cmd/anubis: implement health check (#685)

Closes #681

Signed-off-by: Xe Iaso <me@xeiaso.net>

2 files changed, 26 insertions, 0 deletions

diff --git a/Earthfile b/Earthfile
index 740d0ec..65529b4 100644
--- a/Earthfile
+++ b/Earthfile
@@ -72,6 +72,8 @@ anubis-amd64:
     CMD ["/app/bin/anubis"]
     USER 1000:1000
 
+    HEALTHCHECK --interval=30s --timeout=5s --start-period=5s --retries=3 CMD ["/app/bin/anubis", "--healthcheck"]
+
     SAVE IMAGE --push ghcr.io/xe/x/anubis:latest
 
 anubis-arm64:
@@ -79,6 +81,8 @@ anubis-arm64:
     CMD ["/app/bin/anubis"]
     USER 1000:1000
 
+    HEALTHCHECK --interval=30s --timeout=5s --start-period=5s --retries=3 CMD ["/app/bin/anubis", "--healthcheck"]
+
     SAVE IMAGE --push ghcr.io/xe/x/anubis:latest
 
 anubis:
diff --git a/cmd/anubis/main.go b/cmd/anubis/main.go
index 9b39aab..69be826 100644
--- a/cmd/anubis/main.go
+++ b/cmd/anubis/main.go
@@ -42,6 +42,7 @@ var (
 	robotsTxt           = flag.Bool("serve-robots-txt", false, "serve a robots.txt file that disallows all robots")
 	policyFname         = flag.String("policy-fname", "", "full path to anubis policy document (defaults to a sensible built-in policy)")
 	target              = flag.String("target", "http://localhost:3923", "target to reverse proxy to")
+	healthcheck         = flag.Bool("healthcheck", false, "run a health check against Anubis")
 
 	//go:embed static botPolicies.json
 	static embed.FS
@@ -84,9 +85,30 @@ const (
 //go:generate zstd -f -k --ultra -22 static/js/main.mjs
 //go:generate brotli -fZk static/js/main.mjs
 
+func doHealthCheck() error {
+	resp, err := http.Get("http://localhost" + *metricsBind + "/metrics")
+	if err != nil {
+		return fmt.Errorf("failed to fetch metrics: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+
+	return nil
+}
+
 func main() {
 	internal.HandleStartup()
 
+	if *healthcheck {
+		if err := doHealthCheck(); err != nil {
+			log.Fatal(err)
+		}
+		return
+	}
+
 	s, err := New(*target, *policyFname)
 	if err != nil {
 		log.Fatal(err)