fix prom example and add test

Author: zeitlinger

.github/workflows/prometheus-test.yml

@@ -0,0 +1,27 @@
+name: OATS Tests
+
+on:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - .github/workflows/prometheus-test.yml
+      - mise.toml
+      - .mise/tasks/prometheus-test.sh
+      - 'prometheus/**'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  acceptance-tests:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Check out
+        uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
+
+      - uses: jdx/mise-action@9dc7d5dd454262207dea3ab5a06a3df6afc8ff26 # v3.4.1
+
+      - name: Run Prometheus test
+        run: mise run prometheus-test

.mise/tasks/prometheus-test.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+#MISE description="Run Prometheus example build"
+
+set -euo pipefail
+
+cd prometheus
+../gradlew shadowJar
+# start docker compose in background
+docker compose start
+
+# check that 200 is returned from the metrics endpoint
+curl -f localhost:19090/metrics > /dev/null 2>&1 || (echo "Metrics endpoint did not return 200" && exit 1)
+# check that 200 is returned from the Prometheus server
+curl -f http://localhost:9090 > /dev/null 2>&1 || (echo "Prometheus did not return 200" && exit 1)
+
+echo "Prometheus example build and endpoints are working correctly"
+
+docker compose down

prometheus/README.md

@@ -32,14 +32,18 @@ docker compose up
 
 ## 3 - View Metrics
 
-To view metrics in Prometheus, navigate to:
+To view metrics in Prometheus (e.g. 90% percentile), navigate to:
 
-http://localhost:9090/graph?g0.range_input=15m&g0.expr=incoming_messages&g0.tab=0
+http://localhost:9090/query?g0.expr=histogram_quantile%28.90%2C+sum+by%28le%29+%28rate%28super_timer_milliseconds_bucket%5B5m%5D%29%29%29&g0.show_tree=0&g0.tab=graph&g0.range_input=15m&g0.res_type=auto&g0.res_density=medium&g0.display_mode=lines&g0.show_exemplars=0
 
 To fetch application metrics in prometheus format, run:
-
+ 
+```shell
 curl localhost:19090/metrics
+```
 
 To fetch application metrics in OpenMetrics format, which includes exemplars, run:
 
+```shell
 curl -H 'Accept: application/openmetrics-text; version=1.0.0; charset=utf-8' localhost:19090/metrics
+```

prometheus/prometheus.yml

@@ -8,7 +8,7 @@ alerting:
     - targets: []
     scheme: http
     timeout: 10s
-    api_version: v1
+    api_version: v2
 scrape_configs:
 - job_name: prometheus
   honor_timestamps: true