When deploying an application in a GKE cluster, which probe should be used to check if a pod is ready to accept traffic?

The readiness probe is specifically designed to determine if a pod is ready to accept traffic. This probe checks the application's ability to function correctly and serve requests. When a readiness probe is configured, Kubernetes uses it to assess the state of the application within the pod. If the probe fails, Kubernetes understands that the pod is not ready, and as a result, it will not direct traffic to that pod. This helps ensure that users do not experience errors or downtime when interacting with the application.

Liveness probes, on the other hand, are intended to check if a pod is still running. If a liveness probe fails, Kubernetes will restart the pod, but it does not affect the traffic routing while the pod is still considered 'running'.

Load balancer health checks focus on the overall health of the service at the load balancer level but do not provide granular insights at the pod or application level. Health checks, in general, can refer to any checks but are not specific types of probes defined within Kubernetes.

The readiness probe is thus the correct choice for checking if a pod can handle traffic, distinguishing it from the functions of other types of probes and checks.