forked from yarpc/yarpc-go
-
Notifications
You must be signed in to change notification settings - Fork 0
/
heap.go
191 lines (161 loc) · 4.91 KB
/
heap.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
// Copyright (c) 2018 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package pendingheap
import (
"container/heap"
"context"
"sync"
"go.uber.org/yarpc/api/peer"
"go.uber.org/yarpc/api/transport"
)
type pendingHeap struct {
sync.Mutex
peers []*peerScore
// next is an incrementing counter for every push, which is compared when
// scores are equal. This ends up implementing round-robin when scores are
// equal.
next int
}
func (ph *pendingHeap) Choose(ctx context.Context, req *transport.Request) peer.StatusPeer {
ph.Lock()
ps, ok := ph.popPeer()
if !ok {
ph.Unlock()
return nil
}
// Note: We push the peer back to reset the "next" counter.
// This gives us round-robin behavior.
ph.pushPeer(ps)
ph.Unlock()
return ps.peer
}
func (ph *pendingHeap) Add(p peer.StatusPeer) peer.Subscriber {
if p == nil {
return nil
}
ps := &peerScore{peer: p, heap: ph}
ps.score = scorePeer(p)
ph.Lock()
ph.pushPeer(ps)
ph.Unlock()
return ps
}
func (ph *pendingHeap) Remove(p peer.StatusPeer, sub peer.Subscriber) {
ps, ok := sub.(*peerScore)
if !ok {
return
}
ph.Lock()
ph.delete(ps.index)
ph.Unlock()
}
func (ph *pendingHeap) notifyStatusChanged(ps *peerScore) {
status := ps.peer.Status()
ph.Lock()
ps.status = status
ps.score = scorePeer(ps.peer)
ph.update(ps.index)
ph.Unlock()
}
// Len must be called in the context of a lock, as it is indirectly called
// through heap.Push and heap.Pop.
func (ph *pendingHeap) Len() int {
return len(ph.peers)
}
// Less returns whether the left peer has a lower score. If the scores are
// equal, it returns the older peer (where "last" is lower.)
// Less must be called in the context of a lock, as it is indirectly called
// through heap.Push and heap.Pop.
func (ph *pendingHeap) Less(i, j int) bool {
p1 := ph.peers[i]
p2 := ph.peers[j]
if p1.score == p2.score {
return p1.last < p2.last
}
return p1.score < p2.score
}
// Swap implements the heap.Interface. Do NOT use this method directly.
// Swap must be called in the context of a lock, as it is indirectly called
// through heap.Push and heap.Pop.
func (ph *pendingHeap) Swap(i, j int) {
p1 := ph.peers[i]
p2 := ph.peers[j]
ph.peers[i], ph.peers[j] = ph.peers[j], ph.peers[i]
p1.index = j
p2.index = i
}
// Push implements the heap.Interface. Do NOT use this method directly.
// Use pushPeer instead.
// Push must be called in the context of a lock, as it is indirectly called
// through heap.Push.
func (ph *pendingHeap) Push(x interface{}) {
ps := x.(*peerScore)
ps.index = len(ph.peers)
ph.peers = append(ph.peers, ps)
}
// Pop implements the heap.Interface. Do NOT use this method directly.
// Use popPeer instead.
// Pop must be called in the context of a lock, as it is indirectly called
// through heap.Pop.
func (ph *pendingHeap) Pop() interface{} {
lastIndex := len(ph.peers) - 1
last := ph.peers[lastIndex]
ph.peers = ph.peers[:lastIndex]
return last
}
// delete removes the score at the given index.
// delete must be called in a lock.
func (ph *pendingHeap) delete(index int) {
// Swap the element we want to delete with the last element, then pop it off.
ph.Swap(index, ph.Len()-1)
ph.Pop()
// If the original index still exists in the list, it contains a different
// element so update the heap.
if index < ph.Len() {
ph.update(index)
}
}
// pushPeer must be called in the context of a lock.
func (ph *pendingHeap) pushPeer(ps *peerScore) {
ph.next++
ps.last = ph.next
heap.Push(ph, ps)
}
// popPeer must be called in the context of a lock.
func (ph *pendingHeap) popPeer() (*peerScore, bool) {
if ph.Len() == 0 {
return nil, false
}
peer := heap.Pop(ph).(*peerScore)
return peer, true
}
// update must be called in the context of a lock.
func (ph *pendingHeap) update(i int) {
heap.Fix(ph, i)
}
func (ph *pendingHeap) Start() error {
return nil
}
func (ph *pendingHeap) Stop() error {
return nil
}
func (ph *pendingHeap) IsRunning() bool {
return true
}