Add GET /metrics endpoint with Prometheus output

KrisSimon · claude · KrisSimon · commit ff4905bd9243 · 2026-02-21T22:54:21.000+01:00
Co-Authored-By: Claude Sonnet 4.6 &lt;noreply@anthropic.com&gt;
diff --git a/api.aro b/api.aro
@@ -1,43 +1,47 @@
 (* HTTP Route Handlers *)
 
 (serveStatic: StatusPost API) {
-    <Extract> the <file> from the <pathParameters: file>.
-    <Create> the <template-path> with "static/" ++ <file>.
-    <Transform> the <content> from the <template: template-path>.
-    <Return> an <OK: status> with <content>.
+    Extract the <file> from the <pathParameters: file>.
+    Create the <template-path> with "static/" ++ <file>.
+    Transform the <content> from the <template: template-path>.
+    Return an <OK: status> with <content>.
 }
 
 (homePage: StatusPost API) {
-    <Retrieve> the <all-messages> from the <message-repository>.
-    <Extract> the <recent-messages: 0-19> from the <all-messages>.
-    <Transform> the <html> from the <template: index.html>.
-    <Return> an <OK: status> with <html>.
+    Retrieve the <all-messages> from the <message-repository>.
+    Extract the <recent-messages: 0-19> from the <all-messages>.
+    Transform the <html> from the <template: index.html>.
+    Return an <OK: status> with <html>.
 }
 
 (getMessages: StatusPost API) {
-    <Retrieve> the <all-messages> from the <message-repository>.
-    <Extract> the <recent-messages: 0-19> from the <all-messages>.
-    <Return> an <OK: status> with <recent-messages>.
+    Retrieve the <all-messages> from the <message-repository>.
+    Extract the <recent-messages: 0-19> from the <all-messages>.
+    Return an <OK: status> with <recent-messages>.
 }
 
 (postMessage: StatusPost API) {
-    <Extract> the <body> from the <request: body>.
-    <Extract> the <message-text: message> from the <body>.
-    <Create> the <message: Message> with {
+    Extract the <body> from the <request: body>.
+    Extract the <message-text: message> from the <body>.
+    Create the <message: Message> with {
         message: <message-text>,
         createdAt: <now>
     }.
-    <Store> the <message> into the <message-repository>.
-    <Broadcast> the <message> to the <websocket>.
-    <Return> a <Created: status> with <message>.
+    Store the <message> into the <message-repository>.
+    Broadcast the <message> to the <websocket>.
+    Return a <Created: status> with <message>.
+}
+
+(getMetrics: StatusPost API) {
+    Return an <OK: status> with <metrics: prometheus>.
 }
 
 (* Repository Observer - cleanup when message count exceeds 40 *)
 (Cleanup Messages: message-repository Observer) when <message-repository: count> > 40 {
-    <Retrieve> the <all-messages> from the <message-repository>.
-    <Extract> the <keep-messages: 0-19> from the <all-messages>.
-    <Clear> the <all> from the <message-repository>.
-    <Store> the <keep-messages> into the <message-repository>.
-    <Log> "Cleaned up messages, kept last 20" to the <console>.
-    <Return> an <OK: status> for the <cleanup>.
+    Retrieve the <all-messages> from the <message-repository>.
+    Extract the <keep-messages: 0-19> from the <all-messages>.
+    Clear the <all> from the <message-repository>.
+    Store the <keep-messages> into the <message-repository>.
+    Log "Cleaned up messages, kept last 20" to the <console>.
+    Return an <OK: status> for the <cleanup>.
 }
diff --git a/openapi.yaml b/openapi.yaml
@@ -72,6 +72,18 @@ paths:
               schema:
                 $ref: '#/components/schemas/Message'
 
+  /metrics:
+    get:
+      operationId: getMetrics
+      summary: Prometheus metrics
+      responses:
+        '200':
+          description: ARO runtime metrics in Prometheus text exposition format
+          content:
+            text/plain:
+              schema:
+                type: string
+
 components:
   schemas:
     Message:
