forked from ethereum/go-ethereum
-
Notifications
You must be signed in to change notification settings - Fork 2
/
subscription.go
136 lines (120 loc) · 4.44 KB
/
subscription.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
// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package rpc
import (
"context"
"errors"
"sync"
)
var (
// ErrNotificationsUnsupported is returned when the connection doesn't support notifications
ErrNotificationsUnsupported = errors.New("notifications not supported")
// ErrNotificationNotFound is returned when the notification for the given id is not found
ErrSubscriptionNotFound = errors.New("subscription not found")
)
// ID defines a pseudo random number that is used to identify RPC subscriptions.
type ID string
// a Subscription is created by a notifier and tight to that notifier. The client can use
// this subscription to wait for an unsubscribe request for the client, see Err().
type Subscription struct {
ID ID
namespace string
err chan error // closed on unsubscribe
}
// Err returns a channel that is closed when the client send an unsubscribe request.
func (s *Subscription) Err() <-chan error {
return s.err
}
// notifierKey is used to store a notifier within the connection context.
type notifierKey struct{}
// Notifier is tight to a RPC connection that supports subscriptions.
// Server callbacks use the notifier to send notifications.
type Notifier struct {
codec ServerCodec
subMu sync.RWMutex // guards active and inactive maps
stopped bool
active map[ID]*Subscription
inactive map[ID]*Subscription
}
// newNotifier creates a new notifier that can be used to send subscription
// notifications to the client.
func newNotifier(codec ServerCodec) *Notifier {
return &Notifier{
codec: codec,
active: make(map[ID]*Subscription),
inactive: make(map[ID]*Subscription),
}
}
// NotifierFromContext returns the Notifier value stored in ctx, if any.
func NotifierFromContext(ctx context.Context) (*Notifier, bool) {
n, ok := ctx.Value(notifierKey{}).(*Notifier)
return n, ok
}
// CreateSubscription returns a new subscription that is coupled to the
// RPC connection. By default subscriptions are inactive and notifications
// are dropped until the subscription is marked as active. This is done
// by the RPC server after the subscription ID is send to the client.
func (n *Notifier) CreateSubscription() *Subscription {
s := &Subscription{ID: NewID(), err: make(chan error)}
n.subMu.Lock()
n.inactive[s.ID] = s
n.subMu.Unlock()
return s
}
// Notify sends a notification to the client with the given data as payload.
// If an error occurs the RPC connection is closed and the error is returned.
func (n *Notifier) Notify(id ID, data interface{}) error {
n.subMu.RLock()
defer n.subMu.RUnlock()
sub, active := n.active[id]
if active {
notification := n.codec.CreateNotification(string(id), sub.namespace, data)
if err := n.codec.Write(notification); err != nil {
n.codec.Close()
return err
}
}
return nil
}
// Closed returns a channel that is closed when the RPC connection is closed.
func (n *Notifier) Closed() <-chan interface{} {
return n.codec.Closed()
}
// unsubscribe a subscription.
// If the subscription could not be found ErrSubscriptionNotFound is returned.
func (n *Notifier) unsubscribe(id ID) error {
n.subMu.Lock()
defer n.subMu.Unlock()
if s, found := n.active[id]; found {
close(s.err)
delete(n.active, id)
return nil
}
return ErrSubscriptionNotFound
}
// activate enables a subscription. Until a subscription is enabled all
// notifications are dropped. This method is called by the RPC server after
// the subscription ID was sent to client. This prevents notifications being
// send to the client before the subscription ID is send to the client.
func (n *Notifier) activate(id ID, namespace string) {
n.subMu.Lock()
defer n.subMu.Unlock()
if sub, found := n.inactive[id]; found {
sub.namespace = namespace
n.active[id] = sub
delete(n.inactive, id)
}
}