mirror of https://github.com/dapr/docs.git
84 lines
4.5 KiB
Markdown
84 lines
4.5 KiB
Markdown
# Health
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Dapr provides a way to determine it's health using an HTTP /healthz endpoint.
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With this endpoint, the Dapr process, or sidecar, can be probed for its health and hence determine its readiness and liveness. See [health API ](../../reference/api/health_api.md)
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The Dapr `/healthz` endpoint can be used by health probes from the application hosting platform. This topic describes how Dapr integrates with probes from different hosting platforms.
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As a user, when deploying Dapr to a hosting platform (for example Kubernetes), the Dapr health endpoint is automatically configured for you. There is nothing you need to configure.
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Note: Dapr actors also have a health API endpoint where Dapr probes the application for a response to a signal from Dapr that the actor application is healthy and running. See [actor health API](../../reference/api/actors_api.md#health-check)
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## Health endpoint: Integration with Kubernetes
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Kubernetes uses *readiness* and *liveness* probes to determines the health of the container.
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The kubelet uses liveness probes to know when to restart a container.
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For example, liveness probes could catch a deadlock, where an application is running, but unable to make progress. Restarting a container in such a state can help to make the application more available despite having bugs.
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The kubelet uses readiness probes to know when a container is ready to start accepting traffic. A pod is considered ready when all of its containers are ready. One use of this readiness signal is to control which Pods are used as backends for Kubernetes services. When a pod is not ready, it is removed from Kubernetes service load balancers.
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When integrating with Kubernetes, the Dapr sidecar is injected with a Kubernetes probe configuration telling it to use the Dapr healthz endpoint. This is done by the `Sidecar Injector` system service. The integration with the kubelet is shown in the diagram below.
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### How to configure a liveness probe in Kubernetes
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In the pod configuration file, the liveness probe is added in the containers spec section as shown below :
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```
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livenessProbe:
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httpGet:
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path: /healthz
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port: 8080
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initialDelaySeconds: 3
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periodSeconds: 3
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```
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In the above *example*, the `periodSeconds` field specifies that the kubelet should perform a liveness probe every 3 seconds. The `initialDelaySeconds` field tells the kubelet that it should wait 3 seconds before performing the first probe. To perform a probe, the kubelet sends an HTTP GET request to the server that is running in the container and listening on port 8080 in this example. If the handler for the server’s /healthz path returns a success code, the kubelet considers the container to be alive and healthy. If the handler returns a failure code, the kubelet kills the container and restarts it.
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Any code greater than or equal to 200 and less than 400 indicates success. Any other code indicates failure.
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### How to configure a readiness probe in Kubernetes
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Readiness probes are configured similarly to liveness probes. The only difference is that you use the `readinessProbe` field instead of the `livenessProbe` field.
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```
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readinessProbe:
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httpGet:
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path: /healthz
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port: 8080
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initialDelaySeconds: 3
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periodSeconds: 3
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```
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### How the Dapr sidecar health endpoint is configured with Kubernetes
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As mentioned above, this configuration is done automatically by the Sidecar Injector service. This section describes the specific values that are set on the liveness and readiness probes.
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Dapr has its HTTP health endpoint `/v1.0/healthz` on port 3500, This can be used with Kubernetes for readiness and liveness probe. When the Dapr sidecar is injected , the readiness and liveness probes are configured in the pod configuration file with the following values.
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```
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livenessProbe:
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httpGet:
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path: v1.0/healthz
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port: 3500
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initialDelaySeconds: 5
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periodSeconds: 10
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timeoutSeconds : 5
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failureThreshold : 3
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readinessProbe:
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httpGet:
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path: v1.0/healthz
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port: 3500
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initialDelaySeconds: 5
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periodSeconds: 10
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timeoutSeconds : 5
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failureThreshold: 3
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```
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For more information refer to;
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- [ Endpoint health API](../../reference/api/health_api.md)
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- [Actor health API](../../reference/api/actors_api.md#health-check)
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- [Kubernetes probe configuration parameters](https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/)
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