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/*
*
* Copyright 2014, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
package transport
import (
"fmt"
"sync"
"golang.org/x/net/http2"
)
const (
// The default value of flow control window size in HTTP2 spec.
defaultWindowSize = 65535
// The initial window size for flow control.
initialWindowSize = defaultWindowSize // for an RPC
initialConnWindowSize = defaultWindowSize * 16 // for a connection
)
// The following defines various control items which could flow through
// the control buffer of transport. They represent different aspects of
// control tasks, e.g., flow control, settings, streaming resetting, etc.
type windowUpdate struct {
streamID uint32
increment uint32
}
func (windowUpdate) isItem() bool {
return true
}
type settings struct {
ack bool
ss []http2.Setting
}
func (settings) isItem() bool {
return true
}
type resetStream struct {
streamID uint32
code http2.ErrCode
}
func (resetStream) isItem() bool {
return true
}
type flushIO struct {
}
func (flushIO) isItem() bool {
return true
}
type ping struct {
ack bool
data [8]byte
}
func (ping) isItem() bool {
return true
}
// quotaPool is a pool which accumulates the quota and sends it to acquire()
// when it is available.
type quotaPool struct {
c chan int
mu sync.Mutex
quota int
}
// newQuotaPool creates a quotaPool which has quota q available to consume.
func newQuotaPool(q int) *quotaPool {
qb := &quotaPool{
c: make(chan int, 1),
}
if q > 0 {
qb.c <- q
} else {
qb.quota = q
}
return qb
}
// add adds n to the available quota and tries to send it on acquire.
func (qb *quotaPool) add(n int) {
qb.mu.Lock()
defer qb.mu.Unlock()
qb.quota += n
if qb.quota <= 0 {
return
}
select {
case qb.c <- qb.quota:
qb.quota = 0
default:
}
}
// cancel cancels the pending quota sent on acquire, if any.
func (qb *quotaPool) cancel() {
qb.mu.Lock()
defer qb.mu.Unlock()
select {
case n := <-qb.c:
qb.quota += n
default:
}
}
// reset cancels the pending quota sent on acquired, incremented by v and sends
// it back on acquire.
func (qb *quotaPool) reset(v int) {
qb.mu.Lock()
defer qb.mu.Unlock()
select {
case n := <-qb.c:
qb.quota += n
default:
}
qb.quota += v
if qb.quota <= 0 {
return
}
select {
case qb.c <- qb.quota:
qb.quota = 0
default:
}
}
// acquire returns the channel on which available quota amounts are sent.
func (qb *quotaPool) acquire() <-chan int {
return qb.c
}
// inFlow deals with inbound flow control
type inFlow struct {
// The inbound flow control limit for pending data.
limit uint32
// conn points to the shared connection-level inFlow that is shared
// by all streams on that conn. It is nil for the inFlow on the conn
// directly.
conn *inFlow
mu sync.Mutex
// pendingData is the overall data which have been received but not been
// consumed by applications.
pendingData uint32
// The amount of data the application has consumed but grpc has not sent
// window update for them. Used to reduce window update frequency.
pendingUpdate uint32
}
// onData is invoked when some data frame is received. It increments not only its
// own pendingData but also that of the associated connection-level flow.
func (f *inFlow) onData(n uint32) error {
if n == 0 {
return nil
}
f.mu.Lock()
defer f.mu.Unlock()
if f.pendingData+f.pendingUpdate+n > f.limit {
return fmt.Errorf("recieved %d-bytes data exceeding the limit %d bytes", f.pendingData+f.pendingUpdate+n, f.limit)
}
if f.conn != nil {
if err := f.conn.onData(n); err != nil {
return ConnectionErrorf("%v", err)
}
}
f.pendingData += n
return nil
}
// connOnRead updates the connection level states when the application consumes data.
func (f *inFlow) connOnRead(n uint32) uint32 {
if n == 0 || f.conn != nil {
return 0
}
f.mu.Lock()
defer f.mu.Unlock()
f.pendingData -= n
f.pendingUpdate += n
if f.pendingUpdate >= f.limit/4 {
ret := f.pendingUpdate
f.pendingUpdate = 0
return ret
}
return 0
}
// onRead is invoked when the application reads the data. It returns the window updates
// for both stream and connection level.
func (f *inFlow) onRead(n uint32) (swu, cwu uint32) {
if n == 0 {
return
}
f.mu.Lock()
defer f.mu.Unlock()
if f.pendingData == 0 {
// pendingData has been adjusted by restoreConn.
return
}
f.pendingData -= n
f.pendingUpdate += n
if f.pendingUpdate >= f.limit/4 {
swu = f.pendingUpdate
f.pendingUpdate = 0
}
cwu = f.conn.connOnRead(n)
return
}
// restoreConn is invoked when a stream is terminated. It removes its stake in
// the connection-level flow and resets its own state.
func (f *inFlow) restoreConn() uint32 {
if f.conn == nil {
return 0
}
f.mu.Lock()
defer f.mu.Unlock()
n := f.pendingData
f.pendingData = 0
f.pendingUpdate = 0
return f.conn.connOnRead(n)
}