Troubleshooting guide#

This document addresses common inquiries. If you don’t find an answer to your question here, please don’t hesitate to connect with us via our community channels.

Contents#

Upgrade KubeRay
Worker init container
Cluster domain
RayService
Autoscaler
Other questions

Upgrade KubeRay#

If you have issues upgrading KubeRay, refer to the upgrade guide. Most issues are about the CRD version.

Worker init container#

The KubeRay operator injects a default init container into every worker Pod. This init container is responsible for waiting until the Global Control Service (GCS) on the head Pod is ready before establishing a connection to the head. The init container will use ray health-check to check the GCS server status continuously.

The default worker init container may not work for all use cases, or users may want to customize the init container.

1. Init container troubleshooting#

Some common causes for the worker init container to stuck in Init:0/1 status are:

The GCS server process has failed in the head Pod. Please inspect the log directory /tmp/ray/session_latest/logs/ in the head Pod for errors related to the GCS server.
The ray executable is not included in the $PATH for the image, so the init container will fail to run ray health-check.
The CLUSTER_DOMAIN environment variable is not set correctly. See the section cluster domain for more details.
The worker init container shares the same ImagePullPolicy, SecurityContext, Env, VolumeMounts, and Resources as the worker Pod template. Sharing these settings is possible to cause a deadlock. See #1130 for more details.

If the init container remains stuck in Init:0/1 status for 2 minutes, we will stop redirecting the output messages to /dev/null and instead print them to the worker Pod logs. To troubleshoot further, you can inspect the logs using kubectl logs.

2. Disable the init container injection#

If you want to customize the worker init container, you can disable the init container injection and add your own. To disable the injection, set the ENABLE_INIT_CONTAINER_INJECTION environment variable in the KubeRay operator to false (applicable from KubeRay v0.5.2). Please refer to #1069 and the KubeRay Helm chart for instructions on how to set the environment variable. Once disabled, you can add your custom init container to the worker Pod template.

Cluster domain#

In KubeRay, we use Fully Qualified Domain Names (FQDNs) to establish connections between workers and the head. The FQDN of the head service is ${HEAD_SVC}.${NAMESPACE}.svc.${CLUSTER_DOMAIN}. The default cluster domain is cluster.local, which works for most Kubernetes clusters. However, it’s important to note that some clusters may have a different cluster domain. You can check the cluster domain of your Kubernetes cluster by checking /etc/resolv.conf in a Pod.

To set a custom cluster domain, adjust the CLUSTER_DOMAIN environment variable in the KubeRay operator. Helm chart users can make this modification here. For more information, please refer to #951 and #938 for more details.

RayService#

RayService is a Custom Resource Definition (CRD) designed for Ray Serve. In KubeRay, creating a RayService will first create a RayCluster and then create Ray Serve applications once the RayCluster is ready. If the issue pertains to the data plane, specifically your Ray Serve scripts or Ray Serve configurations (serveConfigV2), troubleshooting may be challenging. See rayservice-troubleshooting for more details.

Ray Autoscaler#

Ray Autoscaler doesn’t scale up, causing new Ray tasks or actors to remain pending#

One common cause is that the Ray tasks or actors require an amount of resources that exceeds what any single Ray node can provide. Note that Ray tasks and actors represent the smallest scheduling units in Ray, and a task or actor should be on a single Ray node. Take kuberay#846 as an example. The user attempts to schedule a Ray task that requires 2 CPUs, but the Ray Pods available for these tasks have only 1 CPU each. Consequently, the Ray Autoscaler decides not to scale up the RayCluster.