Kube-probe TCP probe failed: connection timed out

The probe is unable to establish a connection to the application within the timeout period.

Understanding Kube-probe

Kube-probe is a diagnostic tool used within Kubernetes to monitor the health and readiness of applications running in a cluster. It helps ensure that applications are running smoothly by periodically checking their status and reporting any issues. Kube-probe can perform HTTP, TCP, and command-based checks to determine the health of an application.

Identifying the Symptom

One common issue encountered with Kube-probe is the error message: TCP probe failed: connection timed out. This indicates that the probe was unable to establish a connection to the application within the specified timeout period. This can lead to the application being marked as unhealthy, potentially triggering a restart or other corrective actions.

Exploring the Issue

The TCP probe failed: connection timed out error typically occurs when there is a delay in network communication between the probe and the application. This could be due to network latency, misconfigured network policies, or the application being too slow to respond. The probe attempts to connect to the specified port, and if it doesn't receive a response within the timeout period, it logs this error.

Common Causes

Network latency or congestion.
Incorrect probe configuration.
Application performance issues.

Steps to Fix the Issue

To resolve the TCP probe failed: connection timed out error, follow these steps:

1. Increase the Timeout Value

One of the simplest solutions is to increase the timeout value in the probe configuration. This gives the application more time to respond before the probe times out. You can modify the timeoutSeconds parameter in your probe configuration:

livenessProbe: tcpSocket: port: 8080 initialDelaySeconds: 10 timeoutSeconds: 5

Consider increasing timeoutSeconds to a higher value, such as 10 or 15 seconds, depending on your application's response time.

2. Investigate Network Latency

Check for any network latency issues that might be affecting communication between the probe and the application. Use tools like PingPlotter or Wireshark to analyze network traffic and identify potential bottlenecks.

3. Review Application Performance

If the application is slow to respond, investigate its performance. Check logs and metrics for any signs of resource exhaustion or bottlenecks. Consider scaling the application or optimizing its code to improve response times.

Conclusion

By understanding the root cause of the TCP probe failed: connection timed out error and following the steps outlined above, you can effectively resolve this issue and ensure your Kubernetes applications remain healthy and responsive. For more detailed information on configuring probes, refer to the Kubernetes documentation.

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The command executed by the exec probe returned a non-zero exit code, indicating failure.

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The application has crashed and is unable to respond to the liveness probe.

Kube-probe Readiness probe failed: resource limit exceeded

The application is unable to allocate necessary resources to handle the probe request.

Kube-probe TCP probe failed: network unreachable

The network is not properly configured, preventing the probe from reaching the application.

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The container has crashed or is not running.

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The application is not listening on the specified port, or the service is not running.

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The application is taking too long to respond to the readiness probe.

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