Documentation

Everything a check can express, in one page.

Probe types

Type	What it does	Default timeout
http	GET or POST, follows redirects unless disabled	5s
tcp	Connect only, measures handshake time	3s
tls	Handshake plus certificate inspection	5s
dns	Resolves a name, optionally asserts the answer	2s

Expectations

A check passes when every expectation holds. An empty expect block means "any response at all counts as up", which is rarely what you want.

expect:
  status: 200            # exact code, or a range like 2xx
  body_contains: "ok"    # substring, case sensitive
  header:
    content-type: application/json
  max_latency: 800ms     # fail if slower, even on 200

Intervals and flapping

State changes only after threshold consecutive results agree. The default is 2, which removes most single-packet noise without adding a meaningful delay to real outages.

interval: 60s
timeout: 5s
threshold: 2
regions: [eu-central, eu-west]

Notifications

• webhook — POST with a JSON body describing the transition.
• email — one message per transition, no batching.
• silent — record only, useful while tuning a new check.

Webhook payload

{
  "check": "api-health",
  "from": "up",
  "to": "down",
  "at": "2026-02-14T09:31:02Z",
  "reason": "status 503, expected 200",
  "latency_ms": 1841
}

Certificate warnings

For tls and https probes the certificate is inspected on every run. A warning fires once per day inside the window, and the check itself only fails when the certificate is actually invalid — not when it is merely close to expiry.

tls:
  warn_before: 21d
  require_chain: true

Limits

Response bodies are read up to 256 KiB and discarded after matching. Redirect chains stop at 10 hops. A single check may target one host; use separate checks for separate hosts so their history stays separate.