> It can't know exactly where the connection died, which means that the client must inform the last time it received an update, and the server must then crawl b

> It can't know exactly where the connection died, which means that the client must inform the last time it received an update, and the server must then crawl back a log to find the pending messages and redispatch them. I don't see how this is meaningfully different for long polling. The client could have received some updates but never ack'd it successfully over a long poll, so either way you need to keep a log and resync on reconnection.