-
Notifications
You must be signed in to change notification settings - Fork 0
/
peer_request_queue.go
310 lines (258 loc) · 7.45 KB
/
peer_request_queue.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
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
package decision
import (
"sync"
"time"
wantlist "github.com/ipfs/go-ipfs/exchange/bitswap/wantlist"
pq "github.com/ipfs/go-ipfs/thirdparty/pq"
cid "gx/ipfs/QmcTcsTvfaeEBRFo1TkFgT8sRmgi1n1LTZpecfVP8fzpGD/go-cid"
peer "gx/ipfs/QmfMmLGoKzCHDN7cGgk64PJr4iipzidDRME8HABSJqvmhC/go-libp2p-peer"
)
type peerRequestQueue interface {
// Pop returns the next peerRequestTask. Returns nil if the peerRequestQueue is empty.
Pop() *peerRequestTask
Push(entry *wantlist.Entry, to peer.ID)
Remove(k *cid.Cid, p peer.ID)
// NB: cannot expose simply expose taskQueue.Len because trashed elements
// may exist. These trashed elements should not contribute to the count.
}
func newPRQ() *prq {
return &prq{
taskMap: make(map[string]*peerRequestTask),
partners: make(map[peer.ID]*activePartner),
frozen: make(map[peer.ID]*activePartner),
pQueue: pq.New(partnerCompare),
}
}
// verify interface implementation
var _ peerRequestQueue = &prq{}
// TODO: at some point, the strategy needs to plug in here
// to help decide how to sort tasks (on add) and how to select
// tasks (on getnext). For now, we are assuming a dumb/nice strategy.
type prq struct {
lock sync.Mutex
pQueue pq.PQ
taskMap map[string]*peerRequestTask
partners map[peer.ID]*activePartner
frozen map[peer.ID]*activePartner
}
// Push currently adds a new peerRequestTask to the end of the list
func (tl *prq) Push(entry *wantlist.Entry, to peer.ID) {
tl.lock.Lock()
defer tl.lock.Unlock()
partner, ok := tl.partners[to]
if !ok {
partner = newActivePartner()
tl.pQueue.Push(partner)
tl.partners[to] = partner
}
partner.activelk.Lock()
defer partner.activelk.Unlock()
if partner.activeBlocks.Has(entry.Cid) {
return
}
if task, ok := tl.taskMap[taskKey(to, entry.Cid)]; ok {
task.Entry.Priority = entry.Priority
partner.taskQueue.Update(task.index)
return
}
task := &peerRequestTask{
Entry: entry,
Target: to,
created: time.Now(),
Done: func() {
tl.lock.Lock()
partner.TaskDone(entry.Cid)
tl.pQueue.Update(partner.Index())
tl.lock.Unlock()
},
}
partner.taskQueue.Push(task)
tl.taskMap[task.Key()] = task
partner.requests++
tl.pQueue.Update(partner.Index())
}
// Pop 'pops' the next task to be performed. Returns nil if no task exists.
func (tl *prq) Pop() *peerRequestTask {
tl.lock.Lock()
defer tl.lock.Unlock()
if tl.pQueue.Len() == 0 {
return nil
}
partner := tl.pQueue.Pop().(*activePartner)
var out *peerRequestTask
for partner.taskQueue.Len() > 0 && partner.freezeVal == 0 {
out = partner.taskQueue.Pop().(*peerRequestTask)
delete(tl.taskMap, out.Key())
if out.trash {
out = nil
continue // discarding tasks that have been removed
}
partner.StartTask(out.Entry.Cid)
partner.requests--
break // and return |out|
}
tl.pQueue.Push(partner)
return out
}
// Remove removes a task from the queue
func (tl *prq) Remove(k *cid.Cid, p peer.ID) {
tl.lock.Lock()
t, ok := tl.taskMap[taskKey(p, k)]
if ok {
// remove the task "lazily"
// simply mark it as trash, so it'll be dropped when popped off the
// queue.
t.trash = true
// having canceled a block, we now account for that in the given partner
partner := tl.partners[p]
partner.requests--
// we now also 'freeze' that partner. If they sent us a cancel for a
// block we were about to send them, we should wait a short period of time
// to make sure we receive any other in-flight cancels before sending
// them a block they already potentially have
if partner.freezeVal == 0 {
tl.frozen[p] = partner
}
partner.freezeVal++
tl.pQueue.Update(partner.index)
}
tl.lock.Unlock()
}
func (tl *prq) fullThaw() {
tl.lock.Lock()
defer tl.lock.Unlock()
for id, partner := range tl.frozen {
partner.freezeVal = 0
delete(tl.frozen, id)
tl.pQueue.Update(partner.index)
}
}
func (tl *prq) thawRound() {
tl.lock.Lock()
defer tl.lock.Unlock()
for id, partner := range tl.frozen {
partner.freezeVal -= (partner.freezeVal + 1) / 2
if partner.freezeVal <= 0 {
delete(tl.frozen, id)
}
tl.pQueue.Update(partner.index)
}
}
type peerRequestTask struct {
Entry *wantlist.Entry
Target peer.ID
// A callback to signal that this task has been completed
Done func()
// trash in a book-keeping field
trash bool
// created marks the time that the task was added to the queue
created time.Time
index int // book-keeping field used by the pq container
}
// Key uniquely identifies a task.
func (t *peerRequestTask) Key() string {
return taskKey(t.Target, t.Entry.Cid)
}
// Index implements pq.Elem
func (t *peerRequestTask) Index() int {
return t.index
}
// SetIndex implements pq.Elem
func (t *peerRequestTask) SetIndex(i int) {
t.index = i
}
// taskKey returns a key that uniquely identifies a task.
func taskKey(p peer.ID, k *cid.Cid) string {
return string(p) + k.KeyString()
}
// FIFO is a basic task comparator that returns tasks in the order created.
var FIFO = func(a, b *peerRequestTask) bool {
return a.created.Before(b.created)
}
// V1 respects the target peer's wantlist priority. For tasks involving
// different peers, the oldest task is prioritized.
var V1 = func(a, b *peerRequestTask) bool {
if a.Target == b.Target {
return a.Entry.Priority > b.Entry.Priority
}
return FIFO(a, b)
}
func wrapCmp(f func(a, b *peerRequestTask) bool) func(a, b pq.Elem) bool {
return func(a, b pq.Elem) bool {
return f(a.(*peerRequestTask), b.(*peerRequestTask))
}
}
type activePartner struct {
// Active is the number of blocks this peer is currently being sent
// active must be locked around as it will be updated externally
activelk sync.Mutex
active int
activeBlocks *cid.Set
// requests is the number of blocks this peer is currently requesting
// request need not be locked around as it will only be modified under
// the peerRequestQueue's locks
requests int
// for the PQ interface
index int
freezeVal int
// priority queue of tasks belonging to this peer
taskQueue pq.PQ
}
func newActivePartner() *activePartner {
return &activePartner{
taskQueue: pq.New(wrapCmp(V1)),
activeBlocks: cid.NewSet(),
}
}
// partnerCompare implements pq.ElemComparator
// returns true if peer 'a' has higher priority than peer 'b'
func partnerCompare(a, b pq.Elem) bool {
pa := a.(*activePartner)
pb := b.(*activePartner)
// having no blocks in their wantlist means lowest priority
// having both of these checks ensures stability of the sort
if pa.requests == 0 {
return false
}
if pb.requests == 0 {
return true
}
if pa.freezeVal > pb.freezeVal {
return false
}
if pa.freezeVal < pb.freezeVal {
return true
}
if pa.active == pb.active {
// sorting by taskQueue.Len() aids in cleaning out trash entries faster
// if we sorted instead by requests, one peer could potentially build up
// a huge number of cancelled entries in the queue resulting in a memory leak
return pa.taskQueue.Len() > pb.taskQueue.Len()
}
return pa.active < pb.active
}
// StartTask signals that a task was started for this partner
func (p *activePartner) StartTask(k *cid.Cid) {
p.activelk.Lock()
p.activeBlocks.Add(k)
p.active++
p.activelk.Unlock()
}
// TaskDone signals that a task was completed for this partner
func (p *activePartner) TaskDone(k *cid.Cid) {
p.activelk.Lock()
p.activeBlocks.Remove(k)
p.active--
if p.active < 0 {
panic("more tasks finished than started!")
}
p.activelk.Unlock()
}
// Index implements pq.Elem
func (p *activePartner) Index() int {
return p.index
}
// SetIndex implements pq.Elem
func (p *activePartner) SetIndex(i int) {
p.index = i
}