252 lines
7.2 KiB
Go
252 lines
7.2 KiB
Go
/*
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*
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* Copyright 2014, Google Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Google Inc. nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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package transport
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import (
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"fmt"
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"math"
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"sync"
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"time"
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"golang.org/x/net/http2"
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)
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const (
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// The default value of flow control window size in HTTP2 spec.
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defaultWindowSize = 65535
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// The initial window size for flow control.
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initialWindowSize = defaultWindowSize // for an RPC
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initialConnWindowSize = defaultWindowSize * 16 // for a connection
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infinity = time.Duration(math.MaxInt64)
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defaultClientKeepaliveTime = infinity
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defaultClientKeepaliveTimeout = time.Duration(20 * time.Second)
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defaultMaxStreamsClient = 100
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defaultMaxConnectionIdle = infinity
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defaultMaxConnectionAge = infinity
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defaultMaxConnectionAgeGrace = infinity
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defaultServerKeepaliveTime = time.Duration(2 * time.Hour)
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defaultServerKeepaliveTimeout = time.Duration(20 * time.Second)
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defaultKeepalivePolicyMinTime = time.Duration(5 * time.Minute)
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// max window limit set by HTTP2 Specs.
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maxWindowSize = math.MaxInt32
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)
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// The following defines various control items which could flow through
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// the control buffer of transport. They represent different aspects of
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// control tasks, e.g., flow control, settings, streaming resetting, etc.
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type windowUpdate struct {
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streamID uint32
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increment uint32
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flush bool
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}
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func (*windowUpdate) item() {}
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type settings struct {
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ack bool
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ss []http2.Setting
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}
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func (*settings) item() {}
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type resetStream struct {
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streamID uint32
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code http2.ErrCode
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}
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func (*resetStream) item() {}
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type goAway struct {
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code http2.ErrCode
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debugData []byte
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}
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func (*goAway) item() {}
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type flushIO struct {
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}
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func (*flushIO) item() {}
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type ping struct {
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ack bool
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data [8]byte
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}
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func (*ping) item() {}
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// quotaPool is a pool which accumulates the quota and sends it to acquire()
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// when it is available.
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type quotaPool struct {
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c chan int
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mu sync.Mutex
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quota int
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}
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// newQuotaPool creates a quotaPool which has quota q available to consume.
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func newQuotaPool(q int) *quotaPool {
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qb := "aPool{
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c: make(chan int, 1),
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}
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if q > 0 {
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qb.c <- q
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} else {
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qb.quota = q
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}
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return qb
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}
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// add cancels the pending quota sent on acquired, incremented by v and sends
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// it back on acquire.
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func (qb *quotaPool) add(v int) {
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qb.mu.Lock()
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defer qb.mu.Unlock()
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select {
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case n := <-qb.c:
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qb.quota += n
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default:
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}
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qb.quota += v
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if qb.quota <= 0 {
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return
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}
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// After the pool has been created, this is the only place that sends on
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// the channel. Since mu is held at this point and any quota that was sent
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// on the channel has been retrieved, we know that this code will always
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// place any positive quota value on the channel.
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select {
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case qb.c <- qb.quota:
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qb.quota = 0
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default:
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}
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}
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// acquire returns the channel on which available quota amounts are sent.
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func (qb *quotaPool) acquire() <-chan int {
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return qb.c
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}
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// inFlow deals with inbound flow control
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type inFlow struct {
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// The inbound flow control limit for pending data.
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limit uint32
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mu sync.Mutex
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// pendingData is the overall data which have been received but not been
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// consumed by applications.
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pendingData uint32
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// The amount of data the application has consumed but grpc has not sent
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// window update for them. Used to reduce window update frequency.
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pendingUpdate uint32
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// delta is the extra window update given by receiver when an application
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// is reading data bigger in size than the inFlow limit.
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delta uint32
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}
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func (f *inFlow) maybeAdjust(n uint32) uint32 {
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if n > uint32(math.MaxInt32) {
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n = uint32(math.MaxInt32)
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}
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f.mu.Lock()
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defer f.mu.Unlock()
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// estSenderQuota is the receiver's view of the maximum number of bytes the sender
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// can send without a window update.
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estSenderQuota := int32(f.limit - (f.pendingData + f.pendingUpdate))
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// estUntransmittedData is the maximum number of bytes the sends might not have put
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// on the wire yet. A value of 0 or less means that we have already received all or
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// more bytes than the application is requesting to read.
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estUntransmittedData := int32(n - f.pendingData) // Casting into int32 since it could be negative.
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// This implies that unless we send a window update, the sender won't be able to send all the bytes
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// for this message. Therefore we must send an update over the limit since there's an active read
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// request from the application.
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if estUntransmittedData > estSenderQuota {
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// Sender's window shouldn't go more than 2^31 - 1 as speecified in the HTTP spec.
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if f.limit+n > maxWindowSize {
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f.delta = maxWindowSize - f.limit
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} else {
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// Send a window update for the whole message and not just the difference between
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// estUntransmittedData and estSenderQuota. This will be helpful in case the message
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// is padded; We will fallback on the current available window(at least a 1/4th of the limit).
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f.delta = n
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}
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return f.delta
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}
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return 0
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}
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// onData is invoked when some data frame is received. It updates pendingData.
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func (f *inFlow) onData(n uint32) error {
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f.mu.Lock()
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defer f.mu.Unlock()
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f.pendingData += n
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if f.pendingData+f.pendingUpdate > f.limit+f.delta {
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return fmt.Errorf("received %d-bytes data exceeding the limit %d bytes", f.pendingData+f.pendingUpdate, f.limit)
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}
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return nil
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}
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// onRead is invoked when the application reads the data. It returns the window size
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// to be sent to the peer.
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func (f *inFlow) onRead(n uint32) uint32 {
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f.mu.Lock()
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defer f.mu.Unlock()
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if f.pendingData == 0 {
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return 0
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}
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f.pendingData -= n
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if n > f.delta {
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n -= f.delta
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f.delta = 0
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} else {
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f.delta -= n
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n = 0
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}
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f.pendingUpdate += n
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if f.pendingUpdate >= f.limit/4 {
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wu := f.pendingUpdate
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f.pendingUpdate = 0
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return wu
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}
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return 0
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}
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func (f *inFlow) resetPendingUpdate() uint32 {
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f.mu.Lock()
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defer f.mu.Unlock()
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n := f.pendingUpdate
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f.pendingUpdate = 0
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return n
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}
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