Configure TCP probes

TCP probes are appropriate for non-HTTP services where reachability of a port is the signal: Redis, Postgres, RabbitMQ, internal RPC services. The agent opens a TCP connection, records the connect time in milliseconds, and closes the connection.

Configuration shape

{
  "host": "redis.internal",
  "port": 6379,
  "timeout_ms": 2000
}

Field reference

Field	Default	Notes
`host`	required	Hostname or IP.
`port`	required	Integer in `1..65535`.
`timeout_ms`	`2000`	Aborts the connection attempt when exceeded.

Reason codes

Reason	Meaning
`ETIMEDOUT`	Connection attempt did not complete within `timeout_ms`.
`ECONNREFUSED`	TCP connection refused.
`ENOTFOUND` / `EAI_AGAIN`	DNS resolution failed.
`tcp_error`	Other socket error. The exact code is logged on the agent.

Threshold examples

Goal	Healthy	Unhealthy
Reachable + fast handshake	`under 50`	`over 500`
Reachable	`under 1000`	`over 1500`

Pure reachability with no latency requirement: set unhealthy at timeout_ms - 1, leaving anything below as healthy.