Added prometheus and grafana services to docker compose (#21213)

ref
https://linear.app/tryghost/issue/ENG-1591/add-prometheus-and-grafana-services-to-docker-compose

This commit adds 2 new services to the docker compose file to enable
monitoring metrics from Ghost locally in real-time:
1. Prometheus - a service that scrapes Ghost's new `/metrics` endpoint
introduced in this
[commit](768336efad).
2. Grafana - a service that consumes the metrics from prometheus and
exposes them in a dashboard that you can view locally at
`localhost:3000`.

# Usage
Both of these services are selectively enabled using docker compose
[profiles](https://docs.docker.com/compose/how-tos/profiles/). This way,
if you don't opt-in to using these monitoring tools, they won't start
and consume resources on your host machine. To enable these services,
enable the `monitoring` profile by either setting the `COMPOSE_PROFILES`
environment variable to `monitoring`, or specifying the `--profile
monitoring` CLI argument to any `docker compose ...` commands.

I've found the easiest way to configure this in an 'always on' fashion
is to create a `.env` file in the project's root directory and add
`COMPOSE_PROFILES=monitoring` to it. As an added convenience, you can
also set `COMPOSE_FILE=.github/scripts/docker-compose.yml`, which will
allow you to run `docker compose ...` commands from the root directory
without specifying the full path each time.

# Intended for development only
These services are meant for local development only, and are not
configured for a production use-case. For example, the Grafana instance
is configured to have _no authorization_ so you won't need a
username/password to login at `localhost:3000`. Prometheus is also
configured to scrape the metrics once every second, which is likely
excessive for production use-cases, but may be useful for getting more
granular metrics while e.g. load testing locally.

# Dashboards
The Grafana instance includes a default dashboard including most of the
main default metrics provided by our prometheus client integration. The
dashboard is defined in a JSON file at
`.github/scripts/docker/grafana/dashboards/main-dashboard.json' and can
be modified & committed to add new visualizations that will be available
to anyone work on Ghost locally. You can also add other dashboards to
the same directory for specific use-cases, which should be picked up and
made available in the Grafana UI. [Read
more](https://grafana.com/docs/grafana/latest/dashboards/build-dashboards/view-dashboard-json-model/)
about Grafana's JSON schema for dashboards.

.github/scripts/docker-compose.yml

@@ -28,5 +28,27 @@ services:
     ports:
       - "6379:6379"
     restart: always
+  prometheus:
+    profiles: [monitoring]
+    image: prom/prometheus:v2.30.3
+    container_name: ghost-prometheus
+    ports:
+      - "9090:9090"
+    restart: always
+    volumes:
+      - ./prometheus/prometheus.yml:/etc/prometheus/prometheus.yml
+  grafana:
+    profiles: [monitoring]
+    image: grafana/grafana:8.2.3
+    container_name: ghost-grafana
+    ports:
+      - "3000:3000"
+    restart: always
+    environment:
+      - GF_AUTH_ANONYMOUS_ENABLED=true
+    volumes:
+      - ./grafana/datasources:/etc/grafana/provisioning/datasources
+      - ./grafana/dashboard.yml:/etc/grafana/provisioning/dashboards/main.yaml
+      - ./grafana/dashboards:/var/lib/grafana/dashboards
 volumes:
   mysql-data:

.github/scripts/grafana/dashboard.yml

@@ -0,0 +1,15 @@
+## This file is used to point to the folder where the dashboards are stored
+## To edit or create a dashboard, add a .json file to the ./dashboards folder
+
+apiVersion: 1
+
+providers:
+  - name: "Dashboard provider"
+    orgId: 1
+    type: file
+    disableDeletion: false
+    updateIntervalSeconds: 10
+    allowUiUpdates: false
+    options:
+      path: /var/lib/grafana/dashboards
+      foldersFromFilesStructure: true

.github/scripts/grafana/datasources/datasource.yml

@@ -0,0 +1,9 @@
+apiVersion: 1
+
+datasources:
+- name: Prometheus
+  type: prometheus
+  url: http://prometheus:9090
+  isDefault: true
+  access: proxy
+  editable: true

.github/scripts/prometheus/prometheus.yml

@@ -0,0 +1,31 @@
+global:
+  scrape_interval:     15s # By default, scrape targets every 15 seconds.
+
+  # Attach these labels to any time series or alerts when communicating with
+  # external systems (federation, remote storage, Alertmanager).
+  external_labels:
+    monitor: 'codelab-monitor'
+
+# A scrape configuration containing exactly one endpoint to scrape:
+# Here it's Prometheus itself.
+scrape_configs:
+  # The job name is added as a label `job=<job_name>` to any timeseries scraped from this config.
+  - job_name: 'prometheus'
+
+    # Override the global default and scrape targets from this job every 5 seconds.
+    scrape_interval: 5s
+
+    static_configs:
+      - targets: ['localhost:9090']
+
+  - job_name: 'ghost'
+
+    scrape_interval: 1s
+
+    static_configs:
+      - targets: ['host.docker.internal:9416']
+
+    metrics_path: '/metrics'
+
+remote_write:
+  - url: http://grafana:3000/api/prom/push