[Question] Channel presence

[michalzaq12]

Question about channel presence

Is there any situation in which I need to explicitly re-enter client presence? I’m not using the recover feature — just the default options. I’m particularly curious about the case when Ably reconnects with a fallback host (Error code: 80023 — Unable to resume connection from a different site). The documentation doesn’t explicitly state whether an explicit presence re-entry is required for error 80023 (or other cases where the connection fails to resume).

┆Issue is synchronized with this Jira Task by Unito

[paddybyers]

If calling code enters presence, the library will attempt to ensure at all times that that member is re-entered following disconnection (whether reconnection is continuous or not). The relevant behaviour in the spec is in https://sdk.ably.com/builds/ably/specification/main/features/#RTP17.

The only circumstances in which the client would no longer attempt to reenter (other than an explicit leave() by the calling code) are:

• if the channel becomes detached - this could be a result of client action, or in some circumstances (some internal server error or problem) there can be a server-initiated detach;
• if the channel is failed - this would be for example if the client no longer has rights for that channel.
  (See https://sdk.ably.com/builds/ably/specification/main/features/#RTP5a.)

The other possibility is that the client attempts to reenter but this fails; for example if the presence limit for the channel has been reached while the client was disconnected. If this happens, an update event will be emitted on the channel, with the reason. From this point forward the client will no longer automatically attempt to reenter. The calling code might elect to retry at a later time. See https://sdk.ably.com/builds/ably/specification/main/features/#RTP17e.