Monitoring and metrics are crucial for maintaining the health, performance, and reliability of your Redis instances. This section will cover the tools and techniques you can use to monitor Redis, understand its performance metrics, and ensure it runs smoothly in production.

1. Monitoring: The process of continuously observing the state of your Redis instances to detect issues and ensure optimal performance.
2. Metrics: Quantitative data points that provide insights into the performance and health of your Redis instances.
3. Alerting: Setting up notifications to inform you when certain metrics exceed predefined thresholds.

1. INFO Command: Provides a wealth of information about the Redis server, including memory usage, CPU usage, keyspace statistics, and more.

   redis-cli INFO
   

   • Sections: The INFO command output is divided into sections like Server, Clients, Memory, Persistence, Stats, Replication, CPU, Keyspace, etc.
   • Example:

     # Server
     redis_version:6.2.1
     redis_git_sha1:00000000
     redis_git_dirty:0
     redis_build_id:1c1ae1b1b1b1b1b1
     redis_mode:standalone
     os:Linux 4.15.0-112-generic x86_64
     arch_bits:64
     multiplexing_api:epoll
     

2. MONITOR Command: Streams every command processed by the Redis server in real-time.

   redis-cli MONITOR
   

   • Use Case: Useful for debugging and understanding the workload on your Redis instance.
   • Example:

     1616161616.161161 [0 127.0.0.1:6379] "SET" "key" "value"
     

1. Redis Exporter for Prometheus: A Prometheus exporter for Redis metrics.

   • Installation:

     docker run --name redis_exporter -d -p 9121:9121 oliver006/redis_exporter
     

   • Metrics: Exposes Redis metrics in a format that Prometheus can scrape.
   • Example: redis_up, redis_commands_processed_total, redis_memory_used_bytes.

2. Grafana: A visualization tool that can be used with Prometheus to create dashboards for Redis metrics.

   • Setup: Connect Grafana to Prometheus and create dashboards to visualize Redis metrics.
   • Example: Create a dashboard to monitor memory usage, command rates, and latency.

• used_memory: Total number of bytes allocated by Redis.
• used_memory_rss: Number of bytes that Redis has allocated as seen by the operating system.
• used_memory_peak: Peak memory consumed by Redis.

• total_commands_processed: Total number of commands processed by the server.
• instantaneous_ops_per_sec: Number of commands processed per second.
• total_net_input_bytes: Total number of bytes read from the network.
• total_net_output_bytes: Total number of bytes sent to the network.

• rdb_changes_since_last_save: Number of changes to the dataset since the last RDB save.
• aof_rewrite_in_progress: Flag indicating if an AOF rewrite operation is in progress.

• connected_slaves: Number of connected replicas.
• master_repl_offset: The replication offset of the master.

1. Download Prometheus:

   wget https://github.com/prometheus/prometheus/releases/download/v2.26.0/prometheus-2.26.0.linux-amd64.tar.gz
   tar xvfz prometheus-2.26.0.linux-amd64.tar.gz
   cd prometheus-2.26.0.linux-amd64
   

2. Configure Prometheus:

   • Edit prometheus.yml to add the Redis exporter as a target.

     scrape_configs:
       - job_name: 'redis'
         static_configs:
           - targets: ['localhost:9121']
     

3. Start Prometheus:

   ./prometheus --config.file=prometheus.yml
   

1. Download and Install Grafana:

   sudo apt-get install -y adduser libfontconfig1
   wget https://dl.grafana.com/oss/release/grafana_7.5.2_amd64.deb
   sudo dpkg -i grafana_7.5.2_amd64.deb
   

2. Start Grafana:

   sudo systemctl start grafana-server
   sudo systemctl enable grafana-server
   

3. Configure Grafana:

   • Open Grafana in your browser (http://localhost:3000).
   • Add Prometheus as a data source.
   • Create a dashboard and add panels to visualize Redis metrics.

1. Task: Use the INFO command to retrieve and analyze the memory usage of your Redis instance.
2. Solution:

   redis-cli INFO memory
   

   • Expected Output:

     # Memory
     used_memory:1024000
     used_memory_human:1000K
     used_memory_rss:2048000
     used_memory_peak:3072000
     

1. Task: Set up the Redis Exporter for Prometheus and verify that Prometheus is scraping Redis metrics.
2. Solution:
   • Follow the steps in the "Practical Example" section to set up the Redis Exporter and Prometheus.
   • Verify by accessing Prometheus at http://localhost:9090 and checking the Targets page.

1. Task: Create a Grafana dashboard to monitor Redis memory usage and command rates.
2. Solution:
   • Follow the steps in the "Practical Example" section to set up Grafana.
   • Create a new dashboard and add panels for used_memory and instantaneous_ops_per_sec.

• Mistake: Not setting up alerts for critical metrics.

  • Tip: Always configure alerts for key metrics like memory usage, command rates, and replication status to get notified of potential issues.

• Mistake: Overlooking the importance of monitoring persistence metrics.

  • Tip: Monitor RDB and AOF metrics to ensure data durability and understand the impact of persistence operations on performance.

In this section, we covered the importance of monitoring and metrics for Redis, explored various tools and techniques for monitoring Redis instances, and learned how to set up a monitoring stack using Prometheus and Grafana. By keeping a close eye on key metrics, you can ensure the health and performance of your Redis deployments, quickly identify and resolve issues, and optimize your Redis instances for better performance.