Memcached remains one of the most popular in-memory caching systems used to accelerate dynamic web applications by alleviating database load. However, without proper monitoring, it’s challenging to maintain optimal performance or troubleshoot bottlenecks effectively. For intermediate and advanced users, leveraging Prometheus and Grafana provides a powerful, scalable, and flexible monitoring solution tailored for Memcached environments.

Understanding how to extract, analyze, and visualize Memcached metrics is critical for maintaining low latency and high throughput. This post explores the technical aspects of integrating Memcached with Prometheus exporters and building Grafana dashboards to monitor key performance indicators (KPIs).

Why Use Prometheus and Grafana for Memcached?

Prometheus offers a robust time-series database designed for real-time monitoring, while Grafana excels at creating customizable and interactive dashboards. Together, they provide:

  • High-resolution metrics collection from Memcached servers
  • Alerting capabilities based on threshold breaches or anomalies
  • Visual insights into cache hit ratios, memory usage, network I/O, and more
  • Scalability to monitor multiple Memcached instances in distributed systems

This combination surpasses traditional monitoring tools by offering fine-grained data and flexible visualization, crucial in complex production environments.

Setting Up Memcached Exporter for Prometheus

To monitor Memcached, you need an exporter that exposes Memcached stats as Prometheus metrics:

  1. Choose the Memcached Exporter: The most commonly used is the prometheus/memcached_exporter. It scrapes Memcached’s stats and exposes them on an HTTP endpoint readable by Prometheus.

  2. Install and Configure the Exporter:

docker run -d -p 9150:9150 prom/memcached-exporter \
  -memcached.address your-memcached-host:11211

Alternatively, run it as a binary on your host with flags to specify Memcached connection details.

  1. Verify Metrics Exposure: Access http://<exporter-host>:9150/metrics to see raw Memcached metrics in Prometheus exposition format.

Key Memcached Metrics to Monitor

To gain actionable insights into Memcached performance, focus on these metrics:

  • memcached_cmd_get_total: Total GET commands received — a high value indicates frequent cache reads.
  • memcached_cmd_set_total: Total SET commands — helps gauge cache writes.
  • memcached_get_hits_total and memcached_get_misses_total: Crucial for calculating cache hit ratio, a direct indicator of cache effectiveness.
  • memcached_bytes: Current memory usage by Memcached.
  • memcached_curr_connections: Number of active client connections.
  • memcached_evictions_total: Number of items evicted due to memory pressure — a red flag for insufficient cache size.
  • memcached_reclaimed_total: Number of expired items reclaimed.

Tracking these metrics over time allows proactive scaling and tuning.

Configuring Prometheus to Scrape the Exporter

Add the following scrape config to your prometheus.yml:

scrape_configs:
  - job_name: 'memcached'
    static_configs:
      - targets: ['your-exporter-host:9150']

Reload Prometheus to apply changes. Confirm scraping by querying metrics like memcached_cmd_get_total in Prometheus UI.

Building Grafana Dashboards for Visualization

Grafana’s flexibility lets you create tailored dashboards for Memcached monitoring:

  1. Import a Prebuilt Dashboard: Numerous open-source Memcached dashboards are available on Grafana’s dashboard repository. Import them as a starting point.

  2. Customize Panels for Critical Metrics:

  • Cache Hit Ratio Panel
    Use PromQL: 
    rate(memcached_get_hits_total[5m]) / (rate(memcached_get_hits_total[5m]) + rate(memcached_get_misses_total[5m]))

  • Memory Usage Over Time
    Track memcached_bytes to monitor memory footprint trends.

  • Evictions Alert Panel
    Visualize memcached_evictions_total spikes indicating pressure.

  1. Set Alerts and Thresholds: Configure Grafana alerts to notify on low cache hit ratios (e.g., below 80%) or high evictions.

  2. Create Summary Panels: Combine key metrics for quick health checks, including connections, commands per second, and reclaim counts.

Advanced Tips for Scaling Memcached Monitoring

  • Multi-instance Monitoring: Label exporters by instance to aggregate metrics from clustered Memcached nodes.
  • Use Recording Rules in Prometheus: Precompute expensive queries like hit ratios to improve dashboard responsiveness.
  • Leverage Grafana Variables: Allow dynamic selection of Memcached instances or environments.
  • Integrate with Alertmanager: Automate incident response for critical performance degradations.

Performance Optimization Insights

Monitoring alone is not enough — use insights from Prometheus and Grafana to:

  • Adjust cache size to reduce evictions.
  • Optimize client connection pools based on connection metrics.
  • Tune TTL settings by analyzing item reclaim rates.
  • Detect anomalous traffic patterns impacting Memcached stability.

Conclusion

For intermediate and advanced users managing Memcached at scale, combining Prometheus and Grafana delivers a comprehensive monitoring solution that enhances visibility, troubleshooting, and performance tuning. By carefully selecting exporters, configuring Prometheus scraping, and customizing Grafana dashboards, you can maintain a high-performing cache layer critical for application responsiveness and scalability.

Implementing this monitoring stack not only improves operational efficiency but also supports proactive infrastructure management, directly contributing to better user experience and cost optimization. Start integrating Prometheus and Grafana into your Memcached ecosystem today to unlock these benefits.