github.com/centrifugal/centrifuge

• Add Node.Survey method – it allows gathering results from all running nodes. It's possible to define your own survey handlers. See example. Keep in mind that Survey does not scale very well as number of Centrifuge Nodes grows. Though it has reasonably good performance to perform rare tasks even with relatively large number of nodes – see benchmark in pull request
• The main motivation of adding Node.Survey was attempt to remove Broker.Channels method – which is not supported by most of existing PUB/SUB brokers and does not work in Redis cluster. Broker.Channels now removed, but it can be replaced with survey if needed
• Improve clustering - node will now send a SHUTDOWN message so other nodes have a chance to realize that node left cluster almost immediately
• Signature of Since history call option changed – it now accepts a pointer to StreamPosition. This change simplifies a code to construct history call
• Added SubscribeOptions.Position boolean flag to enable positioning in channel stream. Positioning means that Centrifuge will check that the client did not miss any message from PUB/SUB system, as soon as loss detected client will be disconnected with Insufficient State reason. This is very similar to what Recover: true option did, but Position: true does not enable recovery. As soon as Position flag enabled Centrifuge will expose top stream StreamPosition information to a client in Subscribe Reply
• Added possibility to iterate over a channel history stream from client side. See an example that demonstrates this
• New Config options: HistoryMaxPublicationLimit and RecoveryMaxPublicationLimit to control maximum number of publications to return during history call or recovery process. See Centrifuge documentation for detailed description
• New example that shows Centrifuge integration with Tarantool. Tarantool engine implementation can outperform Redis (up to 5-10x for presence and history operations), though while example contains a full-featured fast Engine implementation – it's still just an example at the moment and have not been tested in production environment
• New blog post in Centrifugo blog where we introduce Centrifuge library
• Most examples now do not use jQuery which was replaced by vanilla JS

$ gorelease -base v0.14.2 -version v0.15.0
github.com/centrifugal/centrifuge
---------------------------------
Incompatible changes:
- (*MemoryEngine).Channels: removed
- (*MemoryEngine).PublishControl: changed from func([]byte) error to func([]byte, string) error
- (*Node).Channels: removed
- (*RedisEngine).Channels: removed
- (*RedisEngine).PublishControl: changed from func([]byte) error to func([]byte, string) error
- Broker.Channels, method set of Engine: removed
- Broker.Channels: removed
- Broker.PublishControl: changed from func([]byte) error to func([]byte, string) error
- BrokerEventHandler.HandlePublication: changed from func(string, *Publication) error to func(string, *Publication, StreamPosition) error
- Since: changed from func(StreamPosition) HistoryOption to func(*StreamPosition) HistoryOption
Compatible changes:
- (*Node).ID: added
- (*Node).OnSurvey: added
- (*Node).Survey: added
- Config.HistoryMaxPublicationLimit: added
- Config.RecoveryMaxPublicationLimit: added
- ErrorUnrecoverablePosition: added
- HistoryEvent.Filter: added
- SubscribeOptions.Position: added
- SurveyCallback: added
- SurveyEvent: added
- SurveyHandler: added
- SurveyReply: added
- SurveyResult: added

v0.15.0 is a valid semantic version for this release.

• fix concurrent map access which could result in runtime crash when using presence feature.

• remove unused history_full metric, add history action metric to track all history calls.

• Add possibility to disconnect user with custom Disconnect object, and with client ID whitelist.
• Thus fixing non-working WithReconnect option when calling node.Disconnect method.
• No error returned from client.Disconnect method anymore. It was always nil before.

Here is what changed since v0.13.0:

gorelease -base v0.13.0 -version v0.14.0
github.com/centrifugal/centrifuge
---------------------------------
Incompatible changes:
- (*Client).Disconnect: changed from func(*Disconnect) error to func(*Disconnect)
- DisconnectOptions.Reconnect: removed
- DisconnectOptions: old is comparable, new is not
- WithReconnect: removed
Compatible changes:
- DisconnectOptions.ClientWhitelist: added
- DisconnectOptions.Disconnect: added
- WithClientWhitelist: added
- WithDisconnect: added

v0.14.0 is a valid semantic version for this release.

This release solves two important issues from v1.0.0 library milestone. It has API changes, though as always it's possible to implement the same as before, and adapting new version should be pretty straightforward.

• #163 Provide a way to add concurrent processing of protocol commands. Before this change protocol commands could only be processed one by one. The obvious drawback in this case is that one slow RPC could result into stopping other requests from being processed thus affecting overall latency. This required changing client handler API and use asynchronous callback style API for returning replies from event handlers. This approach while not being very idiomatic allows using whatever concurrency strategy developer wants without losing the possibility to control event order.
• #161 Eliminating ChannelOptionsFunc – now all channel options can be provided when calling Publish operation (history size and TTL) or by returning from event handlers inside SubscribeReply (enabling channel presence, join/leave messages, recovery in a channel). This means that channel options can now be controlled per-connection (not only per channel as before). For example if you need admin connection to subscribe to channel but not participate in channel presence – you are able to not enable presence for that connection.
• Server-side subscriptions now set over Subscriptions map (instead of Channels). Again – subscribe options can be set with per-connection resolution.
• Change signature of Publish method in Broker interface – method now accepts []byte data instead of *Publication.
• Function options for Unsubbscribe and Disconnect methods now have boolean argument.
• History functional option WithNoLimit removed – use WithLimit(centrifuge.NoLimit) instead.
• Config option ClientUserConnectionLimit renamed to UserConnectionLimit. If UserConnectionLimit set then now connection will be disconnected with DisconnectConnectionLimit instead of returning a LimitExceeded error.

Since API changes are pretty big, let's look at example program and how to adapt it from v0.12.0 to v0.13.0.

The program based on v0.12.0 API:

package main

import (
	"context"

	"github.com/centrifugal/centrifuge"
)

func main() {
	cfg := centrifuge.DefaultConfig
	cfg.ChannelOptionsFunc = func(channel string) (centrifuge.ChannelOptions, bool, error) {
		return centrifuge.ChannelOptions{
			Presence:        true,
			JoinLeave:       true,
			HistorySize:     100,
			HistoryLifetime: 300,
			HistoryRecover:  true,
		}, true, nil
	}

	node, _ := centrifuge.New(cfg)

	node.OnConnecting(func(ctx context.Context, e centrifuge.ConnectEvent) (centrifuge.ConnectReply, error) {
		return centrifuge.ConnectReply{
			Credentials: &centrifuge.Credentials{UserID: "42"},
			// Subscribe to a server-side channel.
			Channels: []string{"news"},
		}, nil
	})

	node.OnConnect(func(c *centrifuge.Client) {
		println("client connected")
	})

	node.OnSubscribe(func(c *centrifuge.Client, e centrifuge.SubscribeEvent) (centrifuge.SubscribeReply, error) {
		return centrifuge.SubscribeReply{}, nil
	})

	node.OnPublish(func(c *centrifuge.Client, e centrifuge.PublishEvent) (centrifuge.PublishReply, error) {
		return centrifuge.PublishReply{}, nil
	})

	node.OnDisconnect(func(c *centrifuge.Client, e centrifuge.DisconnectEvent) {
		println("client disconnected")
	})

	_ = node.Run()
}

With v0.13.0 the same program becomes:

package main

import (
	"context"
	"time"

	"github.com/centrifugal/centrifuge"
)

func main() {
	node, _ := centrifuge.New(centrifuge.DefaultConfig)

	node.OnConnecting(func(ctx context.Context, e centrifuge.ConnectEvent) (centrifuge.ConnectReply, error) {
		return centrifuge.ConnectReply{
			Credentials: &centrifuge.Credentials{UserID: "42"},
			// Subscribe to a server-side channel.
			Subscriptions: map[string]centrifuge.SubscribeOptions{
				"news": {Presence: true, JoinLeave: true, Recover: true},
			},
		}, nil
	})

	node.OnConnect(func(client *centrifuge.Client) {
		println("client connected")

		client.OnSubscribe(func(e centrifuge.SubscribeEvent, cb centrifuge.SubscribeCallback) {
			cb(centrifuge.SubscribeReply{
				Options: centrifuge.SubscribeOptions{
					Presence:  true,
					JoinLeave: true,
					Recover:   true,
				},
			}, nil)
		})

		client.OnPublish(func(e centrifuge.PublishEvent, cb centrifuge.PublishCallback) {
			// BTW you can publish here explicitly using node.Publish method – see Result
			// field of PublishReply and chat_json example.
			cb(centrifuge.PublishReply{
				Options: centrifuge.PublishOptions{
					HistorySize: 100,
					HistoryTTL:  5 * time.Minute,
				},
			}, nil)
		})

		client.OnDisconnect(func(e centrifuge.DisconnectEvent) {
			println("client disconnected")
		})
	})

	_ = node.Run()
}

As you can see there are three important changes:

1. You should now set up event handlers inside node.OnConnect closure
2. Event handlers now have callback argument that you should call with corresponding Reply as soon as you have it
3. For server-side subscriptions you should now return Subscriptions field in ConnectReply which is map[string]SubscribeOptions instead of []string slice.

See new example that demonstrates concurrency using bounded semaphore.

Note that every feature enabled for a channel increases resource usage on a server. You should only enable presence, recovery, join/leave features and maintaining history in channels where this is necessary.

See also updated Tips and tricks section in a README – it now contains information about connection life cycle and event handler concurrency.

This release is a step back in Engine separation and has some important fixes and improvements. Backwards incompatible changes are all about Engine interfaces so if you are using built-in Memory or Redis engines you should be fine to upgrade. Otherwise, take a closer look on first and second points below.

• HistoryManager interface removed and its methods now part of Broker interface{}. The reason behind this is that Broker should be responsible for an atomicity of saving message into history stream and publish to PUB/SUB. More details in #158
• Cleaner Broker interface methods without ChannelOptions
• Fix reconnects due to InsufficientState errors in channels with HistoryRecover option on when using Memory Engine and frequently publishing in parallel (from different goroutines)
• Fix reconnects due to InsufficientState errors when using legacy seq, gen fields - #157
• Fix returning custom disconnect for SockJS transport
• Possibility to define history stream options in Publish call
• Deprecate Broker/Engine Channels method – see #147
• Increase test coverage up to 83% so #106 is finally closed
• Test Sentinel scenario in CI
• Refactor queue writer to prevent possible message loss on connection close - 160
• Fix inconsistent tests of Redis Cluster recovery due to PUB/SUB buffering
• Minor improvements in Gin auth example - #154

I have a plan for future library versions to remove ChannelOptionFunc completely (but still have a control over channel feature set). This is still in research – if you are interested welcome to #161.

$ gorelease -base v0.11.2 -version v0.12.0
github.com/centrifugal/centrifuge
---------------------------------
Incompatible changes:
- (*MemoryEngine).AddHistory: removed
- (*MemoryEngine).Publish: changed from func(string, *Publication, *ChannelOptions) error to func(string, *Publication, PublishOptions) (StreamPosition, error)
- (*MemoryEngine).PublishJoin: changed from func(string, *ClientInfo, *ChannelOptions) error to func(string, *ClientInfo) error
- (*MemoryEngine).PublishLeave: changed from func(string, *ClientInfo, *ChannelOptions) error to func(string, *ClientInfo) error
- (*Node).SetHistoryManager: removed
- (*RedisEngine).AddHistory: removed
- (*RedisEngine).Publish: changed from func(string, *Publication, *ChannelOptions) error to func(string, *Publication, PublishOptions) (StreamPosition, error)
- (*RedisEngine).PublishJoin: changed from func(string, *ClientInfo, *ChannelOptions) error to func(string, *ClientInfo) error
- (*RedisEngine).PublishLeave: changed from func(string, *ClientInfo, *ChannelOptions) error to func(string, *ClientInfo) error
- Broker.History: added
- Broker.Publish: changed from func(string, *Publication, *ChannelOptions) error to func(string, *Publication, PublishOptions) (StreamPosition, error)
- Broker.PublishJoin: changed from func(string, *ClientInfo, *ChannelOptions) error to func(string, *ClientInfo) error
- Broker.PublishLeave: changed from func(string, *ClientInfo, *ChannelOptions) error to func(string, *ClientInfo) error
- Broker.RemoveHistory: added
- HistoryManager.AddHistory, method set of Engine: removed
- HistoryManager: removed
- MemoryEngine: old is comparable, new is not
- PublishOptions.SkipHistory: removed
- RedisEngineConfig.PublishOnHistoryAdd: removed
Compatible changes:
- PublishOptions.HistorySize: added
- PublishOptions.HistoryTTL: added
- WithHistory: added

v0.12.0 is a valid semantic version for this release.

• Fix non-working websocket close with custom disconnect code: this is a regression introduced by v0.11.0.

• Added MetricsNamespace field of Config to configure Prometheus metrics namespace used by Centrifuge library internal metrics
• Fix messages_sent_counter – it now correctly counts Control, Join and Leave messages
• Redis cluster integration now tested in CI

$ gorelease -base v0.11.0 -version v0.11.1
github.com/centrifugal/centrifuge
---------------------------------
Compatible changes:
- Config.MetricsNamespace: added

v0.11.1 is a valid semantic version for this release.