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rpc: refactor subscriptions and filters

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This commit is contained in:
Bas van Kervel
2016-07-27 17:47:46 +02:00
committed by Bas van Kervel
parent 3b39d4d1c1
commit 47ff813012
15 changed files with 1304 additions and 1255 deletions
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297
rpc/notification.go
View File

@ -1,297 +0,0 @@
// 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 (
"errors"
"sync"
"time"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
"golang.org/x/net/context"
)
var (
// ErrNotificationsUnsupported is returned when the connection doesn't support notifications
ErrNotificationsUnsupported = errors.New("subscription notifications not supported by the current transport")
// ErrNotificationNotFound is returned when the notification for the given id is not found
ErrNotificationNotFound = errors.New("notification not found")
// errNotifierStopped is returned when the notifier is stopped (e.g. codec is closed)
errNotifierStopped = errors.New("unable to send notification")
// errNotificationQueueFull is returns when there are too many notifications in the queue
errNotificationQueueFull = errors.New("too many pending notifications")
)
// unsubSignal is a signal that the subscription is unsubscribed. It is used to flush buffered
// notifications that might be pending in the internal queue.
var unsubSignal = new(struct{})
// UnsubscribeCallback defines a callback that is called when a subcription ends.
// It receives the subscription id as argument.
type UnsubscribeCallback func(id string)
// notification is a helper object that holds event data for a subscription
type notification struct {
sub *bufferedSubscription // subscription id
data interface{} // event data
}
// A Notifier type describes the interface for objects that can send create subscriptions
type Notifier interface {
// Create a new subscription. The given callback is called when this subscription
// is cancelled (e.g. client send an unsubscribe, connection closed).
NewSubscription(UnsubscribeCallback) (Subscription, error)
// Cancel subscription
Unsubscribe(id string) error
}
type notifierKey struct{}
// 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
}
// Subscription defines the interface for objects that can notify subscribers
type Subscription interface {
// Inform client of an event
Notify(data interface{}) error
// Unique identifier
ID() string
// Cancel subscription
Cancel() error
}
// bufferedSubscription is a subscription that uses a bufferedNotifier to send
// notifications to subscribers.
type bufferedSubscription struct {
id string
unsubOnce sync.Once // call unsub method once
unsub UnsubscribeCallback // called on Unsubscribed
notifier *bufferedNotifier // forward notifications to
pending chan interface{} // closed when active
flushed chan interface{} // closed when all buffered notifications are send
lastNotification time.Time // last time a notification was send
}
// ID returns the subscription identifier that the client uses to refer to this instance.
func (s *bufferedSubscription) ID() string {
return s.id
}
// Cancel informs the notifier that this subscription is cancelled by the API
func (s *bufferedSubscription) Cancel() error {
return s.notifier.Unsubscribe(s.id)
}
// Notify the subscriber of a particular event.
func (s *bufferedSubscription) Notify(data interface{}) error {
return s.notifier.send(s.id, data)
}
// bufferedNotifier is a notifier that queues notifications in an internal queue and
// send them as fast as possible to the client from this queue. It will stop if the
// queue grows past a given size.
type bufferedNotifier struct {
codec ServerCodec // underlying connection
mu sync.Mutex // guard internal state
subscriptions map[string]*bufferedSubscription // keep track of subscriptions associated with codec
queueSize int // max number of items in queue
queue chan *notification // notification queue
stopped bool // indication if this notifier is ordered to stop
}
// newBufferedNotifier returns a notifier that queues notifications in an internal queue
// from which notifications are send as fast as possible to the client. If the queue size
// limit is reached (client is unable to keep up) it will stop and closes the codec.
func newBufferedNotifier(codec ServerCodec, size int) *bufferedNotifier {
notifier := &bufferedNotifier{
codec: codec,
subscriptions: make(map[string]*bufferedSubscription),
queue: make(chan *notification, size),
queueSize: size,
}
go notifier.run()
return notifier
}
// NewSubscription creates a new subscription that forwards events to this instance internal
// queue. The given callback is called when the subscription is unsubscribed/cancelled.
func (n *bufferedNotifier) NewSubscription(callback UnsubscribeCallback) (Subscription, error) {
id, err := newSubscriptionID()
if err != nil {
return nil, err
}
n.mu.Lock()
defer n.mu.Unlock()
if n.stopped {
return nil, errNotifierStopped
}
sub := &bufferedSubscription{
id: id,
unsub: callback,
notifier: n,
pending: make(chan interface{}),
flushed: make(chan interface{}),
lastNotification: time.Now(),
}
n.subscriptions[id] = sub
return sub, nil
}
// Remove the given subscription. If subscription is not found notificationNotFoundErr is returned.
func (n *bufferedNotifier) Unsubscribe(subid string) error {
n.mu.Lock()
sub, found := n.subscriptions[subid]
n.mu.Unlock()
if found {
// send the unsubscribe signal, this will cause the notifier not to accept new events
// for this subscription and will close the flushed channel after the last (buffered)
// notification was send to the client.
if err := n.send(subid, unsubSignal); err != nil {
return err
}
// wait for confirmation that all (buffered) events are send for this subscription.
// this ensures that the unsubscribe method response is not send before all buffered
// events for this subscription are send.
<-sub.flushed
return nil
}
return ErrNotificationNotFound
}
// Send enques the given data for the subscription with public ID on the internal queue. t returns
// an error when the notifier is stopped or the queue is full. If data is the unsubscribe signal it
// will remove the subscription with the given id from the subscription collection.
func (n *bufferedNotifier) send(id string, data interface{}) error {
n.mu.Lock()
defer n.mu.Unlock()
if n.stopped {
return errNotifierStopped
}
var (
subscription *bufferedSubscription
found bool
)
// check if subscription is associated with this connection, it might be cancelled
// (subscribe/connection closed)
if subscription, found = n.subscriptions[id]; !found {
glog.V(logger.Error).Infof("received notification for unknown subscription %s\n", id)
return ErrNotificationNotFound
}
// received the unsubscribe signal. Add it to the queue to make sure any pending notifications
// for this subscription are send. When the run loop receives this singal it will signal that
// all pending subscriptions are flushed and that the confirmation of the unsubscribe can be
// send to the user. Remove the subscriptions to make sure new notifications are not accepted.
if data == unsubSignal {
delete(n.subscriptions, id)
if subscription.unsub != nil {
subscription.unsubOnce.Do(func() { subscription.unsub(id) })
}
}
subscription.lastNotification = time.Now()
if len(n.queue) >= n.queueSize {
glog.V(logger.Warn).Infoln("too many buffered notifications -> close connection")
n.codec.Close()
return errNotificationQueueFull
}
n.queue <- &notification{subscription, data}
return nil
}
// run reads notifications from the internal queue and sends them to the client. In case of an
// error, or when the codec is closed it will cancel all active subscriptions and returns.
func (n *bufferedNotifier) run() {
defer func() {
n.mu.Lock()
defer n.mu.Unlock()
n.stopped = true
close(n.queue)
// on exit call unsubscribe callback
for id, sub := range n.subscriptions {
if sub.unsub != nil {
sub.unsubOnce.Do(func() { sub.unsub(id) })
}
close(sub.flushed)
delete(n.subscriptions, id)
}
}()
for {
select {
case notification := <-n.queue:
// It can happen that an event is raised before the RPC server was able to send the sub
// id to the client. Therefore subscriptions are marked as pending until the sub id was
// send. The RPC server will activate the subscription by closing the pending chan.
<-notification.sub.pending
if notification.data == unsubSignal {
// unsubSignal is the last accepted message for this subscription. Raise the signal
// that all buffered notifications are sent by closing the flushed channel. This
// indicates that the response for the unsubscribe can be send to the client.
close(notification.sub.flushed)
} else {
msg := n.codec.CreateNotification(notification.sub.id, notification.data)
if err := n.codec.Write(msg); err != nil {
n.codec.Close()
// unable to send notification to client, unsubscribe all subscriptions
glog.V(logger.Warn).Infof("unable to send notification - %v\n", err)
return
}
}
case <-n.codec.Closed(): // connection was closed
glog.V(logger.Debug).Infoln("codec closed, stop subscriptions")
return
}
}
}
// Marks the subscription as active. This will causes the notifications for this subscription to be
// forwarded to the client.
func (n *bufferedNotifier) activate(subid string) {
n.mu.Lock()
defer n.mu.Unlock()
if sub, found := n.subscriptions[subid]; found {
close(sub.pending)
}
}

12
rpc/server.go
View File

@ -166,7 +166,7 @@ func (s *Server) serveRequest(codec ServerCodec, singleShot bool, options CodecO
// to send notification to clients. It is thight to the codec/connection. If the
// connection is closed the notifier will stop and cancels all active subscriptions.
if options&OptionSubscriptions == OptionSubscriptions {
ctx = context.WithValue(ctx, notifierKey{}, newBufferedNotifier(codec, notificationBufferSize))
ctx = context.WithValue(ctx, notifierKey{}, newNotifier(codec))
}
s.codecsMu.Lock()
if atomic.LoadInt32(&s.run) != 1 { // server stopped
@ -247,7 +247,7 @@ func (s *Server) Stop() {
}
// createSubscription will call the subscription callback and returns the subscription id or error.
func (s *Server) createSubscription(ctx context.Context, c ServerCodec, req *serverRequest) (string, error) {
func (s *Server) createSubscription(ctx context.Context, c ServerCodec, req *serverRequest) (ID, error) {
// subscription have as first argument the context following optional arguments
args := []reflect.Value{req.callb.rcvr, reflect.ValueOf(ctx)}
args = append(args, req.args...)
@ -257,7 +257,7 @@ func (s *Server) createSubscription(ctx context.Context, c ServerCodec, req *ser
return "", reply[1].Interface().(error)
}
return reply[0].Interface().(Subscription).ID(), nil
return reply[0].Interface().(*Subscription).ID, nil
}
// handle executes a request and returns the response from the callback.
@ -273,8 +273,8 @@ func (s *Server) handle(ctx context.Context, codec ServerCodec, req *serverReque
return codec.CreateErrorResponse(&req.id, &callbackError{ErrNotificationsUnsupported.Error()}), nil
}
subid := req.args[0].String()
if err := notifier.Unsubscribe(subid); err != nil {
subid := ID(req.args[0].String())
if err := notifier.unsubscribe(subid); err != nil {
return codec.CreateErrorResponse(&req.id, &callbackError{err.Error()}), nil
}
@ -292,7 +292,7 @@ func (s *Server) handle(ctx context.Context, codec ServerCodec, req *serverReque
// active the subscription after the sub id was successfully sent to the client
activateSub := func() {
notifier, _ := NotifierFromContext(ctx)
notifier.(*bufferedNotifier).activate(subid)
notifier.activate(subid)
}
return codec.CreateResponse(req.id, subid), activateSub

2
rpc/server_test.go
View File

@ -72,7 +72,7 @@ func (s *Service) InvalidRets3() (string, string, error) {
return "", "", nil
}
func (s *Service) Subscription(ctx context.Context) (Subscription, error) {
func (s *Service) Subscription(ctx context.Context) (*Subscription, error) {
return nil, nil
}

135
rpc/subscription.go Normal file
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@ -0,0 +1,135 @@
// 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 (
"errors"
"sync"
"golang.org/x/net/context"
)
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 psuedo 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
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{NewID(), 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()
_, active := n.active[id]
if active {
notification := n.codec.CreateNotification(string(id), 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) {
n.subMu.Lock()
defer n.subMu.Unlock()
if sub, found := n.inactive[id]; found {
n.active[id] = sub
delete(n.inactive, id)
}
}

34
rpc/notification_test.go → rpc/subscription_test.go
View File

@ -50,7 +50,7 @@ func (s *NotificationTestService) Unsubscribe(subid string) {
s.mu.Unlock()
}
func (s *NotificationTestService) SomeSubscription(ctx context.Context, n, val int) (Subscription, error) {
func (s *NotificationTestService) SomeSubscription(ctx context.Context, n, val int) (*Subscription, error) {
notifier, supported := NotifierFromContext(ctx)
if !supported {
return nil, ErrNotificationsUnsupported
@ -59,17 +59,29 @@ func (s *NotificationTestService) SomeSubscription(ctx context.Context, n, val i
// by explicitly creating an subscription we make sure that the subscription id is send back to the client
// before the first subscription.Notify is called. Otherwise the events might be send before the response
// for the eth_subscribe method.
subscription, err := notifier.NewSubscription(s.Unsubscribe)
if err != nil {
return nil, err
}
subscription := notifier.CreateSubscription()
go func() {
// test expects n events, if we begin sending event immediatly some events
// will probably be dropped since the subscription ID might not be send to
// the client.
time.Sleep(5 * time.Second)
for i := 0; i < n; i++ {
if err := subscription.Notify(val + i); err != nil {
if err := notifier.Notify(subscription.ID, val+i); err != nil {
return
}
}
select {
case <-notifier.Closed():
s.mu.Lock()
s.unsubscribed = true
s.mu.Unlock()
case <-subscription.Err():
s.mu.Lock()
s.unsubscribed = true
s.mu.Unlock()
}
}()
return subscription, nil
@ -77,7 +89,7 @@ func (s *NotificationTestService) SomeSubscription(ctx context.Context, n, val i
// HangSubscription blocks on s.unblockHangSubscription before
// sending anything.
func (s *NotificationTestService) HangSubscription(ctx context.Context, val int) (Subscription, error) {
func (s *NotificationTestService) HangSubscription(ctx context.Context, val int) (*Subscription, error) {
notifier, supported := NotifierFromContext(ctx)
if !supported {
return nil, ErrNotificationsUnsupported
@ -85,12 +97,10 @@ func (s *NotificationTestService) HangSubscription(ctx context.Context, val int)
s.gotHangSubscriptionReq <- struct{}{}
<-s.unblockHangSubscription
subscription, err := notifier.NewSubscription(s.Unsubscribe)
if err != nil {
return nil, err
}
subscription := notifier.CreateSubscription()
go func() {
subscription.Notify(val)
notifier.Notify(subscription.ID, val)
}()
return subscription, nil
}

4
rpc/types.go
View File

@ -269,6 +269,6 @@ func (bn *BlockNumber) UnmarshalJSON(data []byte) error {
return fmt.Errorf("blocknumber not in range [%d, %d]", earliestBlockNumber, maxBlockNumber)
}
func (bn *BlockNumber) Int64() int64 {
return (int64)(*bn)
func (bn BlockNumber) Int64() int64 {
return (int64)(bn)
}

42
rpc/utils.go
View File

@ -17,17 +17,26 @@
package rpc
import (
"crypto/rand"
"bufio"
crand "crypto/rand"
"encoding/binary"
"encoding/hex"
"errors"
"math/big"
"math/rand"
"reflect"
"sync"
"time"
"unicode"
"unicode/utf8"
"golang.org/x/net/context"
)
var (
subscriptionIDGenMu sync.Mutex
subscriptionIDGen = idGenerator()
)
// Is this an exported - upper case - name?
func isExported(name string) bool {
rune, _ := utf8.DecodeRuneInString(name)
@ -218,11 +227,28 @@ METHODS:
return callbacks, subscriptions
}
func newSubscriptionID() (string, error) {
var subid [16]byte
n, _ := rand.Read(subid[:])
if n != 16 {
return "", errors.New("Unable to generate subscription id")
// idGenerator helper utility that generates a (pseudo) random sequence of
// bytes that are used to generate identifiers.
func idGenerator() *rand.Rand {
if seed, err := binary.ReadVarint(bufio.NewReader(crand.Reader)); err == nil {
return rand.New(rand.NewSource(seed))
}
return "0x" + hex.EncodeToString(subid[:]), nil
return rand.New(rand.NewSource(int64(time.Now().Nanosecond())))
}
// NewID generates a identifier that can be used as an identifier in the RPC interface.
// e.g. filter and subscription identifier.
func NewID() ID {
subscriptionIDGenMu.Lock()
defer subscriptionIDGenMu.Unlock()
id := make([]byte, 16)
for i := 0; i < len(id); i += 7 {
val := subscriptionIDGen.Int63()
for j := 0; i+j < len(id) && j < 7; j++ {
id[i+j] = byte(val)
val >>= 8
}
}
return ID("0x" + hex.EncodeToString(id))
}