smp: fix proxy reconnection to relay after restart#1806
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Reproduces the proxy failing to reconnect to a destination relay when the sender disconnects mid-connection (empty session var left in smpClients).
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Problem
An SMP proxy permanently stops reconnecting to a destination relay after the relay restarts. The logs show repeated
PCEResponseTimeoutfor that relay, and only restarting the proxy server recovers it.Cause
A
PRXYrequest makes the proxy open a connection to the relay in a worker forked from the sender's client. The worker inserts an empty session var intosmpClientsand then blocks in the connection/handshake. If the sender disconnects while that connect is in flight, the worker is killed by an async exception before the session var is ever filled.Nothing removes an empty session var, so every later request to that relay waits on it until the connection timeout and fails with
PROXY (BROKER TIMEOUT)- forever, even once the relay is healthy again.