forked from ipfs/kubo
-
Notifications
You must be signed in to change notification settings - Fork 0
/
notifications.go
130 lines (110 loc) · 2.62 KB
/
notifications.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
package notifications
import (
"context"
"sync"
blocks "gx/ipfs/QmTRCUvZLiir12Qr6MV3HKfKMHX8Nf1Vddn6t2g5nsQSb9/go-block-format"
cid "gx/ipfs/QmapdYm1b22Frv3k17fqrBYTFRxwiaVJkB299Mfn33edeB/go-cid"
pubsub "gx/ipfs/QmdbxjQWogRCHRaxhhGnYdT1oQJzL9GdqSKzCdqWr85AP2/pubsub"
)
const bufferSize = 16
type PubSub interface {
Publish(block blocks.Block)
Subscribe(ctx context.Context, keys ...*cid.Cid) <-chan blocks.Block
Shutdown()
}
func New() PubSub {
return &impl{
wrapped: *pubsub.New(bufferSize),
cancel: make(chan struct{}),
}
}
type impl struct {
wrapped pubsub.PubSub
// These two fields make up a shutdown "lock".
// We need them as calling, e.g., `Unsubscribe` after calling `Shutdown`
// blocks forever and fixing this in pubsub would be rather invasive.
cancel chan struct{}
wg sync.WaitGroup
}
func (ps *impl) Publish(block blocks.Block) {
ps.wg.Add(1)
defer ps.wg.Done()
select {
case <-ps.cancel:
// Already shutdown, bail.
return
default:
}
ps.wrapped.Pub(block, block.Cid().KeyString())
}
// Not safe to call more than once.
func (ps *impl) Shutdown() {
// Interrupt in-progress subscriptions.
close(ps.cancel)
// Wait for them to finish.
ps.wg.Wait()
// shutdown the pubsub.
ps.wrapped.Shutdown()
}
// Subscribe returns a channel of blocks for the given |keys|. |blockChannel|
// is closed if the |ctx| times out or is cancelled, or after sending len(keys)
// blocks.
func (ps *impl) Subscribe(ctx context.Context, keys ...*cid.Cid) <-chan blocks.Block {
blocksCh := make(chan blocks.Block, len(keys))
valuesCh := make(chan interface{}, len(keys)) // provide our own channel to control buffer, prevent blocking
if len(keys) == 0 {
close(blocksCh)
return blocksCh
}
// prevent shutdown
ps.wg.Add(1)
// check if shutdown *after* preventing shutdowns.
select {
case <-ps.cancel:
// abort, allow shutdown to continue.
ps.wg.Done()
close(blocksCh)
return blocksCh
default:
}
ps.wrapped.AddSubOnceEach(valuesCh, toStrings(keys)...)
go func() {
defer func() {
ps.wrapped.Unsub(valuesCh)
close(blocksCh)
// Unblock shutdown.
ps.wg.Done()
}()
for {
select {
case <-ps.cancel:
return
case <-ctx.Done():
return
case val, ok := <-valuesCh:
if !ok {
return
}
block, ok := val.(blocks.Block)
if !ok {
return
}
select {
case <-ps.cancel:
return
case <-ctx.Done():
return
case blocksCh <- block: // continue
}
}
}
}()
return blocksCh
}
func toStrings(keys []*cid.Cid) []string {
strs := make([]string, 0, len(keys))
for _, key := range keys {
strs = append(strs, key.KeyString())
}
return strs
}