open-consul/website/content/docs/k8s/connect/health.mdx

---
layout: docs
page_title: Configure Health Checks for Consul on Kubernetes
description: >-
Kubernetes has built-in health probes you can sync with Consul's health checks to ensure service mesh traffic is routed to healthy pods. Learn how to register a TTL Health check and use mutating webhooks to redirect k8s liveness, readiness, and startup probes through Envoy proxies.
---

# Configure Health Checks for Consul on Kubernetes

~> This topic requires familiarity with [Kubernetes Health Checks](https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/).

This page describes how Consul on Kubernetes will sync the status of Kubernetes health probes of a pod to Consul for service mesh use cases.
Health check synchronization with Consul is done automatically whenever `connectInject.enabled` is `true`.

For each Kubernetes pod that is connect-injected the following will be configured:

1. A [TTL health check](/docs/discovery/checks#ttl) is registered within Consul.
The Consul health check's state will reflect the pod's readiness status,
which is the combination of all Kubernetes probes registered with the pod.

1. If the pod is utilizing [Transparent Proxy](/docs/connect/transparent-proxy) mode, the mutating webhook will mutate all `http` based Startup, Liveness, and Readiness probes in the pod to redirect through the Envoy proxy.
This is done with [`ExposePaths` configuration](/docs/connect/registration/service-registration#expose-paths-configuration-reference) for each probe so that kubelet can access the endpoint through the Envoy proxy.

~> The mutation behavior can be disabled by either setting the `consul.hashicorp.com/transparent-proxy-overwrite-probes` pod annotation to `false` or the `connectInject.defaultOverwriteProbes` Helm value to `false`.

When readiness probes are set for a pod, the status of the pod will be reflected within Consul and will cause Consul to redirect service
mesh traffic to the pod based on the pod's health. If the pod has failing health checks, Consul will no longer use
the service instance associated with the pod for service mesh traffic. When the pod passes its health checks, Consul will
then use the respective service instance for service mesh traffic.

In the case where no user defined health checks are assigned to a pod, the default behavior is that the Consul health check will
be marked `passing` until the pod becomes unready.

-> It is highly recommended to [enable TLS](/docs/k8s/helm#v-global-tls-enabled) for all production configurations to mitigate any
security concerns should the pod network ever be compromised. The controller makes calls across the network to Consul agents on all
nodes so an attacker could potentially sniff ACL tokens *if those calls are not encrypted* via TLS.