writesched_random.go

Documentation: golang.org/x/net/http2

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package http2
     6  
     7  import "math"
     8  
     9  // NewRandomWriteScheduler constructs a WriteScheduler that ignores HTTP/2
    10  // priorities. Control frames like SETTINGS and PING are written before DATA
    11  // frames, but if no control frames are queued and multiple streams have queued
    12  // HEADERS or DATA frames, Pop selects a ready stream arbitrarily.
    13  func NewRandomWriteScheduler() WriteScheduler {
    14  	return &randomWriteScheduler{sq: make(map[uint32]*writeQueue)}
    15  }
    16  
    17  type randomWriteScheduler struct {
    18  	// zero are frames not associated with a specific stream.
    19  	zero writeQueue
    20  
    21  	// sq contains the stream-specific queues, keyed by stream ID.
    22  	// When a stream is idle, closed, or emptied, it's deleted
    23  	// from the map.
    24  	sq map[uint32]*writeQueue
    25  
    26  	// pool of empty queues for reuse.
    27  	queuePool writeQueuePool
    28  }
    29  
    30  func (ws *randomWriteScheduler) OpenStream(streamID uint32, options OpenStreamOptions) {
    31  	// no-op: idle streams are not tracked
    32  }
    33  
    34  func (ws *randomWriteScheduler) CloseStream(streamID uint32) {
    35  	q, ok := ws.sq[streamID]
    36  	if !ok {
    37  		return
    38  	}
    39  	delete(ws.sq, streamID)
    40  	ws.queuePool.put(q)
    41  }
    42  
    43  func (ws *randomWriteScheduler) AdjustStream(streamID uint32, priority PriorityParam) {
    44  	// no-op: priorities are ignored
    45  }
    46  
    47  func (ws *randomWriteScheduler) Push(wr FrameWriteRequest) {
    48  	if wr.isControl() {
    49  		ws.zero.push(wr)
    50  		return
    51  	}
    52  	id := wr.StreamID()
    53  	q, ok := ws.sq[id]
    54  	if !ok {
    55  		q = ws.queuePool.get()
    56  		ws.sq[id] = q
    57  	}
    58  	q.push(wr)
    59  }
    60  
    61  func (ws *randomWriteScheduler) Pop() (FrameWriteRequest, bool) {
    62  	// Control and RST_STREAM frames first.
    63  	if !ws.zero.empty() {
    64  		return ws.zero.shift(), true
    65  	}
    66  	// Iterate over all non-idle streams until finding one that can be consumed.
    67  	for streamID, q := range ws.sq {
    68  		if wr, ok := q.consume(math.MaxInt32); ok {
    69  			if q.empty() {
    70  				delete(ws.sq, streamID)
    71  				ws.queuePool.put(q)
    72  			}
    73  			return wr, true
    74  		}
    75  	}
    76  	return FrameWriteRequest{}, false
    77  }
    78
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