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redis: configurable TCP keepalive and TCP_USER_TIMEOUT - #1285
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radix v4 hard-codes a 10s TCP keepalive on the connections it dials, and nothing sets TCP_USER_TIMEOUT. Keepalive probes are only sent on idle connections, so they cannot detect a dead peer while there is unacknowledged data in flight, which is exactly the state of a busy connection to a Redis server that vanished. The kernel then only closes it after net.ipv4.tcp_retries2 retransmissions, about 15 minutes by default. Add REDIS_TCP_USER_TIMEOUT / REDIS_PERSECOND_TCP_USER_TIMEOUT (Linux only, off by default) to bound how long sent data may stay unacknowledged, and REDIS_TCP_KEEPALIVE / REDIS_PERSECOND_TCP_KEEPALIVE (default 10s, as radix did; negative disables it). These complement the I/O timeout: TCP_USER_TIMEOUT catches a peer that stopped acknowledging, the I/O timeout catches one that acknowledges but never replies. golang.org/x/sys becomes a direct dependency. Also restore the "Connection Timeout" README intro, which envoyproxy#1272 reverted to "connection establishment" only while REDIS_TIMEOUT also bounds reads and writes since envoyproxy#1271. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: Ignasi Barrera <ignasi@tetrate.io>
psbrar99
approved these changes
Oct 22, 2026
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radix v4 hard-codes a 10s TCP keepalive on the connections it dials, and nothing sets TCP_USER_TIMEOUT. Keepalive probes are only sent on idle connections, so they cannot detect a dead peer while there is unacknowledged data in flight, which is exactly the state of a busy connection to a Redis server that vanished. The kernel then only closes it after net.ipv4.tcp_retries2 retransmissions, about 15 minutes by default.
Add REDIS_TCP_USER_TIMEOUT / REDIS_PERSECOND_TCP_USER_TIMEOUT (Linux only, off by default) to bound how long sent data may stay unacknowledged, and REDIS_TCP_KEEPALIVE / REDIS_PERSECOND_TCP_KEEPALIVE (default 10s, as radix did; negative disables it). These complement the I/O timeout: TCP_USER_TIMEOUT catches a peer that stopped acknowledging, the I/O timeout catches one that acknowledges but never replies.