Add simple metrics endpoint for rageshake.

README.md

@@ -17,11 +17,17 @@ Optional parameters:
    [rageshake.sample.yaml](rageshake.sample.yaml) for more information.
  * `-listen <address>`: TCP network address to listen for HTTP requests
    on. Example: `:9110`.
+ * `-metrics <address>`: TCP network address to listen for HTTP requests
+   for prometheus metrics on. Example: `:9111`. Defaults to not being served.
 
 ## HTTP endpoints
 
 The following HTTP endpoints are exposed:
 
+### GET `/health`
+
+Returns a simple "ok" if the server is healthy, for use with automated healthchecks.
+
 ### GET `/api/listing/`
 
 Serves submitted bug reports. Protected by basic HTTP auth using the
@@ -100,6 +106,10 @@ The response (if successful) will be a JSON object with the following fields:
 * `report_url`: A URL where the user can track their bug report. Omitted if
   issue submission was disabled.
 
+### /metrics
+
+If the metrics address is configured with `-metrics` then prometheus metrics are visible here.
+
 ## Notifications
 
 You can get notifications when a new rageshake arrives on the server.

go.mod

@@ -5,7 +5,8 @@ go 1.16
 require (
 	github.com/google/go-github v0.0.0-20170401000335-12363ffc1001
 	github.com/jordan-wright/email v4.0.1-0.20200824153738-3f5bafa1cd84+incompatible
+	github.com/prometheus/client_golang v1.17.0 // indirect
 	github.com/xanzy/go-gitlab v0.50.2
-	golang.org/x/oauth2 v0.0.0-20181106182150-f42d05182288
-	gopkg.in/yaml.v2 v2.2.8
+	golang.org/x/oauth2 v0.8.0
+	gopkg.in/yaml.v2 v2.4.0
 )