Pusher Adapter

Ably enables migration from Pusher to Ably using its Pusher Adapter. The protocol adapter handles all background translation and only requires an API key change.

Using an adapter introduces some latency and is slower than using an Ably SDK, however the impact is typically in the low milliseconds. It will also be slightly slower than using Pusher natively, but only if you are close to whichever Pusher data center used. If you aren’t close to the Pusher data center you’ve chosen, then the extra latency from using the adapter should be more than compensated for by being able to use a data center that is close to you. This is because Ably automatically connects clients to the data center closest to them.

The Pusher Adapter provides some of the advantages of Ably, such as inter-regional message federation, however others, such as continuity guarantees, fallback host support, and message history are only available when using an Ably SDK. If an Ably SDK is available in your chosen platform, it is recommended you use that, or plan to transition to it eventually.

The following Pusher features are supported using the adapter:

• Realtime subscribe
• Realtime presence
• Realtime publish
• REST publish
• REST get occupied channels
• REST get presence set
• REST get user count

The Pusher protocol is not supported by default in Ably apps. This is due to security reasons associated with the use of public channels.

To enable the Pusher Adapter in an app:

1. Log into your Ably dashboard and create or select the app you’re using.
2. Click the Settings tab.
3. Check the box for Pusher protocol support under Protocol Adapter Settings.
4. Click Save settings.

Once you save the settings, you will be offered the choice for Ably to create a set of namespaces for you. These are required to provide interoperability with Pusher client libraries:

• Pusher public channels will use the public: namespace.
• Pusher private channels will use the private: namespace.
• Pusher presence channels will use the presence: namespace.

All namespaces must also have the Require identification channel rule disabled, as Pusher clients are never identified in the context of Ably. If you are receiving error code 40160 then Require identification is enabled.

Initialize your Pusher SDK to connect to Ably. All of Pusher’s SDKs are supported, and need to be configured similar to the following:

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const pusher = new Pusher('appId.keyId', {
  wsHost: 'realtime-pusher.ably.io',
  httpHost: 'realtime-pusher.ably.io',
  disableStats: true,
  forceTls: true,
  cluster: 'eu'
});

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You can also add any other Pusher options that you normally use.

Ably and Pusher have different naming restrictions for channel names, and use namespaces differently.

Channel names are mapped when using the adapter as follows:

• Pusher public channels will use the public: namespace.
• Pusher private channels will use the private: namespace.
• Pusher presence channels will use the presence: namespace.
• Channels not in any of the above namespaces were receive a private-ablyroot- prefix.

Colons are not permitted in Pusher channel names, but are used as namespace separators in Ably. Because of this, the adapter maps semicolons to colons in Ably channel names and colons to semicolons in Pusher channel names. This means that you will be unable to access any Ably channels with semicolons in their name.

The following are some example channel name mappings: