fix prom example and add test (open-telemetry#909)

Co-authored-by: Jay DeLuca <jaydeluca4@gmail.com>
Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>

Author: 3 people

.github/scripts/prometheus-test.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+cd prometheus
+../gradlew shadowJar
+docker compose up -d
+
+function ready() {
+  # 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)
+}
+
+# wait up to 2 minutes for the endpoints to be ready
+timeout=120
+interval=5
+elapsed=0
+while ! ready; do
+  if [ $elapsed -ge $timeout ]; then
+    echo "Timeout waiting for Prometheus endpoints to be ready"
+    docker compose logs
+    docker compose down
+    exit 1
+  fi
+  echo "Waiting for Prometheus endpoints to be ready..."
+  sleep $interval
+  elapsed=$((elapsed + interval))
+done
+
+echo "Prometheus example build and endpoints are working correctly"
+
+docker compose down

.github/workflows/prometheus-test.yml

@@ -0,0 +1,35 @@
+name: Prometheus Test
+
+on:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - .github/workflows/prometheus-test.yml
+      - .github/scripts/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
+
+      - name: Set up JDK for running Gradle
+        uses: actions/setup-java@dded0888837ed1f317902acf8a20df0ad188d165 # v5.0.0
+        with:
+          distribution: temurin
+          java-version: 17
+
+      - name: Set up gradle
+        uses: gradle/actions/setup-gradle@4d9f0ba0025fe599b4ebab900eb7f3a1d93ef4c2 # v5.0.0
+        with:
+          cache-read-only: ${{ github.event_name == 'pull_request' }}
+
+      - name: Run Prometheus test
+        run: .github/scripts/prometheus-test.sh

prometheus/Dockerfile

@@ -2,4 +2,4 @@ FROM eclipse-temurin:11.0.29_7-jre@sha256:5a9b558567e6a2f7fbaa5000891caf515c31db
 
 ADD build/libs/opentelemetry-examples-prometheus-*-SNAPSHOT-all.jar /app.jar
 
-ENTRYPOINT java -cp app.jar io.opentelemetry.example.prometheus.PrometheusExample 19090
+ENTRYPOINT exec java -cp app.jar io.opentelemetry.example.prometheus.PrometheusExample 19090

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. 90th 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/docker-compose.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   app:
     build: ./

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