120 lines
2.7 KiB
Go
120 lines
2.7 KiB
Go
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// Copyright 2023 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package http2
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import (
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"fmt"
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"math"
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)
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type roundRobinWriteScheduler struct {
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// control contains control frames (SETTINGS, PING, etc.).
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control writeQueue
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// streams maps stream ID to a queue.
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streams map[uint32]*writeQueue
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// stream queues are stored in a circular linked list.
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// head is the next stream to write, or nil if there are no streams open.
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head *writeQueue
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// pool of empty queues for reuse.
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queuePool writeQueuePool
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}
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// newRoundRobinWriteScheduler constructs a new write scheduler.
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// The round robin scheduler priorizes control frames
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// like SETTINGS and PING over DATA frames.
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// When there are no control frames to send, it performs a round-robin
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// selection from the ready streams.
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func newRoundRobinWriteScheduler() WriteScheduler {
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ws := &roundRobinWriteScheduler{
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streams: make(map[uint32]*writeQueue),
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}
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return ws
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}
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func (ws *roundRobinWriteScheduler) OpenStream(streamID uint32, options OpenStreamOptions) {
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if ws.streams[streamID] != nil {
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panic(fmt.Errorf("stream %d already opened", streamID))
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}
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q := ws.queuePool.get()
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ws.streams[streamID] = q
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if ws.head == nil {
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ws.head = q
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q.next = q
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q.prev = q
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} else {
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// Queues are stored in a ring.
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// Insert the new stream before ws.head, putting it at the end of the list.
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q.prev = ws.head.prev
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q.next = ws.head
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q.prev.next = q
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q.next.prev = q
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}
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}
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func (ws *roundRobinWriteScheduler) CloseStream(streamID uint32) {
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q := ws.streams[streamID]
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if q == nil {
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return
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}
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if q.next == q {
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// This was the only open stream.
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ws.head = nil
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} else {
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q.prev.next = q.next
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q.next.prev = q.prev
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if ws.head == q {
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ws.head = q.next
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}
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}
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delete(ws.streams, streamID)
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ws.queuePool.put(q)
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}
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func (ws *roundRobinWriteScheduler) AdjustStream(streamID uint32, priority PriorityParam) {}
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func (ws *roundRobinWriteScheduler) Push(wr FrameWriteRequest) {
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if wr.isControl() {
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ws.control.push(wr)
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return
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}
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q := ws.streams[wr.StreamID()]
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if q == nil {
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// This is a closed stream.
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// wr should not be a HEADERS or DATA frame.
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// We push the request onto the control queue.
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if wr.DataSize() > 0 {
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panic("add DATA on non-open stream")
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}
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ws.control.push(wr)
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return
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}
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q.push(wr)
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}
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func (ws *roundRobinWriteScheduler) Pop() (FrameWriteRequest, bool) {
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// Control and RST_STREAM frames first.
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if !ws.control.empty() {
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return ws.control.shift(), true
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}
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if ws.head == nil {
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return FrameWriteRequest{}, false
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}
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q := ws.head
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for {
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if wr, ok := q.consume(math.MaxInt32); ok {
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ws.head = q.next
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return wr, true
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}
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q = q.next
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if q == ws.head {
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break
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}
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}
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return FrameWriteRequest{}, false
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}
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