mirror of https://github.com/coredns/coredns.git synced 2026-07-12 10:40:10 -04:00

Files

Nikolaus Schuetz af1e34ebc8 test: poll instead of fixed sleeps across several tests (#8275 )

Several tests slept a fixed duration then took a single snapshot of an
async result, racing whatever they waited on:
- forward health tests waited 20ms for the health-check goroutine to bump
  an atomic counter,
- the auto plugin tests (dns + metrics) waited 50-110ms for a file-watch
  reload to be picked up,
- the file ZoneReload test waited 30ms (self-described as could still be
  racy) for a reload,
- the overloaded health test slept 1s for its background goroutine to fire
  its first request.

Replace each with a bounded poll of the actual condition (the atomic
counter, a dns.Exchange response, a metrics scrape, z.ApexIfDefined, or a
channel signalled by the test's own handler) so they pass as soon as the
awaited state is reached and no longer flake when it is slower than the
fixed wait. Test-only.

Signed-off-by: Nikolaus Schuetz <nikolauspschuetz@gmail.com>

2026-07-10 15:20:57 -07:00

health_test.go

Use http constants instead of string (#5908 )

2023-02-09 12:29:49 +01:00

health.go

lint(revive): fix unused-parameter violations (#7980 )

2026-03-29 17:02:20 -07:00

log_test.go

Clean up tests logging (#1979 )

2018-07-19 16:23:06 +01:00

overloaded_test.go

test: poll instead of fixed sleeps across several tests (#8275 )

2026-07-10 15:20:57 -07:00

overloaded.go

Enable Prometheus native histograms (#6524 )

2024-03-11 16:09:09 -04:00

README.md

plugin/health: Bypass proxy in self health check (#5401 )

2022-06-17 15:49:53 -04:00

setup_test.go

fix: use descriptive error for unknown block options in health and log plugins (#8128 )

2026-05-27 16:29:24 -07:00

setup.go

fix: use descriptive error for unknown block options in health and log plugins (#8128 )

2026-05-27 16:29:24 -07:00

README.md

health

Name

health - enables a health check endpoint.

Description

Enabled process wide health endpoint. When CoreDNS is up and running this returns a 200 OK HTTP status code. The health is exported, by default, on port 8080/health.

Syntax

health [ADDRESS]

Optionally takes an address; the default is :8080. The health path is fixed to /health. The health endpoint returns a 200 response code and the word "OK" when this server is healthy.

An extra option can be set with this extended syntax:

health [ADDRESS] {
    lameduck DURATION
}

Where lameduck will delay shutdown for DURATION. /health will still answer 200 OK. Note: The ready plugin will not answer OK while CoreDNS is in lame duck mode prior to shutdown.

If you have multiple Server Blocks, health can only be enabled in one of them (as it is process wide). If you really need multiple endpoints, you must run health endpoints on different ports:

com {
    whoami
    health :8080
}

net {
    erratic
    health :8081
}

Doing this is supported but both endpoints ":8080" and ":8081" will export the exact same health.

Metrics

If monitoring is enabled (via the prometheus plugin) then the following metrics are exported:

coredns_health_request_duration_seconds{} - The health plugin performs a self health check once per second on the /health endpoint. This metric is the duration to process that request. As this is a local operation it should be fast. A (large) increase in this duration indicates the CoreDNS process is having trouble keeping up with its query load.
coredns_health_request_failures_total{} - The number of times the self health check failed.

Note that these metrics do not have a server label, because being overloaded is a symptom of the running process, not a specific server.

Examples

Run another health endpoint on http://localhost:8091.

. {
    health localhost:8091
}

Set a lame duck duration of 1 second:

. {
    health localhost:8092 {
        lameduck 1s
    }
}