feat: enable Prometheus exporter

.changeset/fair-games-rule.md

@@ -0,0 +1,5 @@
+---
+"varnish-post": minor
+---
+
+Enable Prometheus Exporter by setting `ENABLE_PROMETHEUS_EXPORTER` to `true`.

Dockerfile

@@ -1,3 +1,16 @@
+# Build the prometheus_varnish_exporter binary
+FROM docker.io/library/golang:1.22 as prometheus_varnish_exporter
+WORKDIR /app
+
+# Releases: https://github.com/jonnenauha/prometheus_varnish_exporter/releases
+ARG PROMETHEUS_VARNISH_EXPORTER_VERSION=1.6.1
+
+RUN git clone https://github.com/jonnenauha/prometheus_varnish_exporter.git . \
+  && git checkout "${PROMETHEUS_VARNISH_EXPORTER_VERSION}" \
+  && go mod download \
+  && go build -o prometheus_varnish_exporter
+
+# Build the final image
 FROM docker.io/library/ubuntu:22.04
 
 # Configuration
@@ -11,6 +24,7 @@ ENV DISABLE_ERROR_CACHING="true"
 ENV DISABLE_ERROR_CACHING_TTL="30s"
 ENV CONFIG_FILE="default.vcl"
 ENV ENABLE_LOGS="true"
+ENV ENABLE_PROMETHEUS_EXPORTER="false"
 
 # Install some dependencies
 RUN apt-get update \
@@ -21,11 +35,16 @@ RUN apt-get update \
   varnish-modules \
   && apt-get clean
 
+# Get the prometheus_varnish_exporter binary
+COPY --from=prometheus_varnish_exporter \
+  /app/prometheus_varnish_exporter \
+  /usr/local/bin/prometheus_varnish_exporter
+
 # Deploy our custom configuration
 WORKDIR /etc/varnish
 COPY config/ /templates
 COPY entrypoint.sh /
 RUN chmod +x /entrypoint.sh
 
-EXPOSE 80 8443
+EXPOSE 80 8443 9131
 ENTRYPOINT [ "tini", "--", "/entrypoint.sh" ]

README.md

@@ -27,6 +27,8 @@ You can use following environment variables for configuration:
 - `DISABLE_ERROR_CACHING_TTL`: time where requests should be directly sent to the backend after an error occured (default: `30s`)
 - `CONFIG_FILE`: the name of the configuration file to use (default: `default.vcl`)
 - `ENABLE_LOGS`: enable logs (default: `true`)
+- `ENABLE_PROMETHEUS_EXPORTER`: enable the Prometheus exporter if set to `true` (default: `false`).
+  If enabled, the exporter will be available on the 9131 port.
 
 ## Cache invalidation
 

entrypoint.sh

@@ -1,6 +1,7 @@
 #!/bin/sh
 
 ENABLE_LOGS="${ENABLE_LOGS}"
+ENABLE_PROMETHEUS_EXPORTER="${ENABLE_PROMETHEUS_EXPORTER}"
 
 set -eu
 
@@ -18,6 +19,13 @@ if [ "${ENABLE_LOGS}" = "true" ]; then
   varnishncsa&
 fi
 
+# Start prometheus_varnish_exporter if enabled
+if [ "${ENABLE_PROMETHEUS_EXPORTER}" = "true" ]; then
+  (sleep 2 && prometheus_varnish_exporter \
+    -web.listen-address ":9131" \
+    -web.telemetry-path "/metrics") &
+fi
+
 set -x
 
 # Run Varnish