Add Dockerfile

.woodpecker.yml

@@ -0,0 +1,10 @@
+steps:
+  build:
+    image: "golang:1.21.5-alpine"
+    commands:
+      - go build main.go
+  lint:
+    image: "golang:1.21.5-alpine"
+    commands:
+      - go fmt ./main.go
+      - go vet ./main.go

Dockerfile

@@ -0,0 +1,9 @@
+FROM golang@sha256:fe5bea2e1ab3ffebe0267393fea88fcb197e2dbbb1e2dbabeec6dd9ccb0e1871 AS builder
+
+COPY . /build
+WORKDIR /build
+RUN go build -o cert-exporter main.go
+
+FROM alpine@sha256:beefdbd8a1da6d2915566fde36db9db0b524eb737fc57cd1367effd16dc0d06d
+COPY --from=builder /build/cert-exporter /opt/cert-exporter
+ENTRYPOINT ["/opt/cert-exporter"]

README.md

@@ -1,4 +1,23 @@
-# certs-status-exporter
+# cert-status-exporter
 
 A Prometheus exporter that checks the expiry and validity of configured domains
 once a day.
+
+## Usage
+
+To export certificate status metrics, run `cert-status-exporter --domain <domain>:<port>:<alpn>[:<name>]`.
+The format means: "Connect to `<domain>` on port `<port>` while advertising `<alpn>` as ALPN during the
+TLS negotiations. If `<name>` is specified, then the metric will be labeled as `<name>`, instead of `<domain>`.
+`<alpn>` is a semi-colon separated list of ALPN protocols.
+
+By default, `cert-status-exporter` will bind to `0.0.0.0:8888` and expose the metrics at `0.0.0.0:8888/metrics`. To change
+the binding address, you can specify `--host` and `--port` to change how `cert-status-exporter` binds the socket.
+
+### Example
+
+- `cert-status-exporter --host 127.0.0.1 --port 8383 --domain "gnu.org:443:http/1.1;http/1.0;http/0.9"`: Check the certificate of `gnu.org:443`, while presenting the HTTP ALPN protocol names during the TLS negotiation. The metrics are exported with the label `name` equal to `gnu.org`.
+- `cert-status-exporter --domain "example.org:5223:xmpp-client:xmpp"`: Check the certificate of `example.org:5223`, while presenting `xmpp-client` as the  ALPN protocol during the TLS negotiation. Moreover, export the certificate state with the label `name` equal to `xmpp`.
+
+## License
+
+See `LICENSE`.

main.go

@@ -166,17 +166,17 @@ func run(ctx *cli.Context) error {
 				updateMetrics(&metrics, lastUpdatedMetric)
 			},
 		),
+		gocron.WithStartAt(gocron.WithStartImmediately()),
 	)
 	if err != nil {
 		log.Error("Failed to create periodic task")
 		return err
 	}
 
-	// Perform an initial run to populate the metrics
+	// Start the scheduler
-	log.Info("Performing initial requests...")
+	scheduler.Start()
-	updateMetrics(&metrics, lastUpdatedMetric)
-	log.Debug("Done")
 
+	// Handle HTTP requests
 	http.Handle(
 		"/metrics", promhttp.HandlerFor(
 			registry,