From ab6622d6533c4f0b94fbcef138d3314d907303bc Mon Sep 17 00:00:00 2001
From: Lewis Buckley <lewis@37signals.com>
Date: Tue, 16 Sep 2025 11:16:02 +0100
Subject: [PATCH] Set up the OTel collector to gather and export metrics from
 containers

---
 config/deploy.yml         | 14 ++++++++++++
 config/otel_collector.yml | 45 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 config/otel_collector.yml

diff --git a/config/deploy.yml b/config/deploy.yml
index 19e9649ea..87c67950a 100644
--- a/config/deploy.yml
+++ b/config/deploy.yml
@@ -32,3 +32,17 @@ aliases:
   console: app exec -i --reuse "bin/rails console"
   ssh: app exec -i --reuse /bin/bash
   switch: accessory exec beamer --reuse "beamer switch --primary=<%= ENV["PRIMARY"] %>"
+
+accessories:
+  otel_collector:
+    image: otel/opentelemetry-collector-contrib:0.126.0
+    port: 9394
+    files:
+      - config/otel_collector.yml:/etc/otelcol-contrib/config.yaml
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+    options:
+      user: 0
+    roles:
+      - web
+      - jobs
diff --git a/config/otel_collector.yml b/config/otel_collector.yml
new file mode 100644
index 000000000..c66b0d297
--- /dev/null
+++ b/config/otel_collector.yml
@@ -0,0 +1,45 @@
+receivers:
+  prometheus:
+    config:
+      scrape_configs:
+        - job_name: "kamal-containers"
+          scrape_interval: 5s
+          docker_sd_configs:
+            - host: unix:///var/run/docker.sock
+              refresh_interval: 10s
+          relabel_configs:
+            # Limit scraping to labeled containers with port 9394 exposed
+            - source_labels: [__address__]
+              regex: .*:9394
+              action: keep
+            - source_labels: [__meta_docker_container_name]
+              regex: (/fizzy-(web|jobs)-.*|/kamal-proxy)
+              action: keep
+
+            # Pull service and role from Kamal Docker labels
+            - source_labels: [__meta_docker_container_label_service]
+              target_label: service
+            - source_labels: [__meta_docker_container_label_role]
+              target_label: role
+
+            - source_labels: [__meta_docker_container_name]
+              regex: ^/kamal-proxy$
+              target_label: service
+              replacement: kamal-proxy
+            - source_labels: [__meta_docker_container_name]
+              regex: ^/kamal-proxy$
+              target_label: role
+              replacement: proxy
+
+exporters:
+  prometheus:
+    endpoint: 0.0.0.0:9394
+
+service:
+  telemetry:
+    logs:
+      level: "warn"
+  pipelines:
+    metrics:
+      receivers: [prometheus]
+      exporters: [prometheus]