[BUG] Load Balancer Connectivity After Pod Restarts

[EmAchieng]

Kube-OVN Version

1.13.2

Description

We encountered an issue with a load balancer rule on a Kubernetes cluster. The load balancer was configured to route traffic to a specific VIP. Everything worked fine until the router pods were restarted. After the restart, connectivity to the VIP broke, and the load balancer rule no longer functioned as expected.

To resolve the issue, we updated the VIP to a new IP address. This triggered an update to the load balancer rule, and the pods were recreated to point to the new VIP. After this, connectivity was restored, and everything worked as expected.

It seems like the logic behind the load balancer rule broke at some point, but the issue only became apparent after the pod restarts terminated the existing connections.

What could cause a load balancer rule to stop functioning after pod restarts, and how to prevent this from happening in future?

[dosubot]

Hello @EmAchieng! I'm Dosu, your friendly bot here to help you tackle bugs, answer questions, and guide you on your journey to becoming a contributor. I'm here to assist while you wait for a human maintainer. Let's get to the bottom of this issue! 🐙

The issue with the load balancer rule stopping after pod restarts in Kube-OVN version 1.13.2 could be due to a failure in reinitializing the NAT rules for the load balancer service pod. The function checkAndReInitLbSvcPod is responsible for ensuring that NAT rules are correctly set up when a pod is running. If this function does not execute successfully, the load balancer rules may not be applied correctly after a pod restart.

To prevent this issue in the future, consider the following steps:

1. Ensure that the checkAndReInitLbSvcPod function is correctly updating the service's attachment network and load balancer IP.
2. Verify that the pod is running and has the correct labels indicating it is part of a load balancer service.
3. Ensure that the updatePodAttachNets function is successfully executing NAT rules to set up the load balancer IP and DNAT rules.
4. Confirm that the service status is updated with the correct load balancer IP.
5. Implement and verify load balancer health checks using the AddLoadBalancerHealthCheck function to ensure the load balancer is functioning correctly.

Additionally, check for any errors in the logs related to the execution of NAT rules, updates to the service status, or health check failures. Regularly updating to the latest version of Kube-OVN may also help prevent similar issues, as updates often include bug fixes and improvements ^[1][2][3][4].

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[EmAchieng]

Daer @dosu, are there specific log entries or error patterns that could help identify issues with the NAT rule execution, service status updates or health check failures?

[dosubot]

For identifying issues with NAT rule execution, service status updates, or health check failures in Kube-OVN, you can look for specific log entries and error patterns:

1. Service Status Updates:

   • Successful updates are logged with:

     "handle update service <service_key>"
     

   • Failed updates log errors like:

     "failed to get vpc <vpc_name> of lb, <error>"
     

2. Health Check Failures:

   • Missing load balancer name or VIP endpoint:

     "the lb name is required" or "the vip endpoint is required"
     

   • Errors during health check creation or transaction:

     "failed to create lb health check for lb <lb_name> vip <vip_endpoint>: <error>"
     

Unfortunately, I couldn't find specific log entries for NAT rule execution issues in the available data. However, checking for errors related to the updatePodAttachNets function might provide insights if NAT rules are not being applied correctly ^[1][2].

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[EmAchieng]

@dosu, What are the common reasons for Kube-OVN switch-load-balancer resources to degrade or break over time?

[dosubot]

Common reasons for Kube-OVN switch-load-balancer resources to degrade or break over time include:

1. Configuration Drift: Changes in network configurations, such as updates to network attachment definitions or annotations, can lead to inconsistencies if not properly managed.

2. Pod Restarts: As mentioned earlier, pod restarts can disrupt NAT rules and load balancer configurations if the reinitialization processes do not execute correctly.

3. Resource Constraints: Insufficient resources (CPU, memory) on nodes can lead to degraded performance or failure of load balancer components.

4. Network Policy Changes: Modifications to network policies or security groups can inadvertently block traffic to or from the load balancer.

5. Software Bugs: Bugs in the Kube-OVN codebase or dependencies can cause unexpected behavior or failures in load balancer operations.

6. Version Mismatches: Running incompatible versions of Kube-OVN components or dependencies can lead to failures or degraded performance.

7. Health Check Failures: If health checks are not properly configured or fail to execute, the load balancer may not function as expected.

Regular monitoring, logging, and updates can help mitigate these issues and ensure the stability of load balancer resources.

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[EmAchieng]

@dosu, Beyond the logs mentioned (e.g., "failed to get vpc <vpc_name>" or "failed to create lb health check"), are there other log patterns or debugging steps we should also focus on?

[dosubot]

In addition to the logs previously mentioned, you should also focus on the following log patterns and debugging steps to identify issues with Kube-OVN:

1. NAT Rule Execution:

   • Look for errors related to the creation, patching, or deletion of iptables DNAT rules. These might include:

     "Error creating iptables dnat"
     "Failed to delete iptables dnat"
     

2. Service Status Updates:

   • Check for errors indicating issues with node or interface retrieval, such as:

     "failed to get node %s %v"
     "failed to find iface %s, %v"
     

3. Interface and IP Address Issues:

   • Logs indicating interface or IP address problems can be crucial:

     "iface %v is down"
     "iface %s has no ip address"
     

4. SNAT Update Failures:

   • Errors during SNAT updates can affect load balancer functionality:

     "failed to update snat %s, vpc changed"
     "failed to update snat %s, no external ip"
     

5. General Debugging Steps:

   • Verify that all pods are running and have the correct labels.
   • Ensure that the network attachment definitions are correctly configured.
   • Check resource usage on nodes to ensure there are no constraints.
   • Review any recent changes to network policies or configurations that might affect connectivity.

These additional log patterns and steps can help you pinpoint issues affecting the load balancer and NAT rule execution in Kube-OVN ^[1][2][3].

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[oilbeater]

@EmAchieng it looks like a bug can you give reproduce steps so we can try to fix it.

[abasitt]

sounds similar to this ? #5029