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