chatlab

Overview ¶

Package chatlab is ChatLab, a chat service: rooms, message history over HTTP and live messages over WebSocket with fan-out to every member. It is the reference app for the chat pack.

Planted bottlenecks (see README.md), each switched off by a fix flag:

• fanout: a message is written to every member in turn while the room lock is held, so delivery time grows with the room's size and one slow reader stalls the room (fix "fanout" queues per connection and drops readers that fall too far behind).
• history: the room log is never trimmed, and a history request encodes the whole log to return its tail, so history gets slower with every message ever sent (fix "history" keeps the last 200).
• presence: each join and leave sends the full member list to every member, so a reconnect storm costs the square of the room's size (fix "presence" sends only who joined or left and the count).