socket.io does not wait for adapter to indicate that it is ready

[bytenik]

You want to:

• report a bug
• request a feature

Current behaviour

socket.io instantiates the specified adapter, but does not wait for a callback that it is ready. This works fine for many scenarios, but not one where the adapter needs to spool up long-running processes where the adapter is not ready to do work until they are completed. Connections from clients are handled immediately, and if you use a simple pattern of emit-on-connect from client, an early client can easily connect prior to adapter readiness.

Expected behaviour

socket.io should pass a callback to the adapter constructor and wait for it to be called prior to continuing to stand up.

Other information (e.g. stacktraces, related issues, suggestions how to fix)

This is particularly critical for the adapter I am developing that works with AWS SQS/SNS -- https://github.com/thinkalpha/socket.io-sqs