probe.tcp

TCP probing checks whether a TCP port on a host is reachable by attempting a TCP connect and recording connect success and timing.

Arguments

You can use the following arguments with probe.tcp:

Name	Type	Description	Default	Required
scrape_interval	duration	Interval at which targets should be probed.	1m	no
targets	list(object)	List of TCP targets to probe. See target arguments below.		no
target_from	reference	Reference to a discovery configuration to load targets from.		no
forward_to	list(reference)	List of exporter references to send metrics to.		yes

Target Arguments

The TCP target object expects the following fields:

Name	Type	Description	Default	Required
target	string	A target string in the form host:port, ip:port or fqdn:port. The probe will attempt a TCP connect to this endpoint.		yes
timeout_sec	integer	Timeout in seconds for the TCP connect attempt.	15	no
labels	map(string)	Labels to attach to this target.		no

Notes:

• The target value must include a port. Targets without a port will fail the connect attempt (tests cover this edge case).
• You can use hostnames (e.g. localhost:1234) or FQDNs — they will be resolved before connecting. Use .invalid domains in tests for guaranteed DNS failures.

Example

Plain text configuration

probe "tcp" "service_tcp" {
	scrape_interval = "30s"
	targets = [
		{
			target = "10.0.0.5:80"
			timeout_sec = 5
			labels = {
				service = "backend"
				env = "staging"
			}
		}
	]

	forward_to = [exporter.otlp.otlp]
}

Hostname (FQDN) example

probe "tcp" "local_check" {
	targets = [
		{ target = "localhost:8080" }
	]
	forward_to = [exporter.prometheus.prom]
}

From discovery (file)

discovery "file" "tcp_targets" {
	path = ["./targets/tcp.json"]
}

probe "tcp" "discovered" {
	target_from = discovery.file.tcp_targets
	forward_to = [exporter.otlp.otlp]
}

Resources

None yet.