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Monitors

The six check types, targets, intervals, assertions, thresholds, and reading the results.

On this page
  1. Types
  2. Create a monitor
  3. Assertions (HTTP only)
  4. Thresholds
  5. Reading a monitor
  6. Pause and resume
  7. Limits
  8. API

A monitor runs one check on a schedule from our probes and keeps the result. Six kinds cover most of a stack; each has its own idea of a target and of what passing means.

Types

TypeTargetPasses when
HTTP(S)A URL starting with http:// or https://The response is 2xx or 3xx, or every assertion holds. Up to 5 redirects are followed; bodies are capped at 5 MB.
TCPhost:port, IPv6 as [addr]:portThe connection handshake completes within the timeout.
PingA hostname or IPAn ICMP echo reply arrives. If ICMP is blocked, a TCP connection or refusal on 443, 80 or 22 counts as reachable.
DNSA hostname (not an IP)The resolver returns at least one A, AAAA or CNAME record. NXDOMAIN and empty answers are failures with different messages.
SSL expiryA hostname, host:port or https:// URLThe certificate is trusted, matches the hostname and has not expired. Days left is recorded for reminders.
HeartbeatNone. We give you a URL your job pings.A ping arrived within one and a half intervals. See Heartbeat monitors.
Targets that resolve to private or internal addresses (10.x, 192.168.x, 127.x, link-local and so on) are refused at save time and again at check time. Monitors can only watch things reachable from the public internet.

Create a monitor

The New monitor drawer with type, name, target and interval
The New monitor drawer. Advanced holds assertions, timeout and thresholds.
  1. Pick the type and paste the target

    The target is checked as you save: a TCP monitor without a port, a DNS monitor given an IP address, or a hostname that resolves to a private range are rejected with a plain reason.

  2. Choose an interval

    From 30 seconds to 24 hours. The floor depends on your plan: 5 minutes on Free, 1 minute on Starter, 30 seconds on Team. Intervals below the floor are raised to it.

  3. Open Advanced when you need it

    Assertions, timeout, and the failure and recovery thresholds.

Assertions (HTTP only)

AssertionPasses when
Status codeThe response status equals the value exactly, for example 200.
Response timeThe whole request takes less than the value, in milliseconds.
Body containsThe response body includes the string, for example "status":"ok".

Without assertions any 2xx or 3xx passes. With a status code assertion, that code and only that code passes. Assertions combine with and: every one must hold.

Thresholds

Failure threshold is how many consecutive failed checks mark the monitor down; recovery threshold is how many consecutive passes mark it up again. Both default to 2 and go from 1 to 10. Two and two means a single dropped packet does not page anyone, and a single lucky response does not declare victory. A brand-new monitor is Pending until its first pass, which brings it up immediately.

Reading a monitor

A monitor's detail with uptime, latency chart, recent checks and rules
A monitor's detail: uptime over the last checks, latency, the check log and the rules below.

The detail shows uptime and average latency over the last 60 checks, a latency chart, and the check log with each result's time, region, latency and error text. Raw checks are kept for 30 days; daily rollups feed the status page's uptime strip beyond that.

Pause and resume

Pausing stops checks and shows the monitor as Paused; it no longer affects components. Resuming resets the counters and runs a check straight away. Pause a monitor before planned work on its target if it is not covered by a maintenance window.

Limits

Plans set the number of monitors per organisation (1 on Free, 15 on Starter, 50 on Team) and the fastest interval. Reaching the limit answers with an upgrade prompt.

API

Monitors are CRUD on /user/monitors, with /pause, /resume, /checks and PUT /user/monitors/:id/rules. See Monitors in the API reference.