterceptor(),
+    )),
+    grpc.UnaryInterceptor(grpc_middleware.ChainUnaryServer(
+        grpc_ctxtags.UnaryServerInterceptor(),
+        grpc_opentracing.UnaryServerInterceptor(),
+        grpc_prometheus.UnaryServerInterceptor,
+        grpc_zap.UnaryServerInterceptor(zapLogger),
+        grpc_auth.UnaryServerInterceptor(myAuthFunction),
+        grpc_recovery.UnaryServerInterceptor(),
+    )),
+)
+```
+
+## Interceptors
+
+*Please send a PR to add new interceptors or middleware to this list*
+
+#### Auth
+   * [`grpc_auth`](auth) - a customizable (via `AuthFunc`) piece of auth middleware 
+
+#### Logging
+   * [`grpc_ctxtags`](tags/) - a library that adds a `Tag` map to context, with data populated from request body
+   * [`grpc_zap`](logging/zap/) - integration of [zap](https://github.com/uber-go/zap) logging library into gRPC handlers.
+   * [`grpc_logrus`](logging/logrus/) - integration of [logrus](https://github.com/sirupsen/logrus) logging library into gRPC handlers.
+
+
+#### Monitoring
+   * [`grpc_prometheus`⚡](https://github.com/grpc-ecosystem/go-grpc-prometheus) - Prometheus client-side and server-side monitoring middleware
+   * [`otgrpc`⚡](https://github.com/grpc-ecosystem/grpc-opentracing/tree/master/go/otgrpc) - [OpenTracing](http://opentracing.io/) client-side and server-side interceptors
+   * [`grpc_opentracing`](tracing/opentracing) - [OpenTracing](http://opentracing.io/) client-side and server-side interceptors with support for streaming and handler-returned tags
+
+#### Client
+   * [`grpc_retry`](retry/) - a generic gRPC response code retry mechanism, client-side middleware
+
+#### Server
+   * [`grpc_validator`](validator/) - codegen inbound message validation from `.proto` options
+   * [`grpc_recovery`](recovery/) - turn panics into gRPC errors
+
+
+## Status
+
+This code has been running in *production* since May 2016 as the basis of the gRPC micro services stack at [Improbable](https://improbable.io).
+
+Additional tooling will be added, and contributions are welcome.
+
+## License
+
+`go-grpc-middleware` is released under the Apache 2.0 license. See the [LICENSE](LICENSE) file for details.
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go
new file mode 100644
index 0000000..45a2f5f
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go
@@ -0,0 +1,183 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+// gRPC Server Interceptor chaining middleware.
+
+package grpc_middleware
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+)
+
+// ChainUnaryServer creates a single interceptor out of a chain of many interceptors.
+//
+// Execution is done in left-to-right order, including passing of context.
+// For example ChainUnaryServer(one, two, three) will execute one before two before three, and three
+// will see context changes of one and two.
+func ChainUnaryServer(interceptors ...grpc.UnaryServerInterceptor) grpc.UnaryServerInterceptor {
+	n := len(interceptors)
+
+	if n > 1 {
+		lastI := n - 1
+		return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+			var (
+				chainHandler grpc.UnaryHandler
+				curI         int
+			)
+
+			chainHandler = func(currentCtx context.Context, currentReq interface{}) (interface{}, error) {
+				if curI == lastI {
+					return handler(currentCtx, currentReq)
+				}
+				curI++
+				resp, err := interceptors[curI](currentCtx, currentReq, info, chainHandler)
+				curI--
+				return resp, err
+			}
+
+			return interceptors[0](ctx, req, info, chainHandler)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	return func(ctx context.Context, req interface{}, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+		return handler(ctx, req)
+	}
+}
+
+// ChainStreamServer creates a single interceptor out of a chain of many interceptors.
+//
+// Execution is done in left-to-right order, including passing of context.
+// For example ChainUnaryServer(one, two, three) will execute one before two before three.
+// If you want to pass context between interceptors, use WrapServerStream.
+func ChainStreamServer(interceptors ...grpc.StreamServerInterceptor) grpc.StreamServerInterceptor {
+	n := len(interceptors)
+
+	if n > 1 {
+		lastI := n - 1
+		return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+			var (
+				chainHandler grpc.StreamHandler
+				curI         int
+			)
+
+			chainHandler = func(currentSrv interface{}, currentStream grpc.ServerStream) error {
+				if curI == lastI {
+					return handler(currentSrv, currentStream)
+				}
+				curI++
+				err := interceptors[curI](currentSrv, currentStream, info, chainHandler)
+				curI--
+				return err
+			}
+
+			return interceptors[0](srv, stream, info, chainHandler)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	return func(srv interface{}, stream grpc.ServerStream, _ *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+		return handler(srv, stream)
+	}
+}
+
+// ChainUnaryClient creates a single interceptor out of a chain of many interceptors.
+//
+// Execution is done in left-to-right order, including passing of context.
+// For example ChainUnaryClient(one, two, three) will execute one before two before three.
+func ChainUnaryClient(interceptors ...grpc.UnaryClientInterceptor) grpc.UnaryClientInterceptor {
+	n := len(interceptors)
+
+	if n > 1 {
+		lastI := n - 1
+		return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+			var (
+				chainHandler grpc.UnaryInvoker
+				curI         int
+			)
+
+			chainHandler = func(currentCtx context.Context, currentMethod string, currentReq, currentRepl interface{}, currentConn *grpc.ClientConn, currentOpts ...grpc.CallOption) error {
+				if curI == lastI {
+					return invoker(currentCtx, currentMethod, currentReq, currentRepl, currentConn, currentOpts...)
+				}
+				curI++
+				err := interceptors[curI](currentCtx, currentMethod, currentReq, currentRepl, currentConn, chainHandler, currentOpts...)
+				curI--
+				return err
+			}
+
+			return interceptors[0](ctx, method, req, reply, cc, chainHandler, opts...)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+		return invoker(ctx, method, req, reply, cc, opts...)
+	}
+}
+
+// ChainStreamClient creates a single interceptor out of a chain of many interceptors.
+//
+// Execution is done in left-to-right order, including passing of context.
+// For example ChainStreamClient(one, two, three) will execute one before two before three.
+func ChainStreamClient(interceptors ...grpc.StreamClientInterceptor) grpc.StreamClientInterceptor {
+	n := len(interceptors)
+
+	if n > 1 {
+		lastI := n - 1
+		return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+			var (
+				chainHandler grpc.Streamer
+				curI         int
+			)
+
+			chainHandler = func(currentCtx context.Context, currentDesc *grpc.StreamDesc, currentConn *grpc.ClientConn, currentMethod string, currentOpts ...grpc.CallOption) (grpc.ClientStream, error) {
+				if curI == lastI {
+					return streamer(currentCtx, currentDesc, currentConn, currentMethod, currentOpts...)
+				}
+				curI++
+				stream, err := interceptors[curI](currentCtx, currentDesc, currentConn, currentMethod, chainHandler, currentOpts...)
+				curI--
+				return stream, err
+			}
+
+			return interceptors[0](ctx, desc, cc, method, chainHandler, opts...)
+		}
+	}
+
+	if n == 1 {
+		return interceptors[0]
+	}
+
+	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
+	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+		return streamer(ctx, desc, cc, method, opts...)
+	}
+}
+
+// Chain creates a single interceptor out of a chain of many interceptors.
+//
+// WithUnaryServerChain is a grpc.Server config option that accepts multiple unary interceptors.
+// Basically syntactic sugar.
+func WithUnaryServerChain(interceptors ...grpc.UnaryServerInterceptor) grpc.ServerOption {
+	return grpc.UnaryInterceptor(ChainUnaryServer(interceptors...))
+}
+
+// WithStreamServerChain is a grpc.Server config option that accepts multiple stream interceptors.
+// Basically syntactic sugar.
+func WithStreamServerChain(interceptors ...grpc.StreamServerInterceptor) grpc.ServerOption {
+	return grpc.StreamInterceptor(ChainStreamServer(interceptors...))
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/doc.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/doc.go
new file mode 100644
index 0000000..7168950
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/doc.go
@@ -0,0 +1,69 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+/*
+`grpc_middleware` is a collection of gRPC middleware packages: interceptors, helpers and tools.
+
+Middleware
+
+gRPC is a fantastic RPC middleware, which sees a lot of adoption in the Golang world. However, the
+upstream gRPC codebase is relatively bare bones.
+
+This package, and most of its child packages provides commonly needed middleware for gRPC:
+client-side interceptors for retires, server-side interceptors for input validation and auth,
+functions for chaining said interceptors, metadata convenience methods and more.
+
+Chaining
+
+By default, gRPC doesn't allow one to have more than one interceptor either on the client nor on
+the server side. `grpc_middleware` provides convenient chaining methods
+
+Simple way of turning a multiple interceptors into a single interceptor. Here's an example for
+server chaining:
+
+	myServer := grpc.NewServer(
+	    grpc.StreamInterceptor(grpc_middleware.ChainStreamServer(loggingStream, monitoringStream, authStream)),
+	    grpc.UnaryInterceptor(grpc_middleware.ChainUnaryServer(loggingUnary, monitoringUnary, authUnary),
+	)
+
+These interceptors will be executed from left to right: logging, monitoring and auth.
+
+Here's an example for client side chaining:
+
+	clientConn, err = grpc.Dial(
+	    address,
+	        grpc.WithUnaryInterceptor(grpc_middleware.ChainUnaryClient(monitoringClientUnary, retryUnary)),
+	        grpc.WithStreamInterceptor(grpc_middleware.ChainStreamClient(monitoringClientStream, retryStream)),
+	)
+	client = pb_testproto.NewTestServiceClient(clientConn)
+	resp, err := client.PingEmpty(s.ctx, &myservice.Request{Msg: "hello"})
+
+These interceptors will be executed from left to right: monitoring and then retry logic.
+
+The retry interceptor will call every interceptor that follows it whenever when a retry happens.
+
+Writing Your Own
+
+Implementing your own interceptor is pretty trivial: there are interfaces for that. But the interesting
+bit exposing common data to handlers (and other middleware), similarly to HTTP Middleware design.
+For example, you may want to pass the identity of the caller from the auth interceptor all the way
+to the handling function.
+
+For example, a client side interceptor example for auth looks like:
+
+	func FakeAuthUnaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+	   newCtx := context.WithValue(ctx, "user_id", "john@example.com")
+	   return handler(newCtx, req)
+	}
+
+Unfortunately, it's not as easy for streaming RPCs. These have the `context.Context` embedded within
+the `grpc.ServerStream` object. To pass values through context, a wrapper (`WrappedServerStream`) is
+needed. For example:
+
+	func FakeAuthStreamingInterceptor(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+	   newStream := grpc_middleware.WrapServerStream(stream)
+	   newStream.WrappedContext = context.WithValue(ctx, "user_id", "john@example.com")
+	   return handler(srv, stream)
+	}
+*/
+package grpc_middleware
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/makefile b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/makefile
new file mode 100644
index 0000000..51dc5b8
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/makefile
@@ -0,0 +1,16 @@
+SHELL=/bin/bash
+
+GOFILES_NOVENDOR = $(shell go list ./... | grep -v /vendor/)
+
+all: vet fmt test
+
+fmt:
+	go fmt $(GOFILES_NOVENDOR)
+
+vet:
+	go vet $(GOFILES_NOVENDOR)
+
+test: vet
+	./scripts/test_all.sh
+
+.PHONY: all test
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/slack.png b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/slack.png
new file mode 100644
index 0000000..cc8f9a6
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/slack.png
Binary files differ
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/context.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/context.go
new file mode 100644
index 0000000..583025c
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/context.go
@@ -0,0 +1,78 @@
+package grpc_ctxtags
+
+import (
+	"context"
+)
+
+type ctxMarker struct{}
+
+var (
+	// ctxMarkerKey is the Context value marker used by *all* logging middleware.
+	// The logging middleware object must interf
+	ctxMarkerKey = &ctxMarker{}
+	// NoopTags is a trivial, minimum overhead implementation of Tags for which all operations are no-ops.
+	NoopTags = &noopTags{}
+)
+
+// Tags is the interface used for storing request tags between Context calls.
+// The default implementation is *not* thread safe, and should be handled only in the context of the request.
+type Tags interface {
+	// Set sets the given key in the metadata tags.
+	Set(key string, value interface{}) Tags
+	// Has checks if the given key exists.
+	Has(key string) bool
+	// Values returns a map of key to values.
+	// Do not modify the underlying map, please use Set instead.
+	Values() map[string]interface{}
+}
+
+type mapTags struct {
+	values map[string]interface{}
+}
+
+func (t *mapTags) Set(key string, value interface{}) Tags {
+	t.values[key] = value
+	return t
+}
+
+func (t *mapTags) Has(key string) bool {
+	_, ok := t.values[key]
+	return ok
+}
+
+func (t *mapTags) Values() map[string]interface{} {
+	return t.values
+}
+
+type noopTags struct{}
+
+func (t *noopTags) Set(key string, value interface{}) Tags {
+	return t
+}
+
+func (t *noopTags) Has(key string) bool {
+	return false
+}
+
+func (t *noopTags) Values() map[string]interface{} {
+	return nil
+}
+
+// Extracts returns a pre-existing Tags object in the Context.
+// If the context wasn't set in a tag interceptor, a no-op Tag storage is returned that will *not* be propagated in context.
+func Extract(ctx context.Context) Tags {
+	t, ok := ctx.Value(ctxMarkerKey).(Tags)
+	if !ok {
+		return NoopTags
+	}
+
+	return t
+}
+
+func setInContext(ctx context.Context, tags Tags) context.Context {
+	return context.WithValue(ctx, ctxMarkerKey, tags)
+}
+
+func newTags() Tags {
+	return &mapTags{values: make(map[string]interface{})}
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/doc.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/doc.go
new file mode 100644
index 0000000..960638d
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/doc.go
@@ -0,0 +1,22 @@
+/*
+`grpc_ctxtags` adds a Tag object to the context that can be used by other middleware to add context about a request.
+
+Request Context Tags
+
+Tags describe information about the request, and can be set and used by other middleware, or handlers. Tags are used
+for logging and tracing of requests. Tags are populated both upwards, *and* downwards in the interceptor-handler stack.
+
+You can automatically extract tags (in `grpc.request.<field_name>`) from request payloads.
+
+For unary and server-streaming methods, pass in the `WithFieldExtractor` option. For client-streams and bidirectional-streams, you can
+use `WithFieldExtractorForInitialReq` which will extract the tags from the first message passed from client to server.
+Note the tags will not be modified for subsequent requests, so this option only makes sense when the initial message
+establishes the meta-data for the stream.
+
+If a user doesn't use the interceptors that initialize the `Tags` object, all operations following from an `Extract(ctx)`
+will be no-ops. This is to ensure that code doesn't panic if the interceptors weren't used.
+
+Tags fields are typed, and shallow and should follow the OpenTracing semantics convention:
+https://github.com/opentracing/specification/blob/master/semantic_conventions.md
+*/
+package grpc_ctxtags
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/fieldextractor.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/fieldextractor.go
new file mode 100644
index 0000000..549ff48
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/fieldextractor.go
@@ -0,0 +1,85 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_ctxtags
+
+import (
+	"reflect"
+)
+
+// RequestFieldExtractorFunc is a user-provided function that extracts field information from a gRPC request.
+// It is called from tags middleware on arrival of unary request or a server-stream request.
+// Keys and values will be added to the context tags of the request. If there are no fields, you should return a nil.
+type RequestFieldExtractorFunc func(fullMethod string, req interface{}) map[string]interface{}
+
+type requestFieldsExtractor interface {
+	// ExtractRequestFields is a method declared on a Protobuf message that extracts fields from the interface.
+	// The values from the extracted fields should be set in the appendToMap, in order to avoid allocations.
+	ExtractRequestFields(appendToMap map[string]interface{})
+}
+
+// CodeGenRequestFieldExtractor is a function that relies on code-generated functions that export log fields from requests.
+// These are usually coming from a protoc-plugin that generates additional information based on custom field options.
+func CodeGenRequestFieldExtractor(fullMethod string, req interface{}) map[string]interface{} {
+	if ext, ok := req.(requestFieldsExtractor); ok {
+		retMap := make(map[string]interface{})
+		ext.ExtractRequestFields(retMap)
+		if len(retMap) == 0 {
+			return nil
+		}
+		return retMap
+	}
+	return nil
+}
+
+// TagBasedRequestFieldExtractor is a function that relies on Go struct tags to export log fields from requests.
+// These are usually coming from a protoc-plugin, such as Gogo protobuf.
+//
+//  message Metadata {
+//     repeated string tags = 1 [ (gogoproto.moretags) = "log_field:\"meta_tags\"" ];
+//  }
+//
+// The tagName is configurable using the tagName variable. Here it would be "log_field".
+func TagBasedRequestFieldExtractor(tagName string) RequestFieldExtractorFunc {
+	return func(fullMethod string, req interface{}) map[string]interface{} {
+		retMap := make(map[string]interface{})
+		reflectMessageTags(req, retMap, tagName)
+		if len(retMap) == 0 {
+			return nil
+		}
+		return retMap
+	}
+}
+
+func reflectMessageTags(msg interface{}, existingMap map[string]interface{}, tagName string) {
+	v := reflect.ValueOf(msg)
+	// Only deal with pointers to structs.
+	if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
+		return
+	}
+	// Deref the pointer get to the struct.
+	v = v.Elem()
+	t := v.Type()
+	for i := 0; i < v.NumField(); i++ {
+		field := v.Field(i)
+		kind := field.Kind()
+		// Only recurse down direct pointers, which should only be to nested structs.
+		if kind == reflect.Ptr {
+			reflectMessageTags(field.Interface(), existingMap, tagName)
+		}
+		// In case of arrays/splices (repeated fields) go down to the concrete type.
+		if kind == reflect.Array || kind == reflect.Slice {
+			if field.Len() == 0 {
+				continue
+			}
+			kind = field.Index(0).Kind()
+		}
+		// Only be interested in
+		if (kind >= reflect.Bool && kind <= reflect.Float64) || kind == reflect.String {
+			if tag := t.Field(i).Tag.Get(tagName); tag != "" {
+				existingMap[tag] = field.Interface()
+			}
+		}
+	}
+	return
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/interceptors.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/interceptors.go
new file mode 100644
index 0000000..038afd2
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/interceptors.go
@@ -0,0 +1,83 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_ctxtags
+
+import (
+	"github.com/grpc-ecosystem/go-grpc-middleware"
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/peer"
+)
+
+// UnaryServerInterceptor returns a new unary server interceptors that sets the values for request tags.
+func UnaryServerInterceptor(opts ...Option) grpc.UnaryServerInterceptor {
+	o := evaluateOptions(opts)
+	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+		newCtx := newTagsForCtx(ctx)
+		if o.requestFieldsFunc != nil {
+			setRequestFieldTags(newCtx, o.requestFieldsFunc, info.FullMethod, req)
+		}
+		return handler(newCtx, req)
+	}
+}
+
+// StreamServerInterceptor returns a new streaming server interceptor that sets the values for request tags.
+func StreamServerInterceptor(opts ...Option) grpc.StreamServerInterceptor {
+	o := evaluateOptions(opts)
+	return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+		newCtx := newTagsForCtx(stream.Context())
+		if o.requestFieldsFunc == nil {
+			// Short-circuit, don't do the expensive bit of allocating a wrappedStream.
+			wrappedStream := grpc_middleware.WrapServerStream(stream)
+			wrappedStream.WrappedContext = newCtx
+			return handler(srv, wrappedStream)
+		}
+		wrapped := &wrappedStream{stream, info, o, newCtx, true}
+		err := handler(srv, wrapped)
+		return err
+	}
+}
+
+// wrappedStream is a thin wrapper around grpc.ServerStream that allows modifying context and extracts log fields from the initial message.
+type wrappedStream struct {
+	grpc.ServerStream
+	info *grpc.StreamServerInfo
+	opts *options
+	// WrappedContext is the wrapper's own Context. You can assign it.
+	WrappedContext context.Context
+	initial        bool
+}
+
+// Context returns the wrapper's WrappedContext, overwriting the nested grpc.ServerStream.Context()
+func (w *wrappedStream) Context() context.Context {
+	return w.WrappedContext
+}
+
+func (w *wrappedStream) RecvMsg(m interface{}) error {
+	err := w.ServerStream.RecvMsg(m)
+	// We only do log fields extraction on the single-request of a server-side stream.
+	if !w.info.IsClientStream || w.opts.requestFieldsFromInitial && w.initial {
+		w.initial = false
+
+		setRequestFieldTags(w.Context(), w.opts.requestFieldsFunc, w.info.FullMethod, m)
+	}
+	return err
+}
+
+func newTagsForCtx(ctx context.Context) context.Context {
+	t := newTags()
+	if peer, ok := peer.FromContext(ctx); ok {
+		t.Set("peer.address", peer.Addr.String())
+	}
+	return setInContext(ctx, t)
+}
+
+func setRequestFieldTags(ctx context.Context, f RequestFieldExtractorFunc, fullMethodName string, req interface{}) {
+	if valMap := f(fullMethodName, req); valMap != nil {
+		t := Extract(ctx)
+		for k, v := range valMap {
+			t.Set("grpc.request."+k, v)
+		}
+	}
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/options.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/options.go
new file mode 100644
index 0000000..952775f
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/options.go
@@ -0,0 +1,44 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_ctxtags
+
+var (
+	defaultOptions = &options{
+		requestFieldsFunc: nil,
+	}
+)
+
+type options struct {
+	requestFieldsFunc        RequestFieldExtractorFunc
+	requestFieldsFromInitial bool
+}
+
+func evaluateOptions(opts []Option) *options {
+	optCopy := &options{}
+	*optCopy = *defaultOptions
+	for _, o := range opts {
+		o(optCopy)
+	}
+	return optCopy
+}
+
+type Option func(*options)
+
+// WithFieldExtractor customizes the function for extracting log fields from protobuf messages, for
+// unary and server-streamed methods only.
+func WithFieldExtractor(f RequestFieldExtractorFunc) Option {
+	return func(o *options) {
+		o.requestFieldsFunc = f
+	}
+}
+
+// WithFieldExtractorForInitialReq customizes the function for extracting log fields from protobuf messages,
+// for all unary and streaming methods. For client-streams and bidirectional-streams, the tags will be
+// extracted from the first message from the client.
+func WithFieldExtractorForInitialReq(f RequestFieldExtractorFunc) Option {
+	return func(o *options) {
+		o.requestFieldsFunc = f
+		o.requestFieldsFromInitial = true
+	}
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/client_interceptors.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/client_interceptors.go
new file mode 100644
index 0000000..f8fdecf
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/client_interceptors.go
@@ -0,0 +1,142 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_opentracing
+
+import (
+	"io"
+	"sync"
+
+	"github.com/grpc-ecosystem/go-grpc-middleware/util/metautils"
+	opentracing "github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/opentracing/opentracing-go/log"
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/metadata"
+)
+
+// UnaryClientInterceptor returns a new unary client interceptor for OpenTracing.
+func UnaryClientInterceptor(opts ...Option) grpc.UnaryClientInterceptor {
+	o := evaluateOptions(opts)
+	return func(parentCtx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+		if o.filterOutFunc != nil && !o.filterOutFunc(parentCtx, method) {
+			return invoker(parentCtx, method, req, reply, cc, opts...)
+		}
+		newCtx, clientSpan := newClientSpanFromContext(parentCtx, o.tracer, method)
+		err := invoker(newCtx, method, req, reply, cc, opts...)
+		finishClientSpan(clientSpan, err)
+		return err
+	}
+}
+
+// StreamClientInterceptor returns a new streaming client interceptor for OpenTracing.
+func StreamClientInterceptor(opts ...Option) grpc.StreamClientInterceptor {
+	o := evaluateOptions(opts)
+	return func(parentCtx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+		if o.filterOutFunc != nil && !o.filterOutFunc(parentCtx, method) {
+			return streamer(parentCtx, desc, cc, method, opts...)
+		}
+		newCtx, clientSpan := newClientSpanFromContext(parentCtx, o.tracer, method)
+		clientStream, err := streamer(newCtx, desc, cc, method, opts...)
+		if err != nil {
+			finishClientSpan(clientSpan, err)
+			return nil, err
+		}
+		return &tracedClientStream{ClientStream: clientStream, clientSpan: clientSpan}, nil
+	}
+}
+
+// type serverStreamingRetryingStream is the implementation of grpc.ClientStream that acts as a
+// proxy to the underlying call. If any of the RecvMsg() calls fail, it will try to reestablish
+// a new ClientStream according to the retry policy.
+type tracedClientStream struct {
+	grpc.ClientStream
+	mu              sync.Mutex
+	alreadyFinished bool
+	clientSpan      opentracing.Span
+}
+
+func (s *tracedClientStream) Header() (metadata.MD, error) {
+	h, err := s.ClientStream.Header()
+	if err != nil {
+		s.finishClientSpan(err)
+	}
+	return h, err
+}
+
+func (s *tracedClientStream) SendMsg(m interface{}) error {
+	err := s.ClientStream.SendMsg(m)
+	if err != nil {
+		s.finishClientSpan(err)
+	}
+	return err
+}
+
+func (s *tracedClientStream) CloseSend() error {
+	err := s.ClientStream.CloseSend()
+	if err != nil {
+		s.finishClientSpan(err)
+	}
+	return err
+}
+
+func (s *tracedClientStream) RecvMsg(m interface{}) error {
+	err := s.ClientStream.RecvMsg(m)
+	if err != nil {
+		s.finishClientSpan(err)
+	}
+	return err
+}
+
+func (s *tracedClientStream) finishClientSpan(err error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if !s.alreadyFinished {
+		finishClientSpan(s.clientSpan, err)
+		s.alreadyFinished = true
+	}
+}
+
+// ClientAddContextTags returns a context with specified opentracing tags, which
+// are used by UnaryClientInterceptor/StreamClientInterceptor when creating a
+// new span.
+func ClientAddContextTags(ctx context.Context, tags opentracing.Tags) context.Context {
+	return context.WithValue(ctx, clientSpanTagKey{}, tags)
+}
+
+type clientSpanTagKey struct{}
+
+func newClientSpanFromContext(ctx context.Context, tracer opentracing.Tracer, fullMethodName string) (context.Context, opentracing.Span) {
+	var parentSpanCtx opentracing.SpanContext
+	if parent := opentracing.SpanFromContext(ctx); parent != nil {
+		parentSpanCtx = parent.Context()
+	}
+	opts := []opentracing.StartSpanOption{
+		opentracing.ChildOf(parentSpanCtx),
+		ext.SpanKindRPCClient,
+		grpcTag,
+	}
+	if tagx := ctx.Value(clientSpanTagKey{}); tagx != nil {
+		if opt, ok := tagx.(opentracing.StartSpanOption); ok {
+			opts = append(opts, opt)
+		}
+	}
+	clientSpan := tracer.StartSpan(fullMethodName, opts...)
+	// Make sure we add this to the metadata of the call, so it gets propagated:
+	md := metautils.ExtractOutgoing(ctx).Clone()
+	if err := tracer.Inject(clientSpan.Context(), opentracing.HTTPHeaders, metadataTextMap(md)); err != nil {
+		grpclog.Printf("grpc_opentracing: failed serializing trace information: %v", err)
+	}
+	ctxWithMetadata := md.ToOutgoing(ctx)
+	return opentracing.ContextWithSpan(ctxWithMetadata, clientSpan), clientSpan
+}
+
+func finishClientSpan(clientSpan opentracing.Span, err error) {
+	if err != nil && err != io.EOF {
+		ext.Error.Set(clientSpan, true)
+		clientSpan.LogFields(log.String("event", "error"), log.String("message", err.Error()))
+	}
+	clientSpan.Finish()
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/doc.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/doc.go
new file mode 100644
index 0000000..7a58efc
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/doc.go
@@ -0,0 +1,22 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+/*
+`grpc_opentracing` adds OpenTracing
+
+OpenTracing Interceptors
+
+These are both client-side and server-side interceptors for OpenTracing. They are a provider-agnostic, with backends
+such as Zipkin, or Google Stackdriver Trace.
+
+For a service that sends out requests and receives requests, you *need* to use both, otherwise downstream requests will
+not have the appropriate requests propagated.
+
+All server-side spans are tagged with grpc_ctxtags information.
+
+For more information see:
+http://opentracing.io/documentation/
+https://github.com/opentracing/specification/blob/master/semantic_conventions.md
+
+*/
+package grpc_opentracing
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/id_extract.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/id_extract.go
new file mode 100644
index 0000000..d19f3c8
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/id_extract.go
@@ -0,0 +1,67 @@
+package grpc_opentracing
+
+import (
+	"strings"
+
+	grpc_ctxtags "github.com/grpc-ecosystem/go-grpc-middleware/tags"
+	opentracing "github.com/opentracing/opentracing-go"
+	"google.golang.org/grpc/grpclog"
+)
+
+const (
+	TagTraceId           = "trace.traceid"
+	TagSpanId            = "trace.spanid"
+	TagSampled           = "trace.sampled"
+	jaegerNotSampledFlag = "0"
+)
+
+// injectOpentracingIdsToTags writes trace data to ctxtags.
+// This is done in an incredibly hacky way, because the public-facing interface of opentracing doesn't give access to
+// the TraceId and SpanId of the SpanContext. Only the Tracer's Inject/Extract methods know what these are.
+// Most tracers have them encoded as keys with 'traceid' and 'spanid':
+// https://github.com/openzipkin/zipkin-go-opentracing/blob/594640b9ef7e5c994e8d9499359d693c032d738c/propagation_ot.go#L29
+// https://github.com/opentracing/basictracer-go/blob/1b32af207119a14b1b231d451df3ed04a72efebf/propagation_ot.go#L26
+// Jaeger from Uber use one-key schema with next format '{trace-id}:{span-id}:{parent-span-id}:{flags}'
+// https://www.jaegertracing.io/docs/client-libraries/#trace-span-identity
+func injectOpentracingIdsToTags(span opentracing.Span, tags grpc_ctxtags.Tags) {
+	if err := span.Tracer().Inject(span.Context(), opentracing.HTTPHeaders, &tagsCarrier{tags}); err != nil {
+		grpclog.Infof("grpc_opentracing: failed extracting trace info into ctx %v", err)
+	}
+}
+
+// tagsCarrier is a really hacky way of
+type tagsCarrier struct {
+	grpc_ctxtags.Tags
+}
+
+func (t *tagsCarrier) Set(key, val string) {
+	key = strings.ToLower(key)
+	if strings.Contains(key, "traceid") {
+		t.Tags.Set(TagTraceId, val) // this will most likely be base-16 (hex) encoded
+	}
+
+	if strings.Contains(key, "spanid") && !strings.Contains(strings.ToLower(key), "parent") {
+		t.Tags.Set(TagSpanId, val) // this will most likely be base-16 (hex) encoded
+	}
+
+	if strings.Contains(key, "sampled") {
+		switch val {
+		case "true", "false":
+			t.Tags.Set(TagSampled, val)
+		}
+	}
+
+	if key == "uber-trace-id" {
+		parts := strings.Split(val, ":")
+		if len(parts) == 4 {
+			t.Tags.Set(TagTraceId, parts[0])
+			t.Tags.Set(TagSpanId, parts[1])
+
+			if parts[3] != jaegerNotSampledFlag {
+				t.Tags.Set(TagSampled, "true")
+			} else {
+				t.Tags.Set(TagSampled, "false")
+			}
+		}
+	}
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/metadata.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/metadata.go
new file mode 100644
index 0000000..38f251d
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/metadata.go
@@ -0,0 +1,56 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_opentracing
+
+import (
+	"encoding/base64"
+	"strings"
+
+	"fmt"
+
+	"google.golang.org/grpc/metadata"
+)
+
+const (
+	binHdrSuffix = "-bin"
+)
+
+// metadataTextMap extends a metadata.MD to be an opentracing textmap
+type metadataTextMap metadata.MD
+
+// Set is a opentracing.TextMapReader interface that extracts values.
+func (m metadataTextMap) Set(key, val string) {
+	// gRPC allows for complex binary values to be written.
+	encodedKey, encodedVal := encodeKeyValue(key, val)
+	// The metadata object is a multimap, and previous values may exist, but for opentracing headers, we do not append
+	// we just override.
+	m[encodedKey] = []string{encodedVal}
+}
+
+// ForeachKey is a opentracing.TextMapReader interface that extracts values.
+func (m metadataTextMap) ForeachKey(callback func(key, val string) error) error {
+	for k, vv := range m {
+		for _, v := range vv {
+			if decodedKey, decodedVal, err := metadata.DecodeKeyValue(k, v); err == nil {
+				if err = callback(decodedKey, decodedVal); err != nil {
+					return err
+				}
+			} else {
+				return fmt.Errorf("failed decoding opentracing from gRPC metadata: %v", err)
+			}
+		}
+	}
+	return nil
+}
+
+// encodeKeyValue encodes key and value qualified for transmission via gRPC.
+// note: copy pasted from private values of grpc.metadata
+func encodeKeyValue(k, v string) (string, string) {
+	k = strings.ToLower(k)
+	if strings.HasSuffix(k, binHdrSuffix) {
+		val := base64.StdEncoding.EncodeToString([]byte(v))
+		v = string(val)
+	}
+	return k, v
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/options.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/options.go
new file mode 100644
index 0000000..e75102b
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/options.go
@@ -0,0 +1,55 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_opentracing
+
+import (
+	"context"
+
+	"github.com/opentracing/opentracing-go"
+)
+
+var (
+	defaultOptions = &options{
+		filterOutFunc: nil,
+		tracer:        nil,
+	}
+)
+
+// FilterFunc allows users to provide a function that filters out certain methods from being traced.
+//
+// If it returns false, the given request will not be traced.
+type FilterFunc func(ctx context.Context, fullMethodName string) bool
+
+type options struct {
+	filterOutFunc FilterFunc
+	tracer        opentracing.Tracer
+}
+
+func evaluateOptions(opts []Option) *options {
+	optCopy := &options{}
+	*optCopy = *defaultOptions
+	for _, o := range opts {
+		o(optCopy)
+	}
+	if optCopy.tracer == nil {
+		optCopy.tracer = opentracing.GlobalTracer()
+	}
+	return optCopy
+}
+
+type Option func(*options)
+
+// WithFilterFunc customizes the function used for deciding whether a given call is traced or not.
+func WithFilterFunc(f FilterFunc) Option {
+	return func(o *options) {
+		o.filterOutFunc = f
+	}
+}
+
+// WithTracer sets a custom tracer to be used for this middleware, otherwise the opentracing.GlobalTracer is used.
+func WithTracer(tracer opentracing.Tracer) Option {
+	return func(o *options) {
+		o.tracer = tracer
+	}
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/server_interceptors.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/server_interceptors.go
new file mode 100644
index 0000000..53764a0
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing/server_interceptors.go
@@ -0,0 +1,87 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_opentracing
+
+import (
+	"github.com/grpc-ecosystem/go-grpc-middleware"
+	"github.com/grpc-ecosystem/go-grpc-middleware/tags"
+	"github.com/grpc-ecosystem/go-grpc-middleware/util/metautils"
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/opentracing/opentracing-go/log"
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/grpclog"
+)
+
+var (
+	grpcTag = opentracing.Tag{Key: string(ext.Component), Value: "gRPC"}
+)
+
+// UnaryServerInterceptor returns a new unary server interceptor for OpenTracing.
+func UnaryServerInterceptor(opts ...Option) grpc.UnaryServerInterceptor {
+	o := evaluateOptions(opts)
+	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+		if o.filterOutFunc != nil && !o.filterOutFunc(ctx, info.FullMethod) {
+			return handler(ctx, req)
+		}
+		newCtx, serverSpan := newServerSpanFromInbound(ctx, o.tracer, info.FullMethod)
+		resp, err := handler(newCtx, req)
+		finishServerSpan(ctx, serverSpan, err)
+		return resp, err
+	}
+}
+
+// StreamServerInterceptor returns a new streaming server interceptor for OpenTracing.
+func StreamServerInterceptor(opts ...Option) grpc.StreamServerInterceptor {
+	o := evaluateOptions(opts)
+	return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+		if o.filterOutFunc != nil && !o.filterOutFunc(stream.Context(), info.FullMethod) {
+			return handler(srv, stream)
+		}
+		newCtx, serverSpan := newServerSpanFromInbound(stream.Context(), o.tracer, info.FullMethod)
+		wrappedStream := grpc_middleware.WrapServerStream(stream)
+		wrappedStream.WrappedContext = newCtx
+		err := handler(srv, wrappedStream)
+		finishServerSpan(newCtx, serverSpan, err)
+		return err
+	}
+}
+
+func newServerSpanFromInbound(ctx context.Context, tracer opentracing.Tracer, fullMethodName string) (context.Context, opentracing.Span) {
+	md := metautils.ExtractIncoming(ctx)
+	parentSpanContext, err := tracer.Extract(opentracing.HTTPHeaders, metadataTextMap(md))
+	if err != nil && err != opentracing.ErrSpanContextNotFound {
+		grpclog.Printf("grpc_opentracing: failed parsing trace information: %v", err)
+	}
+
+	serverSpan := tracer.StartSpan(
+		fullMethodName,
+		// this is magical, it attaches the new span to the parent parentSpanContext, and creates an unparented one if empty.
+		ext.RPCServerOption(parentSpanContext),
+		grpcTag,
+	)
+
+	injectOpentracingIdsToTags(serverSpan, grpc_ctxtags.Extract(ctx))
+	return opentracing.ContextWithSpan(ctx, serverSpan), serverSpan
+}
+
+func finishServerSpan(ctx context.Context, serverSpan opentracing.Span, err error) {
+	// Log context information
+	tags := grpc_ctxtags.Extract(ctx)
+	for k, v := range tags.Values() {
+		// Don't tag errors, log them instead.
+		if vErr, ok := v.(error); ok {
+			serverSpan.LogKV(k, vErr.Error())
+
+		} else {
+			serverSpan.SetTag(k, v)
+		}
+	}
+	if err != nil {
+		ext.Error.Set(serverSpan, true)
+		serverSpan.LogFields(log.String("event", "error"), log.String("message", err.Error()))
+	}
+	serverSpan.Finish()
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/doc.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/doc.go
new file mode 100644
index 0000000..1ed9bb4
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/doc.go
@@ -0,0 +1,19 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+/*
+Package `metautils` provides convenience functions for dealing with gRPC metadata.MD objects inside
+Context handlers.
+
+While the upstream grpc-go package contains decent functionality (see https://github.com/grpc/grpc-go/blob/master/Documentation/grpc-metadata.md)
+they are hard to use.
+
+The majority of functions center around the NiceMD, which is a convenience wrapper around metadata.MD. For example
+the following code allows you to easily extract incoming metadata (server handler) and put it into a new client context
+metadata.
+
+  nmd := metautils.ExtractIncoming(serverCtx).Clone(":authorization", ":custom")
+  clientCtx := nmd.Set("x-client-header", "2").Set("x-another", "3").ToOutgoing(ctx)
+*/
+
+package metautils
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/nicemd.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/nicemd.go
new file mode 100644
index 0000000..a277bee
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/nicemd.go
@@ -0,0 +1,126 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package metautils
+
+import (
+	"strings"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/metadata"
+)
+
+// NiceMD is a convenience wrapper definiting extra functions on the metadata.
+type NiceMD metadata.MD
+
+// ExtractIncoming extracts an inbound metadata from the server-side context.
+//
+// This function always returns a NiceMD wrapper of the metadata.MD, in case the context doesn't have metadata it returns
+// a new empty NiceMD.
+func ExtractIncoming(ctx context.Context) NiceMD {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return NiceMD(metadata.Pairs())
+	}
+	return NiceMD(md)
+}
+
+// ExtractOutgoing extracts an outbound metadata from the client-side context.
+//
+// This function always returns a NiceMD wrapper of the metadata.MD, in case the context doesn't have metadata it returns
+// a new empty NiceMD.
+func ExtractOutgoing(ctx context.Context) NiceMD {
+	md, ok := metadata.FromOutgoingContext(ctx)
+	if !ok {
+		return NiceMD(metadata.Pairs())
+	}
+	return NiceMD(md)
+}
+
+// Clone performs a *deep* copy of the metadata.MD.
+//
+// You can specify the lower-case copiedKeys to only copy certain whitelisted keys. If no keys are explicitly whitelisted
+// all keys get copied.
+func (m NiceMD) Clone(copiedKeys ...string) NiceMD {
+	newMd := NiceMD(metadata.Pairs())
+	for k, vv := range m {
+		found := false
+		if len(copiedKeys) == 0 {
+			found = true
+		} else {
+			for _, allowedKey := range copiedKeys {
+				if strings.ToLower(allowedKey) == strings.ToLower(k) {
+					found = true
+					break
+				}
+			}
+		}
+		if !found {
+			continue
+		}
+		newMd[k] = make([]string, len(vv))
+		copy(newMd[k], vv)
+	}
+	return NiceMD(newMd)
+}
+
+// ToOutgoing sets the given NiceMD as a client-side context for dispatching.
+func (m NiceMD) ToOutgoing(ctx context.Context) context.Context {
+	return metadata.NewOutgoingContext(ctx, metadata.MD(m))
+}
+
+// ToIncoming sets the given NiceMD as a server-side context for dispatching.
+//
+// This is mostly useful in ServerInterceptors..
+func (m NiceMD) ToIncoming(ctx context.Context) context.Context {
+	return metadata.NewIncomingContext(ctx, metadata.MD(m))
+}
+
+// Get retrieves a single value from the metadata.
+//
+// It works analogously to http.Header.Get, returning the first value if there are many set. If the value is not set,
+// an empty string is returned.
+//
+// The function is binary-key safe.
+func (m NiceMD) Get(key string) string {
+	k, _ := encodeKeyValue(key, "")
+	vv, ok := m[k]
+	if !ok {
+		return ""
+	}
+	return vv[0]
+}
+
+// Del retrieves a single value from the metadata.
+//
+// It works analogously to http.Header.Del, deleting all values if they exist.
+//
+// The function is binary-key safe.
+
+func (m NiceMD) Del(key string) NiceMD {
+	k, _ := encodeKeyValue(key, "")
+	delete(m, k)
+	return m
+}
+
+// Set sets the given value in a metadata.
+//
+// It works analogously to http.Header.Set, overwriting all previous metadata values.
+//
+// The function is binary-key safe.
+func (m NiceMD) Set(key string, value string) NiceMD {
+	k, v := encodeKeyValue(key, value)
+	m[k] = []string{v}
+	return m
+}
+
+// Add retrieves a single value from the metadata.
+//
+// It works analogously to http.Header.Add, as it appends to any existing values associated with key.
+//
+// The function is binary-key safe.
+func (m NiceMD) Add(key string, value string) NiceMD {
+	k, v := encodeKeyValue(key, value)
+	m[k] = append(m[k], v)
+	return m
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/single_key.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/single_key.go
new file mode 100644
index 0000000..8a53871
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/util/metautils/single_key.go
@@ -0,0 +1,22 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package metautils
+
+import (
+	"encoding/base64"
+	"strings"
+)
+
+const (
+	binHdrSuffix = "-bin"
+)
+
+func encodeKeyValue(k, v string) (string, string) {
+	k = strings.ToLower(k)
+	if strings.HasSuffix(k, binHdrSuffix) {
+		val := base64.StdEncoding.EncodeToString([]byte(v))
+		v = string(val)
+	}
+	return k, v
+}
diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/wrappers.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/wrappers.go
new file mode 100644
index 0000000..597b862
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/wrappers.go
@@ -0,0 +1,29 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_middleware
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+)
+
+// WrappedServerStream is a thin wrapper around grpc.ServerStream that allows modifying context.
+type WrappedServerStream struct {
+	grpc.ServerStream
+	// WrappedContext is the wrapper's own Context. You can assign it.
+	WrappedContext context.Context
+}
+
+// Context returns the wrapper's WrappedContext, overwriting the nested grpc.ServerStream.Context()
+func (w *WrappedServerStream) Context() context.Context {
+	return w.WrappedContext
+}
+
+// WrapServerStream returns a ServerStream that has the ability to overwrite context.
+func WrapServerStream(stream grpc.ServerStream) *WrappedServerStream {
+	if existing, ok := stream.(*WrappedServerStream); ok {
+		return existing
+	}
+	return &WrappedServerStream{ServerStream: stream, WrappedContext: stream.Context()}
+}
diff --git a/vendor/modules.txt b/vendor/modules.txt
index 9d67a93..fb9827a 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -46,6 +46,11 @@
 github.com/golang/snappy
 # github.com/google/uuid v1.1.1
 github.com/google/uuid
+# github.com/grpc-ecosystem/go-grpc-middleware v1.0.1-0.20190118093823-f849b5445de4
+github.com/grpc-ecosystem/go-grpc-middleware
+github.com/grpc-ecosystem/go-grpc-middleware/tags
+github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing
+github.com/grpc-ecosystem/go-grpc-middleware/util/metautils
 # github.com/hashicorp/consul/api v1.2.0
 github.com/hashicorp/consul/api
 # github.com/hashicorp/go-cleanhttp v0.5.1