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dendrite/syncapi/sync/userstream.go
Kegsay 5e9dce1c0c
syncapi: Rename and split out tokens (#1025)
* syncapi: Rename and split out tokens

Previously we used the badly named `PaginationToken` which was
used for both `/sync` and `/messages` requests. This quickly
became confusing because named fields like `PDUPosition` meant
different things depending on the token type. Instead, we now have
two token types: `TopologyToken` and `StreamingToken`, both of
which have fields which make more sense for their specific situations.

Updated the codebase to use one or the other. `PaginationToken` still
lives on as `syncToken`, an unexported type which both tokens rely on.
This allows us to guarantee that the specific mappings of positions
to a string remain solely under the control of the `types` package.
This enables us to move high-level conceptual things like
"decrement this topological token" to function calls e.g
`TopologicalToken.Decrement()`.

Currently broken because `/messages` seemingly used both stream and
topological tokens, though I need to confirm this.

* final tweaks/hacks

* spurious logging

* Review comments and linting
2020-05-13 12:14:50 +01:00

160 lines
4.4 KiB
Go

// Copyright 2017 Vector Creations Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package sync
import (
"context"
"runtime"
"sync"
"time"
"github.com/matrix-org/dendrite/syncapi/types"
)
// UserStream represents a communication mechanism between the /sync request goroutine
// and the underlying sync server goroutines.
// Goroutines can get a UserStreamListener to wait for updates, and can Broadcast()
// updates.
type UserStream struct {
UserID string
// The lock that protects changes to this struct
lock sync.Mutex
// Closed when there is an update.
signalChannel chan struct{}
// The last sync position that there may have been an update for the user
pos types.StreamingToken
// The last time when we had some listeners waiting
timeOfLastChannel time.Time
// The number of listeners waiting
numWaiting uint
}
// UserStreamListener allows a sync request to wait for updates for a user.
type UserStreamListener struct {
userStream *UserStream
// Whether the stream has been closed
hasClosed bool
}
// NewUserStream creates a new user stream
func NewUserStream(userID string, currPos types.StreamingToken) *UserStream {
return &UserStream{
UserID: userID,
timeOfLastChannel: time.Now(),
pos: currPos,
signalChannel: make(chan struct{}),
}
}
// GetListener returns UserStreamListener that a sync request can use to wait
// for new updates with.
// UserStreamListener must be closed
func (s *UserStream) GetListener(ctx context.Context) UserStreamListener {
s.lock.Lock()
defer s.lock.Unlock()
s.numWaiting++ // We decrement when UserStreamListener is closed
listener := UserStreamListener{
userStream: s,
}
// Lets be a bit paranoid here and check that Close() is being called
runtime.SetFinalizer(&listener, func(l *UserStreamListener) {
if !l.hasClosed {
l.Close()
}
})
return listener
}
// Broadcast a new sync position for this user.
func (s *UserStream) Broadcast(pos types.StreamingToken) {
s.lock.Lock()
defer s.lock.Unlock()
s.pos = pos
close(s.signalChannel)
s.signalChannel = make(chan struct{})
}
// NumWaiting returns the number of goroutines waiting for waiting for updates.
// Used for metrics and testing.
func (s *UserStream) NumWaiting() uint {
s.lock.Lock()
defer s.lock.Unlock()
return s.numWaiting
}
// TimeOfLastNonEmpty returns the last time that the number of waiting listeners
// was non-empty, may be time.Now() if number of waiting listeners is currently
// non-empty.
func (s *UserStream) TimeOfLastNonEmpty() time.Time {
s.lock.Lock()
defer s.lock.Unlock()
if s.numWaiting > 0 {
return time.Now()
}
return s.timeOfLastChannel
}
// GetSyncPosition returns last sync position which the UserStream was
// notified about
func (s *UserStreamListener) GetSyncPosition() types.StreamingToken {
s.userStream.lock.Lock()
defer s.userStream.lock.Unlock()
return s.userStream.pos
}
// GetNotifyChannel returns a channel that is closed when there may be an
// update for the user.
// sincePos specifies from which point we want to be notified about. If there
// has already been an update after sincePos we'll return a closed channel
// immediately.
func (s *UserStreamListener) GetNotifyChannel(sincePos types.StreamingToken) <-chan struct{} {
s.userStream.lock.Lock()
defer s.userStream.lock.Unlock()
if s.userStream.pos.IsAfter(sincePos) {
// If the listener is behind, i.e. missed a potential update, then we
// want them to wake up immediately. We do this by returning a new
// closed stream, which returns immediately when selected.
closedChannel := make(chan struct{})
close(closedChannel)
return closedChannel
}
return s.userStream.signalChannel
}
// Close cleans up resources used
func (s *UserStreamListener) Close() {
s.userStream.lock.Lock()
defer s.userStream.lock.Unlock()
if !s.hasClosed {
s.userStream.numWaiting--
s.userStream.timeOfLastChannel = time.Now()
}
s.hasClosed = true
}