Issue #65: prometheus dynamic config

dockerfiles/prometheus/Dockerfile

@@ -1,5 +1,7 @@
 FROM prom/prometheus:latest
+COPY prometheus.yml.tmpl /etc/prometheus/prometheus.yml.tmpl
+COPY entrypoint.sh /entrypoint.sh
 
-COPY prometheus.yaml /etc/prometheus/prometheus.yml
+ENV ENABLE_BACKEND_METRICS=false
 
-CMD ["--config.file=/etc/prometheus/prometheus.yml", "--web.enable-remote-write-receiver"]
+ENTRYPOINT ["/entrypoint.sh"]

dockerfiles/prometheus/entrypoint.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+if [ "$ENABLE_BACKEND_METRICS" = "true" ]; then
+  BACKEND_JOB="- job_name: 'backend'\n    metrics_path: '/metrics'\n    static_configs:\n      - targets: ['backend:5000']"
+else
+  BACKEND_JOB=""
+fi
+
+# Replace placeholder in the template
+sed "s|{{BACKEND_JOB}}|$BACKEND_JOB|" /etc/prometheus/prometheus.yml.tmpl > /etc/prometheus/prometheus.yml
+
+# Start Prometheus
+exec /bin/prometheus --config.file=/etc/prometheus/prometheus.yml --web.enable-remote-write-receiver

dockerfiles/prometheus/prometheus.yaml → dockerfiles/prometheus/prometheus.yml.tmpl

@@ -7,7 +7,4 @@ scrape_configs:
     static_configs:
       - targets: ['localhost:9090']
 
-  - job_name: 'backend'
-    metrics_path: '/metrics'
-    static_configs:
-      - targets: ['backend:5000']
+  {{BACKEND_JOB}}