Cent

======

No backwards incompatible changes here.

Improvements:

* New section in docs – Centrifugo dev blog, check out [first post about scaling WebSocket](https://centrifugal.github.io/centrifugo/blog/scaling_websocket/)
* Possibility to [scale with Nats server](https://centrifugal.github.io/centrifugo/server/engines/#nats-broker) for **unreliable at most once PUB/SUB**
* Subscribe HTTP proxy, [see docs](https://centrifugal.github.io/centrifugo/server/proxy/#subscribe-proxy)
* Publish HTTP proxy, [see docs](https://centrifugal.github.io/centrifugo/server/proxy/#publish-proxy)
* Support for setting Redis Sentinel password, [see in docs](https://centrifugal.github.io/centrifugo/server/engines/#redis-sentinel-for-high-availability)
* Various documentation improvements since previous release

This release based on massively updated [Centrifuge](https://github.com/centrifugal/centrifuge) library, we don't expect problems but since many things were refactored – we suggest to carefully test your app.

======

No backwards incompatible changes here.

Improvements:

* refreshed [documentation design](https://centrifugal.github.io/centrifugo/)
* new [Quick start](https://centrifugal.github.io/centrifugo/quick_start/) chapter for those who just start working with Centrifugo
* faster marshal of disconnect messages into close frame texts, significantly reduces amount of memory allocations during server graceful shutdown in deployments with many connections
* one beautiful Centrifugo integration with Symfony framework from our community - [check it out](https://github.com/fre5h/CentrifugoBundle)

Fixes:

* add `Content-Type: application/json` header to outgoing HTTP proxy requests to app backend for better integration with some frameworks. [368](https://github.com/centrifugal/centrifugo/issues/368)
* fix wrong channel name in Join messages sent to client in case of server-side subscription to many channels
* fix disconnect code unmarshalling after receiving response from HTTP proxy requests, it was ignored previously

======

No backwards incompatible changes here.

Starting from this release we begin migration to new `offset` `uint64` client-server protocol field for Publication position inside history stream instead of currently used `seq` and `gen` (both `uint32`) fields. This `offset` field will be used in Centrifugo v3 by default. This change required to simplify working with history API, and due to this change history API can be later extended with pagination features.

Our client libraries `centrifuge-js`, `centrifuge-go` and `centrifuge-mobile` were updated to support `offset` field. If you are using these libraries then you can update `centrifuge-js` to at least `2.6.0`, `centrifuge-go` to at least `0.5.0` and `centrifuge-mobile` to at least `0.5.0` to work with the newest client-server protocol. As soon as you upgraded mentioned libraries you can enable `offset` support without waiting for Centrifugo v3 release with `v3_use_offset` option:

json
{
"v3_use_offset": true
}


All other client libraries except `centrifuge-js`, `centrifuge-go` and `centrifuge-mobile` do not support recovery at this moment and will only work with `offset` field in the future.

It's important to mention that `centrifuge-js`, `centrifuge-go` and `centrifuge-mobile` will continue to work with a server which is using `seq` and `gen` fields for recovery until Centrifugo v3 release. With Centrifugo v3 release those libraries will be updated to only work with `offset` field.

Command `centrifugo genconfig` will now generate config file with `v3_use_offset` option enabled. Documentation has been updated to suggest turning on this option for fresh installations.

Improvements:

* support [Redis Streams](https://redis.io/topics/streams-intro) - radically reduces amount of memory allocations during recovery in large history streams. This also opens a road to paginate over history stream in future releases, see description of new `redis_streams` option [in Redis engine docs](https://centrifugal.github.io/centrifugo/server/engines/#redis-streams)
* support [Redis Cluster](https://redis.io/topics/cluster-tutorial), client-side sharding between different Redis Clusters also works, see more [in docs](https://centrifugal.github.io/centrifugo/server/engines/#redis-cluster)
* faster HMAC-based JWT parsing
* faster Memory engine, possibility to expire history stream metadata (more [in docs](https://centrifugal.github.io/centrifugo/server/engines/#memory-engine))
* releases for Centos 8, Debian Buster, Ubuntu Focal Fossa
* new cli-command `centrifugo gentoken` to quickly generate HMAC SHA256 based connection JWT, [see docs](https://centrifugal.github.io/centrifugo/server/configuration/#gentoken-command)
* new cli-command `centrifugo checktoken` to quickly validate connection JWT while developing application, [see docs](https://centrifugal.github.io/centrifugo/server/configuration/#checktoken-command)

Fixes:

* fix server side subscriptions to private channels (were ignored before)
* fix `channels` counter update frequency in server `info` – this includes how fast `channels` counter updated in admin web interface (previously `num clients` and `num users` updated once in 3 seconds while `num channels` only once in a minute, now `num channels` updated once in 3 seconds too)

This release based on Go 1.14.x

======

This release is a step towards new interesting possibilities with Centrifugo. It adds server-side subscriptions support and some sugar on top of it. With server-side subscriptions you don't need to call `Subscribe` method on client side at all. Follow release notes to know more.

No backwards incompatible changes here.

Improvements:

* Server-side subscriptions, this functionality requires updating client code so at moment usage is limited to `centrifuge-js`. Also there is a possibility to automatically subscribe user connection to personal notifications channel. More info in [new documentation chapter](https://centrifugal.github.io/centrifugo/server/server_subs/)
* New private subscription JWT `eto` claim - see [its description in docs](https://centrifugal.github.io/centrifugo/server/private_channels/#eto)
* Options to disable WebSocket, SockJS and API handlers – [see docs](https://centrifugal.github.io/centrifugo/server/configuration/#disable-default-endpoints)
* New option `websocket_use_write_buffer_pool` – [see docs](https://centrifugal.github.io/centrifugo/transports/websocket/)
* Metrics now include histograms of requests durations - [pull request](https://github.com/centrifugal/centrifugo/pull/337)
* Add Linux ARM binary release

Fixes:

* Fix unreliable unsubscriptions from Redis PUB/SUB channels under load, now we unsubscribe nodes from PUB/SUB channels over in-memory queue
* Fix `tls_external` option regression

======

This release contains several improvements to proxy feature introduced in v2.3.0, no backwards incompatible changes here.

Improvements:

* With `proxy_extra_http_headers` configuration option it's now possible to set a list of extra headers that should be copied from original client request to proxied HTTP request - see [334](https://github.com/centrifugal/centrifugo/issues/334) for motivation and [updated proxy docs](https://centrifugal.github.io/centrifugo/server/proxy/)
* You can pass custom data in response to connect event and this data will be available in `connect` event callback context on client side. See [332](https://github.com/centrifugal/centrifugo/issues/332) for more details
* Starting from this release `Origin` header is proxied to your backend by default - see [full list in docs](https://centrifugal.github.io/centrifugo/server/proxy/#proxy-headers)

======

This release is a big shift in Centrifugo possibilities due to HTTP request proxy feature. It was a pretty long term work but the final result opens a new commucation direction: from client to server – see details below.

Release has some internal backwards incompatible changes in Redis engine and deprecations. **Migration must be smooth but we strongly suggest to test your functionality** before running new version in production. Read release notes below for more information.

Improvements:

* It's now possible to proxy some client connection events over HTTP to application backend and react to them in a way you need. For example you can authenticate connection via request from Centrifugo to your app backend, refresh client sessions and answer to RPC calls sent by client over WebSocket or SockJS connections. More information in [new documentation chapter](https://centrifugal.github.io/centrifugo/server/proxy/)
* Centrifugo now supports RSA-based JWT. You can enable this by setting `token_rsa_public_key` option. See [updated authentication chapter](https://centrifugal.github.io/centrifugo/server/authentication/) in docs for more details. Due to this addition we also renamed `secret` option to `token_hmac_secret_key` so it's much more meaningful in modern context. But don't worry - old `secret` option will work and continue to set token HMAC secret key until Centrifugo v3 release (which is not even planned yet). But we adjusted docs and `genconfig` command to use new naming
* New option `redis_sequence_ttl` for Redis engine. It allows to expire internal keys related to history sequnce meta data in Redis – current sequence number in channel and epoch value. See more motivation behind this option in [its description in Redis Engine docs](https://centrifugal.github.io/centrifugo/server/engines/#redis-engine). While adding this feature we changed how sequence and epoch values are stored in Redis - both are now fields of single Redis HASH key. This means that after updating to this version your clients won't recover missed messages - but your frontend application will receive `recovered: false` in subscription context so it should tolerate this loss gracefully recovering state from your main database (if everything done right on your client side of course)
* More validation of configuration file is now performed. Specifically we now check history recovery configuration - see [this issue](https://github.com/centrifugal/centrifuge-js/issues/99) to see how absence of such misconfiguration check resulted in confused Centrifugo behaviour - no messages were received by subscribers
* Go internal logs from HTTP server are now wrapped in our structured logging mechanism - those errors will look as warns in Centrifugo logs now
* Alpine 3.10 instead of Alpine 3.8 as Centrifugo docker image base