Add /health endpoint for watch

Author: prymitive

.github/spellcheck/wordlist.txt

@@ -30,6 +30,7 @@ humanize
 io
 JSON
 linter
+liveness
 matcher
 matchers
 md

cmd/pint/watch.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io"
 	"log/slog"
 	"net/http"
 	_ "net/http/pprof"
@@ -180,6 +181,9 @@ func actionWatch(c *cli.Context, meta actionMeta, f pathFinderFunc) error {
 	rulesParsedTotal.WithLabelValues(config.RecordingRuleType).Add(0)
 	rulesParsedTotal.WithLabelValues(config.InvalidRuleType).Add(0)
 
+	http.HandleFunc("/health", func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = io.WriteString(w, "OK\n")
+	})
 	http.Handle("/metrics", promhttp.HandlerFor(metricsRegistry, promhttp.HandlerOpts{
 		ErrorLog: slog.NewLogLogger(slog.Default().Handler(), slog.LevelError),
 		Timeout:  time.Second * 20,

docs/changelog.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## v0.70.0
+
+### Added
+
+- When running `pint watch` command `/health` HTTP endpoint can now be used for liveness probes.
+
 ## v0.69.1
 
 ### Fixed

docs/index.md

@@ -152,6 +152,15 @@ Run pint as a daemon in watch mode where it continuously checks
 all rules found in selected files and exposes metrics about
 found problems.
 
+By default it will start a HTTP server on port `8080` and run all checks every
+10 minutes. This can be customised by passing extra flags to the `watch` command.
+Run `pint watch -h` to see all available flags.
+
+Currently supported HTTP paths:
+
+- `/health` - static endpoint for liveness probes.
+- `/metrics` - returns Prometheus metrics, see below.
+
 #### Manually selecting files and directories
 
 You can tell it to continuously test specific files or directories:
@@ -203,11 +212,7 @@ pint watch rule_files local
 
 #### Accessing watch mode metrics
 
-By default it will start a HTTP server on port `8080` and run all checks every
-10 minutes. This can be customised by passing extra flags to the `watch` command.
-Run `pint watch -h` to see all available flags.
-
-Query `/metrics` to see all expose metrics, example with default flags:
+Query `/metrics` HTTP endpoint to see all expose metrics, example with default flags:
 
 ```shell
 curl -s http://localhost:8080/metrics