RTFM · Healthchecks
lb.saphira.redis: does it answer PING with PONG?
Redis's own health question, asked the honest way: the check says PING and demands PONG. If the server requires a password, the check authenticates first; from the environment, never echoed.
What it proves
A live Redis server on the RESP wire: optional AUTH (+OK required) and then PING → +PONG. A custom expect regex can pin the verdict further. Because PING exercises the command path (not just the socket), this catches the wedged-instance case where TCP connects but the event loop is stuck.
How it works
The probe engine speaks inline commands: AUTH with the password from LB_SAPHIRA_REDIS_PASSWORD when set (a non-+OK answer fails immediately), then PING, and matches the reply; +PONG by default, or your LB_SAPHIRA_EXPECT regex.
Configuration
| Variable | Default | Meaning |
|---|---|---|
| LB_SAPHIRA_REDIS_PASSWORD | - | AUTH password: env/conf only, never echoed |
| LB_SAPHIRA_EXPECT | - | Custom reply regex instead of +PONG |
| LB_SAPHIRA_TIMEOUT | 3 | Round-trip deadline |
| (target port) | $4, else 6379 | Any port redis-server listens on |
Wiring it up
# ldirectord.cf - cache pool
virtual = 203.0.113.10:6379
protocol = tcp
scheduler = lc
real = 192.168.20.111:6379 gate 1
real = 192.168.20.112:6379 gate 1
checktype = external
checkcommand = "/var/lib/lb/saphira/lb.saphira.redis"Run it by hand
LB_SAPHIRA_REDIS_PASSWORD=$(cat /etc/redis/hc-pass) \
/var/lib/lb/saphira/lb.saphira.redis cache-pool 6379 192.168.20.111 6379
echo $?
# 0 = (AUTH ok) + PONG
# 1 = AUTH refused, no PONG, or expect mismatchFailure modes
- NOAUTH/ERR on PING: the server requires a password the check was not given: configuration gap, exit path is 1 not silent
- Socket accepted, no PONG; event loop wedged (persistence fork stall is the classic): this check is the early warning
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