---
slug: pubsub
title: Redis Managed Pub/Sub Server
---

The Pub/Sub engine powering
[Redis ServerEvents](/redis-server-events) and [Redis MQ](/redis-mq) has been extracted
and encapsulated it into a re-usable class that can be used independently for handling messages
published to specific [Redis Pub/Sub](http://redis.io/commands#pubsub) channels.

`RedisPubSubServer` processes messages in a managed background thread that **automatically reconnects**
when the redis-server connection fails and works like an independent background Service that can be
stopped and started on command.

## API

The public API is captured in the [IRedisPubSubServer](https://github.com/ServiceStack/ServiceStack/blob/master/src/ServiceStack.Interfaces/Redis/IRedisPubSubServer.cs) interface:

```csharp
public interface IRedisPubSubServer : IDisposable
{
    IRedisClientsManager ClientsManager { get; }
    // What Channels it's subscribed to
    string[] Channels { get; }

    // Run once on initial StartUp
    Action OnInit { get; set; }
    // Called each time a new Connection is Started
    Action OnStart { get; set; }
    // Invoked when Connection is broken or Stopped
    Action OnStop { get; set; }
    // Invoked after Dispose()
    Action OnDispose { get; set; }

    // Fired when each message is received
    Action<string, string> OnMessage { get; set; }
    // Fired after successfully subscribing to the specified channels
    Action<string> OnUnSubscribe { get; set; }
    // Called when an exception occurs 
    Action<Exception> OnError { get; set; }
    // Called before attempting to Failover to a new redis master
    Action<IRedisPubSubServer> OnFailover { get; set; }

    int? KeepAliveRetryAfterMs { get; set; }
    // The Current Time for RedisServer
    DateTime CurrentServerTime { get; }

    // Current Status: Starting, Started, Stopping, Stopped, Disposed
    string GetStatus();
    // Different life-cycle stats
    string GetStatsDescription();
    
    // Subscribe to specified Channels and listening for new messages
    IRedisPubSubServer Start();
    // Close active Connection and stop running background thread
    void Stop();
    // Stop than Start
    void Restart();
}
```

## Usage

To use `RedisPubSubServer`, initialize it with the channels you want to subscribe to and assign handlers
for each of the events you want to handle. At a minimum you'll want to handle `OnMessage`:

```csharp
var clientsManager = new PooledRedisClientManager();
var redisPubSub = new RedisPubSubServer(clientsManager, "channel-1", "channel-2") {
        OnMessage = (channel, msg) => "Received '{0}' from '{1}'".Print(msg, channel)
    }.Start();
```

Calling `Start()` after it's initialized will get it to start listening and processing any messages
published to the subscribed channels.