Monitor MongoDB 8.0 performance with Prometheus and Grafana for real-time metrics and alerting

Install MongoDB Exporter for Prometheus

The MongoDB Exporter collects database metrics and exposes them in Prometheus format. Download and install the latest version.

wget https://github.com/percona/mongodb_exporter/releases/download/v0.40.0/mongodb_exporter-0.40.0.linux-amd64.tar.gz
tar -xzf mongodb_exporter-0.40.0.linux-amd64.tar.gz
sudo mv mongodb_exporter-0.40.0.linux-amd64/mongodb_exporter /usr/local/bin/
sudo chmod +x /usr/local/bin/mongodb_exporter

Create MongoDB monitoring user

Create a dedicated MongoDB user with minimal permissions for metrics collection. This user needs read access to database statistics and replica set status.

mongosh --host localhost:27017

use admin
db.createUser({
  user: "prometheus_monitor",
  pwd: "secure_monitoring_password_2024",
  roles: [
    { role: "read", db: "admin" },
    { role: "read", db: "local" },
    { role: "clusterMonitor", db: "admin" },
    { role: "readAnyDatabase", db: "admin" }
  ]
})
exit

Configure MongoDB Exporter service

Create a systemd service for the MongoDB Exporter with authentication credentials and collection settings.

[Unit]
Description=MongoDB Prometheus Exporter
After=network.target

[Service]
Type=simple
User=nobody
Group=nogroup
Environment=MONGODB_URI=mongodb://prometheus_monitor:secure_monitoring_password_2024@localhost:27017/admin
ExecStart=/usr/local/bin/mongodb_exporter --mongodb.uri=$MONGODB_URI --collect-all --web.listen-address=:9216
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target

Start and enable MongoDB Exporter

Enable the exporter service to start automatically and verify it's collecting metrics properly.

sudo systemctl daemon-reload
sudo systemctl enable --now mongodb-exporter
sudo systemctl status mongodb-exporter

Configure Prometheus to scrape MongoDB metrics

Add MongoDB Exporter as a scrape target in your Prometheus configuration. This assumes you have Prometheus installed and running.

global:
  scrape_interval: 15s
  evaluation_interval: 15s

rule_files:
  - "mongodb_alerts.yml"

scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

  - job_name: 'mongodb'
    static_configs:
      - targets: ['localhost:9216']
    scrape_interval: 30s
    metrics_path: /metrics

Create MongoDB alerting rules

Define alert conditions for MongoDB performance issues, connection problems, and replica set failures.

groups:
name: mongodb.rules
  rules:
  - alert: MongoDBDown
    expr: mongodb_up == 0
    for: 5m
    labels:
      severity: critical
    annotations:
      summary: "MongoDB instance is down"
      description: "MongoDB instance {{ $labels.instance }} has been down for more than 5 minutes."

  - alert: MongoDBHighConnections
    expr: mongodb_connections{state="current"} / mongodb_connections{state="available"} > 0.8
    for: 2m
    labels:
      severity: warning
    annotations:
      summary: "MongoDB connection usage high"
      description: "MongoDB instance {{ $labels.instance }} is using {{ $value | humanizePercentage }} of available connections."

  - alert: MongoDBSlowQueries
    expr: rate(mongodb_op_latencies_ops_total{type="command"}[5m]) > 100
    for: 2m
    labels:
      severity: warning
    annotations:
      summary: "MongoDB slow queries detected"
      description: "MongoDB instance {{ $labels.instance }} is experiencing {{ $value }} slow queries per second."

  - alert: MongoDBReplicaLag
    expr: mongodb_replset_member_replication_lag > 10
    for: 1m
    labels:
      severity: critical
    annotations:
      summary: "MongoDB replica lag high"
      description: "MongoDB replica {{ $labels.instance }} is lagging by {{ $value }} seconds."

  - alert: MongoDBHighMemoryUsage
    expr: mongodb_memory{type="resident"} / 1024 / 1024 > 4000
    for: 5m
    labels:
      severity: warning
    annotations:
      summary: "MongoDB high memory usage"
      description: "MongoDB instance {{ $labels.instance }} is using {{ $value }}MB of memory."

Restart Prometheus with new configuration

Reload Prometheus configuration to start collecting MongoDB metrics and enable alerting rules.

sudo systemctl restart prometheus
sudo systemctl status prometheus

Import MongoDB dashboard into Grafana

Create a comprehensive Grafana dashboard for MongoDB monitoring. First, access your Grafana instance and import a dashboard configuration.

curl -s https://raw.githubusercontent.com/percona/grafana-dashboards/main/dashboards/MongoDB_Overview.json > mongodb_dashboard.json

Configure custom MongoDB dashboard

Create a custom dashboard with key MongoDB performance panels. Log into Grafana and create a new dashboard with these essential panels.

{
  "dashboard": {
    "title": "MongoDB Performance",
    "panels": [
      {
        "title": "MongoDB Status",
        "type": "stat",
        "targets": [{
          "expr": "mongodb_up",
          "legendFormat": "MongoDB Up"
        }]
      },
      {
        "title": "Operations per Second",
        "type": "graph",
        "targets": [{
          "expr": "rate(mongodb_op_counters_total[5m])",
          "legendFormat": "{{ type }}"
        }]
      },
      {
        "title": "Connection Usage",
        "type": "graph",
        "targets": [{
          "expr": "mongodb_connections",
          "legendFormat": "{{ state }}"
        }]
      },
      {
        "title": "Memory Usage",
        "type": "graph",
        "targets": [{
          "expr": "mongodb_memory",
          "legendFormat": "{{ type }}"
        }]
      },
      {
        "title": "Query Execution Time",
        "type": "graph",
        "targets": [{
          "expr": "mongodb_op_latencies_latency_total / mongodb_op_latencies_ops_total",
          "legendFormat": "{{ type }}"
        }]
      }
    ]
  }
}

Configure Grafana alerts

Set up Grafana alerts that complement your Prometheus alerting rules. Configure notification channels for email or Slack integration.

curl -X POST http://localhost:3000/api/alert-notifications \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_GRAFANA_API_KEY" \
  -d '{
    "name": "mongodb-alerts",
    "type": "email",
    "settings": {
      "addresses": "admin@example.com",
      "subject": "MongoDB Alert: {{ .Title }}"
    }
  }'

Configure replica set monitoring

If you're running a MongoDB replica set, add specific monitoring for replica lag and election status.

groups:
name: mongodb.replica
  rules:
  - alert: MongoDBReplicaSetDown
    expr: mongodb_replset_number_of_members - mongodb_replset_number_of_members{state="PRIMARY"} - mongodb_replset_number_of_members{state="SECONDARY"} > 0
    for: 1m
    labels:
      severity: critical
    annotations:
      summary: "MongoDB replica set member down"
      description: "MongoDB replica set has unhealthy members."

  - alert: MongoDBNoPrimary
    expr: mongodb_replset_number_of_members{state="PRIMARY"} == 0
    for: 30s
    labels:
      severity: critical
    annotations:
      summary: "MongoDB replica set has no primary"
      description: "MongoDB replica set {{ $labels.set }} has no primary member."

Enable MongoDB profiler for slow query tracking

Configure MongoDB's built-in profiler to capture slow queries for analysis in your monitoring dashboard.

mongosh --host localhost:27017
use admin
db.runCommand({ profile: 2, slowms: 100 })
db.system.profile.createIndex({ "command.find": 1 })
db.system.profile.createIndex({ "command.aggregate": 1 })
exit

Configure index usage monitoring

Set up monitoring for index usage statistics to identify missing or unused indexes affecting performance.

groups:
name: mongodb.indexes
  rules:
  - alert: MongoDBCollectionScans
    expr: rate(mongodb_metrics_query_executor_total{state="collectionScans"}[5m]) > 10
    for: 2m
    labels:
      severity: warning
    annotations:
      summary: "High collection scans detected"
      description: "MongoDB is performing {{ $value }} collection scans per second, consider adding indexes."

  - alert: MongoDBHighIndexMisses
    expr: rate(mongodb_metrics_cursor_total{state="totalNoTimeout"}[5m]) / rate(mongodb_metrics_cursor_total{state="totalOpened"}[5m]) < 0.9
    for: 5m
    labels:
      severity: warning
    annotations:
      summary: "Low index hit ratio"
      description: "MongoDB index hit ratio is {{ $value | humanizePercentage }}, review query patterns."