Iodine limits and settings

I will, at some point, document these... here's the key points:

SSL/TLS

  • TLS support requires OpenSSL 1.1.0 and above. On Heroku, this requires heroku-18.

  • Iodine supports TLS 1.2 and above (depending on the OpenSSL version used).

HTTP limits

  • Uploads are adjustable and limited to ~50Mib by default.

  • HTTP connection timeout (keep-alive) is adjustable and set to ~60 seconds by default.

  • HTTP total header size is adjustable and limited to ~32Kib by default.

  • HTTP header line length size is limited to a hard-coded limit of 8Kb.

  • HTTP headers count is limited to a hard-coded limit of 128 headers.

Websocket

  • Incoming Websocket message size limits are adjustable and limited to ~250Kib by default.

EventSource / SSE

  • Iodine will automatically attempt to send a ping event instead of disconnecting the connection. The ping interval is the same as the HTTP connection timeout interval.

Pub/Sub

  • Channel names are binary safe and unlimited in length. However, name lengths effect performance.

    **Do NOT allow clients to dictate the channel name**, as they might use extremely long names and cause resource starvation.

  • Pub/sub is limited to the process cluster. To use pub/sub with an external service (such as Redis) an "Engine" is required (see YARD documentation).

  • Pub/sub pattern matching supports only the Redis pattern matching approach. This makes patterns significantly more expensive and exact matches simpler and faster.

    It's recommended to prefer exact channel/stream name matching when possible.