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Updating Liveness and Readiness Docs #3494
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@@ -173,11 +173,25 @@ the Container has been restarted: | |
kubectl describe pod liveness-http | ||
``` | ||
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## Defining a TCP liveness probe | ||
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A third type of liveness probe uses a TCP Socket. With this configuration, the | ||
Kubelet will attempt to open a socket to your container on the specified port. | ||
If it can establish a connection, the container is considered healthy, if it | ||
can’t it is considered a failure. | ||
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{% include code.html language="yaml" file="tcp-liveness.yaml" ghlink="/docs/tasks/configure-pod-container/tcp-liveness.yaml" %} | ||
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As you can see, configuration for a TCP check is quite similar to a HTTP check. | ||
In this example, the kubelet will attempt to connect to the `goproxy` container | ||
on port 8080, with the first check happening 15 seconds after the container | ||
starts. The kubelet will repeat this check every 20 seconds. | ||
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## Using a named port | ||
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You can use a named | ||
[ContainerPort](/docs/api-reference/v1.6/#containerport-v1-core) | ||
for HTTP liveness checks: | ||
for HTTP or TCP liveness checks: | ||
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```yaml | ||
ports: | ||
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@@ -214,29 +228,45 @@ readinessProbe: | |
periodSeconds: 5 | ||
``` | ||
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{% endcapture %} | ||
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Configuration for HTTP and TCP readiness probes also remains identical to | ||
liveness probes. | ||
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{% capture discussion %} | ||
Readiness and liveness probes can be used in parallel for the same container. | ||
Using both can ensure that traffic does not reach a container that isnot ready | ||
for it, and that containers are restarted when they fail. | ||
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## Discussion | ||
## Configuring Probes | ||
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{% comment %} | ||
Eventually, some of this Discussion section could be moved to a concept topic. | ||
Eventually, some of this section could be moved to a concept topic. | ||
{% endcomment %} | ||
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[Probes](/docs/api-reference/v1.6/#probe-v1-core) have these additional fields that you can use to more precisely control the behavior of liveness and readiness checks: | ||
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* timeoutSeconds | ||
* successThreshold | ||
* failureThreshold | ||
[Probes](/docs/api-reference/v1.6/#probe-v1-core) have a number of fields that | ||
you can use to more precisely control the behavior of liveness and readiness | ||
checks: | ||
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* `initialDelaySeconds`: Number of seconds after the container has started | ||
before liveness probes are initiated. | ||
* `periodSeconds`: How often (in seconds) to perform the probe. Default to 10 | ||
seconds. Minimum value is 1. | ||
* `timeoutSeconds`: Number of seconds after which the probe times out. Defaults | ||
to 1 second. Minimum value is 1. | ||
* `successThreshold`: Minimum consecutive successes for the probe to be | ||
considered successful after having failed. Defaults to 1. Must be 1 for | ||
liveness. Minimum value is 1. | ||
* `failureThreshold`: Minimum consecutive failures for the probe to be | ||
considered failed after having succeeded. Defaults to 3. Minimum value is 1. | ||
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[HTTP probes](/docs/api-reference/v1.6/#httpgetaction-v1-core) | ||
have these additional fields: | ||
have additional fields that can be set on `httpGet`: | ||
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* host | ||
* scheme | ||
* httpHeaders | ||
* `host`: Host name to connect to, defaults to the pod IP. You probably want to | ||
set "Host" in httpHeaders instead. | ||
* `scheme`: Custom headers to set in the request. HTTP allows repeated headers. | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. This is incorrect. You describe |
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* `httpHeaders`: Path to access on the HTTP server. | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Again incorrect. |
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* `port`: Name or number of the port to access on the container. Number must be | ||
in the range 1 to 65535. | ||
* `scheme`: Scheme to use for connecting to the host. Defaults to HTTP. | ||
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For an HTTP probe, the kubelet sends an HTTP request to the specified path and | ||
port to perform the check. The kubelet sends the probe to the container’s IP address, | ||
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@@ -247,9 +277,6 @@ where you would set it. Suppose the Container listens on 127.0.0.1 and the Pod's | |
If your pod relies on virtual hosts, which is probably the more common case, | ||
you should not use `host`, but rather set the `Host` header in `httpHeaders`. | ||
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In addition to command probes and HTTP probes, Kubernetes supports | ||
[TCP probes](/docs/api-reference/v1.6/#tcpsocketaction-v1-core). | ||
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{% endcapture %} | ||
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{% capture whatsnext %} | ||
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@@ -258,7 +285,7 @@ In addition to command probes and HTTP probes, Kubernetes supports | |
[Container Probes](/docs/concepts/workloads/pods/pod-lifecycle/#container-probes). | ||
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* Learn more about | ||
[Health Checking section](/docs/user-guide/walkthrough/k8s201/#health-checking). | ||
[Health Checking](/docs/user-guide/walkthrough/k8s201/#health-checking). | ||
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### Reference | ||
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@@ -0,0 +1,17 @@ | ||
apiVersion: v1 | ||
kind: Pod | ||
metadata: | ||
name: goproxy | ||
labels: | ||
app: goproxy | ||
spec: | ||
containers: | ||
- name: goproxy | ||
image: gcr.io/google_containers/goproxy:0.1 | ||
ports: | ||
- containerPort: 8080 | ||
readinessProbe: | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. The name of this yaml says |
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tcpSocket: | ||
port: 8080 | ||
initialDelaySeconds: 15 | ||
periodSeconds: 20 |
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
nit:
s/isnot/is not/g