initial add - go fmt on grpc
Change-Id: Ib0afadd2fe5571d1456a091f94f5644458f7d3f4
diff --git a/vendor/google.golang.org/grpc/internal/transport/bdp_estimator.go b/vendor/google.golang.org/grpc/internal/transport/bdp_estimator.go
new file mode 100644
index 0000000..070680e
--- /dev/null
+++ b/vendor/google.golang.org/grpc/internal/transport/bdp_estimator.go
@@ -0,0 +1,141 @@
+/*
+ *
+ * Copyright 2017 gRPC 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 transport
+
+import (
+ "sync"
+ "time"
+)
+
+const (
+ // bdpLimit is the maximum value the flow control windows will be increased
+ // to. TCP typically limits this to 4MB, but some systems go up to 16MB.
+ // Since this is only a limit, it is safe to make it optimistic.
+ bdpLimit = (1 << 20) * 16
+ // alpha is a constant factor used to keep a moving average
+ // of RTTs.
+ alpha = 0.9
+ // If the current bdp sample is greater than or equal to
+ // our beta * our estimated bdp and the current bandwidth
+ // sample is the maximum bandwidth observed so far, we
+ // increase our bbp estimate by a factor of gamma.
+ beta = 0.66
+ // To put our bdp to be smaller than or equal to twice the real BDP,
+ // we should multiply our current sample with 4/3, however to round things out
+ // we use 2 as the multiplication factor.
+ gamma = 2
+)
+
+// Adding arbitrary data to ping so that its ack can be identified.
+// Easter-egg: what does the ping message say?
+var bdpPing = &ping{data: [8]byte{2, 4, 16, 16, 9, 14, 7, 7}}
+
+type bdpEstimator struct {
+ // sentAt is the time when the ping was sent.
+ sentAt time.Time
+
+ mu sync.Mutex
+ // bdp is the current bdp estimate.
+ bdp uint32
+ // sample is the number of bytes received in one measurement cycle.
+ sample uint32
+ // bwMax is the maximum bandwidth noted so far (bytes/sec).
+ bwMax float64
+ // bool to keep track of the beginning of a new measurement cycle.
+ isSent bool
+ // Callback to update the window sizes.
+ updateFlowControl func(n uint32)
+ // sampleCount is the number of samples taken so far.
+ sampleCount uint64
+ // round trip time (seconds)
+ rtt float64
+}
+
+// timesnap registers the time bdp ping was sent out so that
+// network rtt can be calculated when its ack is received.
+// It is called (by controller) when the bdpPing is
+// being written on the wire.
+func (b *bdpEstimator) timesnap(d [8]byte) {
+ if bdpPing.data != d {
+ return
+ }
+ b.sentAt = time.Now()
+}
+
+// add adds bytes to the current sample for calculating bdp.
+// It returns true only if a ping must be sent. This can be used
+// by the caller (handleData) to make decision about batching
+// a window update with it.
+func (b *bdpEstimator) add(n uint32) bool {
+ b.mu.Lock()
+ defer b.mu.Unlock()
+ if b.bdp == bdpLimit {
+ return false
+ }
+ if !b.isSent {
+ b.isSent = true
+ b.sample = n
+ b.sentAt = time.Time{}
+ b.sampleCount++
+ return true
+ }
+ b.sample += n
+ return false
+}
+
+// calculate is called when an ack for a bdp ping is received.
+// Here we calculate the current bdp and bandwidth sample and
+// decide if the flow control windows should go up.
+func (b *bdpEstimator) calculate(d [8]byte) {
+ // Check if the ping acked for was the bdp ping.
+ if bdpPing.data != d {
+ return
+ }
+ b.mu.Lock()
+ rttSample := time.Since(b.sentAt).Seconds()
+ if b.sampleCount < 10 {
+ // Bootstrap rtt with an average of first 10 rtt samples.
+ b.rtt += (rttSample - b.rtt) / float64(b.sampleCount)
+ } else {
+ // Heed to the recent past more.
+ b.rtt += (rttSample - b.rtt) * float64(alpha)
+ }
+ b.isSent = false
+ // The number of bytes accumulated so far in the sample is smaller
+ // than or equal to 1.5 times the real BDP on a saturated connection.
+ bwCurrent := float64(b.sample) / (b.rtt * float64(1.5))
+ if bwCurrent > b.bwMax {
+ b.bwMax = bwCurrent
+ }
+ // If the current sample (which is smaller than or equal to the 1.5 times the real BDP) is
+ // greater than or equal to 2/3rd our perceived bdp AND this is the maximum bandwidth seen so far, we
+ // should update our perception of the network BDP.
+ if float64(b.sample) >= beta*float64(b.bdp) && bwCurrent == b.bwMax && b.bdp != bdpLimit {
+ sampleFloat := float64(b.sample)
+ b.bdp = uint32(gamma * sampleFloat)
+ if b.bdp > bdpLimit {
+ b.bdp = bdpLimit
+ }
+ bdp := b.bdp
+ b.mu.Unlock()
+ b.updateFlowControl(bdp)
+ return
+ }
+ b.mu.Unlock()
+}