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Add readme for kubernetes-overlord-extensions and update docs (#14674) 

* Add readme for kubernetes task scheduler

* clean up uneeded stuff

* Update extensions-contrib/kubernetes-overlord-extensions/README.md

Co-authored-by: Abhishek Agarwal <1477457+abhishekagarwal87@users.noreply.github.com>

* Move documentation into main page

* indentation

* cleanup spellcheck errors

* Update docs/development/extensions-contrib/k8s-jobs.md

Co-authored-by: Suneet Saldanha <suneet@apache.org>

* Update extensions-contrib/kubernetes-overlord-extensions/README.md

Co-authored-by: Suneet Saldanha <suneet@apache.org>

* Update docs/development/extensions-contrib/k8s-jobs.md

Co-authored-by: Suneet Saldanha <suneet@apache.org>

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* Update docs/development/extensions-contrib/k8s-jobs.md

Co-authored-by: Suneet Saldanha <suneet@apache.org>

* Update docs/development/extensions-contrib/k8s-jobs.md

Co-authored-by: Suneet Saldanha <suneet@apache.org>

* Update docs/development/extensions-contrib/k8s-jobs.md

Co-authored-by: Suneet Saldanha <suneet@apache.org>

---------

Co-authored-by: Abhishek Agarwal <1477457+abhishekagarwal87@users.noreply.github.com>
Co-authored-by: Suneet Saldanha <suneet@apache.org>
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@ -28,73 +28,33 @@ Consider this an [EXPERIMENTAL](../experimental.md) feature mostly because it ha
## How it works ## How it works
The K8s extension builds a pod spec using the specified pod adapter, the default implementation takes the podSpec of your `Overlord` pod and creates a kubernetes job from this podSpec. Thus if you have sidecars such as Splunk or Istio it can optionally launch a task as a K8s job. All jobs are natively restorable, they are decoupled from the druid deployment, thus restarting pods or doing upgrades has no affect on tasks in flight. They will continue to run and when the overlord comes back up it will start tracking them again. The K8s extension builds a pod spec for each task using the specified pod adapter. All jobs are natively restorable, they are decoupled from the Druid deployment, thus restarting pods or doing upgrades has no affect on tasks in flight. They will continue to run and when the overlord comes back up it will start tracking them again.
## Pod Adapters
The logic defining how the pod template is built for your kubernetes job depends on which pod adapter you have specified.
### Overlord Single Container Pod Adapter
The overlord single container pod adapter takes the podSpec of your `Overlord` pod and creates a kubernetes job from this podSpec. This is the default pod adapter implementation, to explicitly enable it you can specify the runtime property `druid.indexer.runner.k8s.adapter.type: overlordSingleContainer`
### Overlord Multi Container Pod Adapter
The overlord multi container pod adapter takes the podSpec of your `Overlord` pod and creates a kubernetes job from this podSpec. It uses kubexit to manage dependency ordering between the main container that runs your druid peon and other sidecars defined in the `Overlord` pod spec. To enable this pod adapter you can specify the runtime property `druid.indexer.runner.k8s.adapter.type: overlordMultiContainer`
### Custom Template Pod Adapter
The custom template pod adapter allows you to specify a pod template file per task type. This adapter requires you to specify a `base` pod spec which will be used in the case that a task specific pod spec has not been defined. To enable this pod adapter you can specify the runtime property `druid.indexer.runner.k8s.adapter.type: customTemplateAdapter`
The base pod template must be specified as the runtime property `druid.indexer.runner.k8s.podTemplate.base: /path/to/basePodSpec.yaml`
Task specific pod templates must be specified as the runtime property `druid.indexer.runner.k8s.podTemplate.{taskType}: /path/to/taskSpecificPodSpec.yaml` where {taskType} is the name of the task type i.e `index_parallel`
## Configuration ## Configuration
To use this extension please make sure to [include](../../configuration/extensions.md#loading-extensions)`druid-kubernetes-overlord-extensions` in the extensions load list for your overlord process. To use this extension please make sure to [include](../../configuration/extensions.md#loading-extensions)`druid-kubernetes-overlord-extensions` in the extensions load list for your overlord process.
The extension uses the task queue to limit how many concurrent tasks (K8s jobs) are in flight so it is required you have a reasonable value for `druid.indexer.queue.maxSize`. Additionally set the variable `druid.indexer.runner.namespace` to the namespace in which you are running druid. The extension uses `druid.indexer.runner.capacity` to limit the number of k8s jobs in flight. A good initial value for this would be the sum of the total task slots of all the middle managers you were running before switching to K8s based ingestion. The K8s task runner uses one thread per Job that is created, so setting this number too large can cause memory issues on the overlord. Additionally set the variable `druid.indexer.runner.namespace` to the namespace in which you are running druid.
Other configurations required are: Other configurations required are:
`druid.indexer.runner.type: k8s` and `druid.indexer.task.encapsulatedTask: true` `druid.indexer.runner.type: k8s` and `druid.indexer.task.encapsulatedTask: true`
You can add optional labels to your K8s jobs / pods if you need them by using the following configuration: ## Pod Adapters
`druid.indexer.runner.labels: '{"key":"value"}'` The logic defining how the pod template is built for your Kubernetes Job depends on which pod adapter you have specified.
Annotations are the same with:
`druid.indexer.runner.annotations: '{"key":"value"}'`
All other configurations you had for the middle manager tasks must be moved under the overlord with one caveat, you must specify javaOpts as an array: ### Overlord Single Container Pod Adapter/Overlord Multi Container Pod Adapter
`druid.indexer.runner.javaOptsArray`, `druid.indexer.runner.javaOpts` is no longer supported. The overlord single container pod adapter takes the podSpec of your `Overlord` pod and creates a kubernetes job from this podSpec. This is the default pod adapter implementation, to explicitly enable it you can specify the runtime property `druid.indexer.runner.k8s.adapter.type: overlordSingleContainer`
If you are running without a middle manager you need to also use `druid.processing.intermediaryData.storage.type=deepstore` The overlord multi container pod adapter takes the podSpec of your `Overlord` pod and creates a kubernetes job from this podSpec. It uses kubexit to manage dependency ordering between the main container that runs your druid peon and other sidecars defined in the `Overlord` pod spec. Thus if you have sidecars such as Splunk or Istio it will be able to handle them. To enable this pod adapter you can specify the runtime property `druid.indexer.runner.k8s.adapter.type: overlordMultiContainer`
Additional Configuration For the sidecar support to work for the multi container pod adapter, your entry point / command in docker must be explicitly defined your spec.
### Properties You can't have something like this:
|Property|Possible Values|Description|Default|required| Dockerfile:
|--------|---------------|-----------|-------|--------|
|`druid.indexer.runner.debugJobs`|`boolean`|Clean up K8s jobs after tasks complete.|False|No|
|`druid.indexer.runner.sidecarSupport`|`boolean`|Deprecated, specify adapter type as runtime property `druid.indexer.runner.k8s.adapter.type: overlordMultiContainer` instead. If your overlord pod has sidecars, this will attempt to start the task with the same sidecars as the overlord pod.|False|No|
|`druid.indexer.runner.primaryContainerName`|`String`|If running with sidecars, the `primaryContainerName` should be that of your druid container like `druid-overlord`.|First container in `podSpec` list|No|
|`druid.indexer.runner.kubexitImage`|`String`|Used kubexit project to help shutdown sidecars when the main pod completes. Otherwise jobs with sidecars never terminate.|karlkfi/kubexit:latest|No|
|`druid.indexer.runner.disableClientProxy`|`boolean`|Use this if you have a global http(s) proxy and you wish to bypass it.|false|No|
|`druid.indexer.runner.maxTaskDuration`|`Duration`|Max time a task is allowed to run for before getting killed|`PT4H`|No|
|`druid.indexer.runner.taskCleanupDelay`|`Duration`|How long do jobs stay around before getting reaped from K8s|`P2D`|No|
|`druid.indexer.runner.taskCleanupInterval`|`Duration`|How often to check for jobs to be reaped|`PT10M`|No|
|`druid.indexer.runner.K8sjobLaunchTimeout`|`Duration`|How long to wait to launch a K8s task before marking it as failed, on a resource constrained cluster it may take some time.|`PT1H`|No|
|`druid.indexer.runner.javaOptsArray`|`JsonArray`|java opts for the task.|`-Xmx1g`|No|
|`druid.indexer.runner.labels`|`JsonObject`|Additional labels you want to add to peon pod|`{}`|No|
|`druid.indexer.runner.annotations`|`JsonObject`|Additional annotations you want to add to peon pod|`{}`|No|
|`druid.indexer.runner.peonMonitors`|`JsonArray`|Overrides `druid.monitoring.monitors`. Use this property if you don't want to inherit monitors from the Overlord.|`[]`|No|
|`druid.indexer.runner.graceTerminationPeriodSeconds`|`Long`|Number of seconds you want to wait after a sigterm for container lifecycle hooks to complete. Keep at a smaller value if you want tasks to hold locks for shorter periods.|`PT30S` (K8s default)|No|
### Gotchas
- You must have in your role the ability to launch jobs.
- All Druid Pods belonging to one Druid cluster must be inside same kubernetes namespace.
- For the sidecar support to work, your entry point / command in docker must be explicitly defined your spec.
You can't have something like this:
Dockerfile:
``` ENTRYPOINT: ["foo.sh"] ``` ``` ENTRYPOINT: ["foo.sh"] ```
and in your sidecar specs: and in your sidecar specs:
``` container: ``` container:
name: foo name: foo
args: args:
@ -102,11 +62,11 @@ and in your sidecar specs:
- arg2 - arg2
``` ```
That will not work, because we cannot decipher what your command is, the extension needs to know it explicitly. That will not work, because we cannot decipher what your command is, the extension needs to know it explicitly.
**Even for sidecars like Istio which are dynamically created by the service mesh, this needs to happen.* **Even for sidecars like Istio which are dynamically created by the service mesh, this needs to happen.*
Instead do the following: Instead do the following:
You can keep your Dockerfile the same but you must have a sidecar spec like so: You can keep your Dockerfile the same but you must have a sidecar spec like so:
``` container: ``` container:
name: foo name: foo
command: foo.sh command: foo.sh
@ -115,33 +75,195 @@ You can keep your Dockerfile the same but you must have a sidecar spec like so:
- arg2 - arg2
``` ```
The following roles must also be accessible. An example spec could be: For both of these adapters, you can add optional labels to your K8s jobs / pods if you need them by using the following configuration:
`druid.indexer.runner.labels: '{"key":"value"}'`
Annotations are the same with:
`druid.indexer.runner.annotations: '{"key":"value"}'`
All other configurations you had for the middle manager tasks must be moved under the overlord with one caveat, you must specify javaOpts as an array:
`druid.indexer.runner.javaOptsArray`, `druid.indexer.runner.javaOpts` is no longer supported.
If you are running without a middle manager you need to also use `druid.processing.intermediaryData.storage.type=deepstore`
### Custom Template Pod Adapter
The custom template pod adapter allows you to specify a pod template file per task type for more flexibility on how to define your pods. This adapter expects a [Pod Template](https://kubernetes.io/docs/concepts/workloads/pods/#pod-templates) to be available on the overlord's file system. This pod template is used as the base of the pod spec for the Kubernetes Job. You can override things like labels, environment variables, resources, annotation, or even the base image with this template. To enable this pod adapter you can specify the runtime property `druid.indexer.runner.k8s.adapter.type: customTemplateAdapter`
The base pod template must be specified as the runtime property `druid.indexer.runner.k8s.podTemplate.base: /path/to/basePodSpec.yaml`
Task specific pod templates can be specified as the runtime property `druid.indexer.runner.k8s.podTemplate.{taskType}: /path/to/taskSpecificPodSpec.yaml` where {taskType} is the name of the task type i.e `index_parallel`
The following is an example Pod Template that uses the regular druid docker image.
```
apiVersion: "v1"
kind: "PodTemplate"
template:
metadata:
annotations:
sidecar.istio.io/proxyCPU: "512m" # to handle a injected istio sidecar
labels:
app.kubernetes.io/name: "druid-realtime-backend"
spec:
affinity: {}
containers:
- command:
- sh
- -c
- |
/peon.sh /druid/data 1
env:
- name: CUSTOM_ENV_VARIABLE
value: "hello"
image: apache/druid:{{DRUIDVERSION}}
name: main
ports:
- containerPort: 8091
name: druid-tls-port
protocol: TCP
- containerPort: 8100
name: druid-port
protocol: TCP
resources:
limits:
cpu: "1"
memory: 2400M
requests:
cpu: "1"
memory: 2400M
volumeMounts:
- mountPath: /opt/druid/conf/druid/cluster/master/coordinator-overlord # runtime props are still mounted in this location because that's where peon.sh looks for configs
name: nodetype-config-volume
readOnly: true
- mountPath: /druid/data
name: data-volume
- mountPath: /druid/deepstorage
name: deepstorage-volume
restartPolicy: "Never"
securityContext:
fsGroup: 1000
runAsGroup: 1000
runAsUser: 1000
tolerations:
- effect: NoExecute
key: node.kubernetes.io/not-ready
operator: Exists
tolerationSeconds: 300
- effect: NoExecute
key: node.kubernetes.io/unreachable
operator: Exists
tolerationSeconds: 300
volumes:
- configMap:
defaultMode: 420
name: druid-tiny-cluster-peons-config
name: nodetype-config-volume
- emptyDir: {}
name: data-volume
- emptyDir: {}
name: deepstorage-volume
```
The below runtime properties need to be passed to the Job's peon process.
``` ```
apiVersion: rbac.authorization.k8s.io/v1 druid.port=8100 (what port the peon should run on)
kind: Role druid.peon.mode=remote
druid.service=druid/peon (for metrics reporting)
druid.indexer.task.baseTaskDir=/druid/data (this should match the argument to the ./peon.sh run command in the PodTemplate)
druid.indexer.runner.type=k8s
druid.indexer.task.encapsulatedTask=true
```
Any runtime property or JVM config used by the peon process can also be passed. E.G. below is a example of a ConfigMap that can be used to generate the `nodetype-config-volume` mount in the above template.
```
kind: ConfigMap
metadata: metadata:
name: druid-cluster name: druid-tiny-cluster-peons-config
namespace: default
apiVersion: v1
data:
jvm.config: |-
-server
-XX:MaxDirectMemorySize=1000M
-Duser.timezone=UTC
-Dfile.encoding=UTF-8
-Dlog4j.debug
-Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager
-Djava.io.tmpdir=/druid/data
-Xmx1024M
-Xms1024M
log4j2.xml: |-
<?xml version="1.0" encoding="UTF-8" ?>
<Configuration status="WARN">
<Appenders>
<Console name="Console" target="SYSTEM_OUT">
<PatternLayout pattern="%d{ISO8601} %p [%t] %c - %m%n"/>
</Console>
</Appenders>
<Loggers>
<Root level="info">
<AppenderRef ref="Console"/>
</Root>
</Loggers>
</Configuration>
runtime.properties: |
druid.port=8100
druid.service=druid/peon
druid.server.http.numThreads=5
druid.indexer.task.baseTaskDir=/druid/data
druid.indexer.runner.type=k8s
druid.peon.mode=remote
druid.indexer.task.encapsulatedTask=true
```
### Properties
|Property| Possible Values | Description |Default|required|
|--------|-----------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------|--------|
|`druid.indexer.runner.debugJobs`| `boolean` | Clean up K8s jobs after tasks complete. |False|No|
|`druid.indexer.runner.sidecarSupport`| `boolean` | Deprecated, specify adapter type as runtime property `druid.indexer.runner.k8s.adapter.type: overlordMultiContainer` instead. If your overlord pod has sidecars, this will attempt to start the task with the same sidecars as the overlord pod. |False|No|
|`druid.indexer.runner.primaryContainerName`| `String` | If running with sidecars, the `primaryContainerName` should be that of your druid container like `druid-overlord`. |First container in `podSpec` list|No|
|`druid.indexer.runner.kubexitImage`| `String` | Used kubexit project to help shutdown sidecars when the main pod completes. Otherwise jobs with sidecars never terminate. |karlkfi/kubexit:latest|No|
|`druid.indexer.runner.disableClientProxy`| `boolean` | Use this if you have a global http(s) proxy and you wish to bypass it. |false|No|
|`druid.indexer.runner.maxTaskDuration`| `Duration` | Max time a task is allowed to run for before getting killed |`PT4H`|No|
|`druid.indexer.runner.taskCleanupDelay`| `Duration` | How long do jobs stay around before getting reaped from K8s |`P2D`|No|
|`druid.indexer.runner.taskCleanupInterval`| `Duration` | How often to check for jobs to be reaped |`PT10M`|No|
|`druid.indexer.runner.K8sjobLaunchTimeout`| `Duration` | How long to wait to launch a K8s task before marking it as failed, on a resource constrained cluster it may take some time. |`PT1H`|No|
|`druid.indexer.runner.javaOptsArray`| `JsonArray` | java opts for the task. |`-Xmx1g`|No|
|`druid.indexer.runner.labels`| `JsonObject` | Additional labels you want to add to peon pod |`{}`|No|
|`druid.indexer.runner.annotations`| `JsonObject` | Additional annotations you want to add to peon pod |`{}`|No|
|`druid.indexer.runner.peonMonitors`| `JsonArray` | Overrides `druid.monitoring.monitors`. Use this property if you don't want to inherit monitors from the Overlord. |`[]`|No|
|`druid.indexer.runner.graceTerminationPeriodSeconds`| `Long` | Number of seconds you want to wait after a sigterm for container lifecycle hooks to complete. Keep at a smaller value if you want tasks to hold locks for shorter periods. |`PT30S` (K8s default)|No|
|`druid.indexer.runner.capacity`| `Integer` | Number of concurrent jobs that can be sent to Kubernetes. |`2147483647`|No|
### Gotchas
- All Druid Pods belonging to one Druid cluster must be inside the same Kubernetes namespace.
- You must have a role binding for the overlord's service account that provides the needed permissions for interacting with Kubernetes. An example spec could be:
```
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
namespace: <druid-namespace>
name: druid-k8s-task-scheduler
rules: rules:
- apiGroups: - apiGroups: ["batch"]
- "" resources: ["jobs"]
- batch verbs: ["get", "watch", "list", "delete", "create"]
resources: - apiGroups: [""]
- pods resources: ["pods", "pods/log"]
- configmaps verbs: ["get", "watch", "list", "delete", "create"]
- jobs
verbs:
- '*'
--- ---
kind: RoleBinding kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1 apiVersion: rbac.authorization.k8s.io/v1
metadata: metadata:
name: druid-cluster name: druid-k8s-binding
namespace: <druid-namespace>
subjects: subjects:
- kind: ServiceAccount - kind: ServiceAccount
name: default name: <druid-overlord-k8s-service-account>
namespace: <druid-namespace>
roleRef: roleRef:
kind: Role kind: Role
name: druid-cluster name: druid-k8s-task-scheduler
apiGroup: rbac.authorization.k8s.io apiGroup: rbac.authorization.k8s.io
``` ```

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@ -0,0 +1,32 @@
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druid-kubernetes-overlord-extensions
=============
Overview
=============
The Kubernetes Task Scheduling extension allows a Druid cluster running on Kubernetes to schedule
its tasks as Kubernetes Jobs instead of sending them to workers (middle managers or indexers).
Documentation
=============
More detailed documentation about how to configure and use the extension is available [here](../../docs/development/extensions-contrib/k8s-jobs.md)