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MySQL - Postgres Monitoring

Adding MySQL and PostgreSQL to the monitoring stack​

This guide extends the base monitoring stack (Prometheus + Grafana + Node Exporter) to include MySQL and PostgreSQL metrics. The approach follows the same exporter pattern — a dedicated exporter per database translates DB internals into Prometheus metrics.

Architecture overview​

mysql-container (:3306) -> mysql-exporter (:9104) -> Prometheus (:9090) -> Grafana (:3000)
instance-prostgress (:5432) -> postgres-exporter (:9187) ----------------------->|

Prerequisites​

  • The base monitoring stack is already running (Prometheus, Grafana, Node Exporter).
  • MySQL and PostgreSQL are running as Docker containers on the same server.
  • Both DB containers must be connected to the same Docker network as the monitoring stack.

Step 1 — Connect DB containers to the monitoring network​

Containers started outside of Docker Compose need to be manually added to the monitoring network.

Note: Docker Compose prefixes network names with the project folder name. If your stack lives in /root/monitoring, the network will be called monitoring_monitoring.

docker network connect monitoring_monitoring mysql-container
docker network connect monitoring_monitoring instance-prostgress

Verify they appear in the network:

docker network inspect monitoring_monitoring | grep Name

Step 2 — Create read-only exporter users​

Never use root or your application user for exporters. Create dedicated read-only users on each database.

MySQL:

docker exec mysql-container mysql -u root -pmypassword -e "CREATE USER 'exporter'@'%' IDENTIFIED BY 'exporter123'; GRANT PROCESS, REPLICATION CLIENT, SELECT ON *.* TO 'exporter'@'%'; FLUSH PRIVILEGES;"

PostgreSQL:

docker exec instance-prostgress psql -U postgres -c "CREATE USER exporter WITH PASSWORD 'exporter123'; GRANT pg_monitor TO exporter;"

Step 3 — Create the MySQL exporter config file​

Version 0.19.0 of mysqld-exporter requires credentials via a .my.cnf config file instead of environment variables.

mkdir -p /root/monitoring/mysql-exporter

Create /root/monitoring/mysql-exporter/.my.cnf with the following content:

[client]
user=exporter
password=exporter123
host=mysql-container
port=3306

Step 4 — Add exporters to docker-compose.yml​

Add both exporter services to your existing docker-compose.yml:

  mysql-exporter:
    image: prom/mysqld-exporter:latest
    container_name: mysql-exporter
    restart: always
    ports:
      - "9104:9104"
    volumes:
      - ./mysql-exporter/.my.cnf:/cfg/.my.cnf:ro
    command:
      - "--config.my-cnf=/cfg/.my.cnf"
      - "--collect.info_schema.innodb_metrics"
    networks:
      - monitoring

  postgres-exporter:
    image: prometheuscommunity/postgres-exporter:latest
    container_name: postgres-exporter
    restart: always
    ports:
      - "9187:9187"
    environment:
      - DATA_SOURCE_NAME=postgresql://exporter:exporter123@instance-prostgress:5432/postgres?sslmode=disable
    networks:
      - monitoring

Key decisions explained​

SettingWhy
.my.cnf mounted as :roVersion 0.19.0+ of mysqld-exporter dropped DATA_SOURCE_NAME support and requires a config file. The :ro flag prevents the container from modifying it.
--collect.info_schema.innodb_metricsEnables InnoDB metrics like buffer pool size, disabled by default but required by most Grafana dashboards.
sslmode=disableDisables SSL for internal Docker network connections where encryption is not needed.

Step 5 — Add scrape jobs to prometheus.yml​

  - job_name: 'mysql'
    static_configs:
      - targets: ['mysql-exporter:9104']

  - job_name: 'postgres'
    static_configs:
      - targets: ['postgres-exporter:9187']

Step 6 — Deploy and verify​

Bring up the new services and reload Prometheus:

cd /root/monitoring
docker compose up -d
docker compose restart prometheus

Check all exporters are running:

docker ps | grep exporter

Verify metrics are flowing in Prometheus by searching for mysql_up (should return 1) and pg_up (should return 1).

Step 7 — Import dashboards in Grafana​

Go to Dashboards → Import and use these community dashboard IDs:

DatabaseDashboard ID
MySQL7362
PostgreSQL9628

Select your Prometheus data source when prompted.

Troubleshooting​

Access denied for user 'exporter'

The exporter user password doesn't match what's in .my.cnf. Drop and recreate the user:

docker exec mysql-container mysql -u root -pmypassword -e "DROP USER 'exporter'@'%'; CREATE USER 'exporter'@'%' IDENTIFIED BY 'exporter123'; GRANT PROCESS, REPLICATION CLIENT, SELECT ON *.* TO 'exporter'@'%'; FLUSH PRIVILEGES;"

no configuration found in mysql-exporter logs

The .my.cnf file is not being picked up. Make sure the --config.my-cnf flag in the command block points to the correct mounted path:

command:
  - "--config.my-cnf=/cfg/.my.cnf"

Panel shows "No data" in Grafana

Some panels join MySQL and Node Exporter metrics using the instance label. If the instances don't match, the query returns nothing. Edit the panel and replace on (instance) with on () to remove the label matching requirement:

(mysql_global_variables_innodb_buffer_pool_size{instance="$host"} * 100) / on () node_memory_MemTotal_bytes

Target shows DOWN in Prometheus

Check that the DB container is on the monitoring network:

docker network inspect monitoring_monitoring | grep Name

If the container is missing, connect it manually:

docker network connect monitoring_monitoring mysql-container