VMs / EC2 High Number of Open Connections

The number of open connections is higher than expected.

Understanding Prometheus and Its Purpose

Prometheus is an open-source systems monitoring and alerting toolkit originally built at SoundCloud. It is designed for reliability and scalability, providing powerful querying capabilities and a flexible data model. Prometheus is widely used for monitoring cloud environments, including VMs and EC2 instances, to ensure optimal performance and availability.

Symptom: High Number of Open Connections

One of the alerts you might encounter when using Prometheus with VMs or EC2 instances is the 'High Number of Open Connections' alert. This alert indicates that the number of open connections on your server is higher than expected, which could lead to performance degradation or even service outages.

Details About the Alert

The 'High Number of Open Connections' alert is triggered when the number of active connections exceeds a predefined threshold. This can happen due to various reasons, such as inefficient connection handling in your application, a sudden spike in traffic, or a potential denial-of-service attack. Monitoring open connections is crucial because it helps in identifying potential bottlenecks and ensuring that your application can handle the load efficiently.

Why This Alert Matters

Open connections consume system resources, and an excessive number can lead to resource exhaustion, causing your application to slow down or crash. By addressing this alert promptly, you can prevent downtime and maintain a smooth user experience.

Steps to Fix the Alert

1. Review Application Configurations

Start by reviewing your application's configuration settings. Ensure that connection pooling is properly configured to reuse existing connections rather than opening new ones unnecessarily. For example, if you are using a database, check the connection pool settings in your database client library.

2. Optimize Connection Handling

Implement best practices for connection handling in your application code. This includes closing connections when they are no longer needed and using connection pooling libraries to manage connections efficiently. For instance, in Java applications, you can use libraries like HikariCP or Apache DBCP for efficient connection pooling.

3. Monitor Traffic Patterns

Analyze your traffic patterns to identify any unusual spikes that might be causing the increase in open connections. Use Prometheus queries to visualize connection metrics over time. For example, you can use the following query to monitor the number of open connections:

sum(rate(node_network_receive_packets_total[5m]))

Adjust your infrastructure accordingly to handle peak loads.

4. Investigate Potential Security Threats

If you suspect a denial-of-service attack, implement security measures such as rate limiting and IP whitelisting to protect your application. Tools like AWS WAF can help mitigate such threats by filtering malicious traffic.

Additional Resources

For more information on optimizing connection handling, you can refer to the Prometheus Documentation and the AWS EC2 Documentation. These resources provide comprehensive guides on monitoring and managing your cloud infrastructure effectively.

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