[VOL-2235] Mocks and interfaces for rw-core
This update consists of mocks that are used by the rw-core
during unit testing. It also includes interfaces used for unit
tests.
Change-Id: I20ca1455c358113c3aa897acc6355e0ddbc614b7
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go
new file mode 100644
index 0000000..cea5a90
--- /dev/null
+++ b/vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go
@@ -0,0 +1,349 @@
+// Copyright 2016 The Prometheus Authors
+// 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
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package promhttp provides tooling around HTTP servers and clients.
+//
+// First, the package allows the creation of http.Handler instances to expose
+// Prometheus metrics via HTTP. promhttp.Handler acts on the
+// prometheus.DefaultGatherer. With HandlerFor, you can create a handler for a
+// custom registry or anything that implements the Gatherer interface. It also
+// allows the creation of handlers that act differently on errors or allow to
+// log errors.
+//
+// Second, the package provides tooling to instrument instances of http.Handler
+// via middleware. Middleware wrappers follow the naming scheme
+// InstrumentHandlerX, where X describes the intended use of the middleware.
+// See each function's doc comment for specific details.
+//
+// Finally, the package allows for an http.RoundTripper to be instrumented via
+// middleware. Middleware wrappers follow the naming scheme
+// InstrumentRoundTripperX, where X describes the intended use of the
+// middleware. See each function's doc comment for specific details.
+package promhttp
+
+import (
+ "compress/gzip"
+ "fmt"
+ "io"
+ "net/http"
+ "strings"
+ "sync"
+ "time"
+
+ "github.com/prometheus/common/expfmt"
+
+ "github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+ contentTypeHeader = "Content-Type"
+ contentEncodingHeader = "Content-Encoding"
+ acceptEncodingHeader = "Accept-Encoding"
+)
+
+var gzipPool = sync.Pool{
+ New: func() interface{} {
+ return gzip.NewWriter(nil)
+ },
+}
+
+// Handler returns an http.Handler for the prometheus.DefaultGatherer, using
+// default HandlerOpts, i.e. it reports the first error as an HTTP error, it has
+// no error logging, and it applies compression if requested by the client.
+//
+// The returned http.Handler is already instrumented using the
+// InstrumentMetricHandler function and the prometheus.DefaultRegisterer. If you
+// create multiple http.Handlers by separate calls of the Handler function, the
+// metrics used for instrumentation will be shared between them, providing
+// global scrape counts.
+//
+// This function is meant to cover the bulk of basic use cases. If you are doing
+// anything that requires more customization (including using a non-default
+// Gatherer, different instrumentation, and non-default HandlerOpts), use the
+// HandlerFor function. See there for details.
+func Handler() http.Handler {
+ return InstrumentMetricHandler(
+ prometheus.DefaultRegisterer, HandlerFor(prometheus.DefaultGatherer, HandlerOpts{}),
+ )
+}
+
+// HandlerFor returns an uninstrumented http.Handler for the provided
+// Gatherer. The behavior of the Handler is defined by the provided
+// HandlerOpts. Thus, HandlerFor is useful to create http.Handlers for custom
+// Gatherers, with non-default HandlerOpts, and/or with custom (or no)
+// instrumentation. Use the InstrumentMetricHandler function to apply the same
+// kind of instrumentation as it is used by the Handler function.
+func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
+ var (
+ inFlightSem chan struct{}
+ errCnt = prometheus.NewCounterVec(
+ prometheus.CounterOpts{
+ Name: "promhttp_metric_handler_errors_total",
+ Help: "Total number of internal errors encountered by the promhttp metric handler.",
+ },
+ []string{"cause"},
+ )
+ )
+
+ if opts.MaxRequestsInFlight > 0 {
+ inFlightSem = make(chan struct{}, opts.MaxRequestsInFlight)
+ }
+ if opts.Registry != nil {
+ // Initialize all possibilites that can occur below.
+ errCnt.WithLabelValues("gathering")
+ errCnt.WithLabelValues("encoding")
+ if err := opts.Registry.Register(errCnt); err != nil {
+ if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+ errCnt = are.ExistingCollector.(*prometheus.CounterVec)
+ } else {
+ panic(err)
+ }
+ }
+ }
+
+ h := http.HandlerFunc(func(rsp http.ResponseWriter, req *http.Request) {
+ if inFlightSem != nil {
+ select {
+ case inFlightSem <- struct{}{}: // All good, carry on.
+ defer func() { <-inFlightSem }()
+ default:
+ http.Error(rsp, fmt.Sprintf(
+ "Limit of concurrent requests reached (%d), try again later.", opts.MaxRequestsInFlight,
+ ), http.StatusServiceUnavailable)
+ return
+ }
+ }
+ mfs, err := reg.Gather()
+ if err != nil {
+ if opts.ErrorLog != nil {
+ opts.ErrorLog.Println("error gathering metrics:", err)
+ }
+ errCnt.WithLabelValues("gathering").Inc()
+ switch opts.ErrorHandling {
+ case PanicOnError:
+ panic(err)
+ case ContinueOnError:
+ if len(mfs) == 0 {
+ // Still report the error if no metrics have been gathered.
+ httpError(rsp, err)
+ return
+ }
+ case HTTPErrorOnError:
+ httpError(rsp, err)
+ return
+ }
+ }
+
+ contentType := expfmt.Negotiate(req.Header)
+ header := rsp.Header()
+ header.Set(contentTypeHeader, string(contentType))
+
+ w := io.Writer(rsp)
+ if !opts.DisableCompression && gzipAccepted(req.Header) {
+ header.Set(contentEncodingHeader, "gzip")
+ gz := gzipPool.Get().(*gzip.Writer)
+ defer gzipPool.Put(gz)
+
+ gz.Reset(w)
+ defer gz.Close()
+
+ w = gz
+ }
+
+ enc := expfmt.NewEncoder(w, contentType)
+
+ var lastErr error
+ for _, mf := range mfs {
+ if err := enc.Encode(mf); err != nil {
+ lastErr = err
+ if opts.ErrorLog != nil {
+ opts.ErrorLog.Println("error encoding and sending metric family:", err)
+ }
+ errCnt.WithLabelValues("encoding").Inc()
+ switch opts.ErrorHandling {
+ case PanicOnError:
+ panic(err)
+ case ContinueOnError:
+ // Handled later.
+ case HTTPErrorOnError:
+ httpError(rsp, err)
+ return
+ }
+ }
+ }
+
+ if lastErr != nil {
+ httpError(rsp, lastErr)
+ }
+ })
+
+ if opts.Timeout <= 0 {
+ return h
+ }
+ return http.TimeoutHandler(h, opts.Timeout, fmt.Sprintf(
+ "Exceeded configured timeout of %v.\n",
+ opts.Timeout,
+ ))
+}
+
+// InstrumentMetricHandler is usually used with an http.Handler returned by the
+// HandlerFor function. It instruments the provided http.Handler with two
+// metrics: A counter vector "promhttp_metric_handler_requests_total" to count
+// scrapes partitioned by HTTP status code, and a gauge
+// "promhttp_metric_handler_requests_in_flight" to track the number of
+// simultaneous scrapes. This function idempotently registers collectors for
+// both metrics with the provided Registerer. It panics if the registration
+// fails. The provided metrics are useful to see how many scrapes hit the
+// monitored target (which could be from different Prometheus servers or other
+// scrapers), and how often they overlap (which would result in more than one
+// scrape in flight at the same time). Note that the scrapes-in-flight gauge
+// will contain the scrape by which it is exposed, while the scrape counter will
+// only get incremented after the scrape is complete (as only then the status
+// code is known). For tracking scrape durations, use the
+// "scrape_duration_seconds" gauge created by the Prometheus server upon each
+// scrape.
+func InstrumentMetricHandler(reg prometheus.Registerer, handler http.Handler) http.Handler {
+ cnt := prometheus.NewCounterVec(
+ prometheus.CounterOpts{
+ Name: "promhttp_metric_handler_requests_total",
+ Help: "Total number of scrapes by HTTP status code.",
+ },
+ []string{"code"},
+ )
+ // Initialize the most likely HTTP status codes.
+ cnt.WithLabelValues("200")
+ cnt.WithLabelValues("500")
+ cnt.WithLabelValues("503")
+ if err := reg.Register(cnt); err != nil {
+ if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+ cnt = are.ExistingCollector.(*prometheus.CounterVec)
+ } else {
+ panic(err)
+ }
+ }
+
+ gge := prometheus.NewGauge(prometheus.GaugeOpts{
+ Name: "promhttp_metric_handler_requests_in_flight",
+ Help: "Current number of scrapes being served.",
+ })
+ if err := reg.Register(gge); err != nil {
+ if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+ gge = are.ExistingCollector.(prometheus.Gauge)
+ } else {
+ panic(err)
+ }
+ }
+
+ return InstrumentHandlerCounter(cnt, InstrumentHandlerInFlight(gge, handler))
+}
+
+// HandlerErrorHandling defines how a Handler serving metrics will handle
+// errors.
+type HandlerErrorHandling int
+
+// These constants cause handlers serving metrics to behave as described if
+// errors are encountered.
+const (
+ // Serve an HTTP status code 500 upon the first error
+ // encountered. Report the error message in the body.
+ HTTPErrorOnError HandlerErrorHandling = iota
+ // Ignore errors and try to serve as many metrics as possible. However,
+ // if no metrics can be served, serve an HTTP status code 500 and the
+ // last error message in the body. Only use this in deliberate "best
+ // effort" metrics collection scenarios. In this case, it is highly
+ // recommended to provide other means of detecting errors: By setting an
+ // ErrorLog in HandlerOpts, the errors are logged. By providing a
+ // Registry in HandlerOpts, the exposed metrics include an error counter
+ // "promhttp_metric_handler_errors_total", which can be used for
+ // alerts.
+ ContinueOnError
+ // Panic upon the first error encountered (useful for "crash only" apps).
+ PanicOnError
+)
+
+// Logger is the minimal interface HandlerOpts needs for logging. Note that
+// log.Logger from the standard library implements this interface, and it is
+// easy to implement by custom loggers, if they don't do so already anyway.
+type Logger interface {
+ Println(v ...interface{})
+}
+
+// HandlerOpts specifies options how to serve metrics via an http.Handler. The
+// zero value of HandlerOpts is a reasonable default.
+type HandlerOpts struct {
+ // ErrorLog specifies an optional logger for errors collecting and
+ // serving metrics. If nil, errors are not logged at all.
+ ErrorLog Logger
+ // ErrorHandling defines how errors are handled. Note that errors are
+ // logged regardless of the configured ErrorHandling provided ErrorLog
+ // is not nil.
+ ErrorHandling HandlerErrorHandling
+ // If Registry is not nil, it is used to register a metric
+ // "promhttp_metric_handler_errors_total", partitioned by "cause". A
+ // failed registration causes a panic. Note that this error counter is
+ // different from the instrumentation you get from the various
+ // InstrumentHandler... helpers. It counts errors that don't necessarily
+ // result in a non-2xx HTTP status code. There are two typical cases:
+ // (1) Encoding errors that only happen after streaming of the HTTP body
+ // has already started (and the status code 200 has been sent). This
+ // should only happen with custom collectors. (2) Collection errors with
+ // no effect on the HTTP status code because ErrorHandling is set to
+ // ContinueOnError.
+ Registry prometheus.Registerer
+ // If DisableCompression is true, the handler will never compress the
+ // response, even if requested by the client.
+ DisableCompression bool
+ // The number of concurrent HTTP requests is limited to
+ // MaxRequestsInFlight. Additional requests are responded to with 503
+ // Service Unavailable and a suitable message in the body. If
+ // MaxRequestsInFlight is 0 or negative, no limit is applied.
+ MaxRequestsInFlight int
+ // If handling a request takes longer than Timeout, it is responded to
+ // with 503 ServiceUnavailable and a suitable Message. No timeout is
+ // applied if Timeout is 0 or negative. Note that with the current
+ // implementation, reaching the timeout simply ends the HTTP requests as
+ // described above (and even that only if sending of the body hasn't
+ // started yet), while the bulk work of gathering all the metrics keeps
+ // running in the background (with the eventual result to be thrown
+ // away). Until the implementation is improved, it is recommended to
+ // implement a separate timeout in potentially slow Collectors.
+ Timeout time.Duration
+}
+
+// gzipAccepted returns whether the client will accept gzip-encoded content.
+func gzipAccepted(header http.Header) bool {
+ a := header.Get(acceptEncodingHeader)
+ parts := strings.Split(a, ",")
+ for _, part := range parts {
+ part = strings.TrimSpace(part)
+ if part == "gzip" || strings.HasPrefix(part, "gzip;") {
+ return true
+ }
+ }
+ return false
+}
+
+// httpError removes any content-encoding header and then calls http.Error with
+// the provided error and http.StatusInternalServerErrer. Error contents is
+// supposed to be uncompressed plain text. However, same as with a plain
+// http.Error, any header settings will be void if the header has already been
+// sent. The error message will still be written to the writer, but it will
+// probably be of limited use.
+func httpError(rsp http.ResponseWriter, err error) {
+ rsp.Header().Del(contentEncodingHeader)
+ http.Error(
+ rsp,
+ "An error has occurred while serving metrics:\n\n"+err.Error(),
+ http.StatusInternalServerError,
+ )
+}