YARN-8301. Added YARN service upgrade instructions.
Contributed by Chandni Singh
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Eric Yang
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@ -56,6 +56,4 @@ The benefits of combining these workloads are two-fold:
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* [Registry DNS](RegistryDNS.html): Deep dives into the Registry DNS internals.
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* [Examples](Examples.html): List some example service definitions (`Yarnfile`).
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* [Configurations](Configurations.html): Describes how to configure the custom services on YARN.
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* [Service Upgrade](ServiceUpgrade.html): Describes how to upgrade a YARN service which is an experimental feature.
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@ -0,0 +1,197 @@
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<!---
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License. See accompanying LICENSE file.
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-->
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# Service Upgrade (Experimental Feature - Tech Preview)
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Yarn service provides a way of upgrading/downgrading long running applications without
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shutting down the application to minimize the downtime during this process. This is
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an experimental feature which is currently not enabled by default.
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## Overview
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Upgrading a Yarn Service is a 3 steps (or 2 steps when auto-finalization of
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upgrade is chosen) process:
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1. Initiate service upgrade.\
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This step involves providing the service spec of the newer version of the service.
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Once, the service upgrade is initiated, the state of the service is changed to
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`UPGRADING`.
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2. Upgrade component instances.\
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This step involves triggering upgrade of individual component instance.
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By providing an API to upgrade at instance level, users can orchestrate upgrade
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of the entire service in any order which is relevant for the service.\
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In addition, there are APIs to upgrade multiple instances, all instances of a
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component, and all instances of multiple components.
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3. Finalize upgrade.\
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This step involves finalization of upgrade. With an explicit step to finalize the
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upgrade, users have a chance to cancel current upgrade in progress. When the
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user chose to cancel, the service will make the best effort to revert to the
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previous version.\
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\
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When the upgrade is finalized, the old service definition is
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overwritten by the new service definition and the service state changes to `STABLE`.\
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A service can be auto-finalized when the upgrade is initialized with
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`-autoFinalize` option. With auto-finalization, when all the component-instances of
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the service have been upgraded, finalization will be performed automatically by the
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service framework.\
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\
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**NOTE**: Cancel of upgrade is not implemented yet.
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## Upgrade Example
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This example shows upgrade of sleeper service. Below is the sleeper service
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definition
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```
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{
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"name": "sleeper-service",
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"components" :
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[
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{
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"name": "sleeper",
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"version": "1.0.0",
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"number_of_containers": 1,
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"launch_command": "sleep 900000",
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"resource": {
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"cpus": 1,
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"memory": "256"
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}
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}
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]
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}
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```
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Assuming, user launched an instance of sleeper service named as `my-sleeper`:
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```
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{
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"components":
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[
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{
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"configuration": {...},
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"containers":
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[
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{
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"bare_host": "0.0.0.0",
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"component_instance_name": "sleeper-0",
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"hostname": "example.local",
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"id": "container_1531508836237_0002_01_000002",
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"ip": "0.0.0.0",
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"launch_time": 1531941023675,
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"state": "READY"
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},
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{
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"bare_host": "0.0.0.0",
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"component_instance_name": "sleeper-1",
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"hostname": "example.local",
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"id": "container_1531508836237_0002_01_000003",
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"ip": "0.0.0.0",
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"launch_time": 1531941024680,
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"state": "READY"
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}
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],
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"dependencies": [],
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"launch_command": "sleep 900000",
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"name": "sleeper",
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"number_of_containers": 2,
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"quicklinks": [],
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"resource": {...},
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"restart_policy": "ALWAYS",
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"run_privileged_container": false,
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"state": "STABLE"
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}
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],
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"configuration": {...},
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"id": "application_1531508836237_0002",
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"kerberos_principal": {},
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"lifetime": -1,
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"name": "my-sleeper",
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"quicklinks": {},
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"state": "STABLE",
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"version": "1.0.0"
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}
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```
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### Enable Service Upgrade
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Below is the configuration in `yarn-site.xml` required for enabling service
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upgrade.
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```
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<property>
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<name>yarn.service.upgrade.enabled</name>
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<value>true</value>
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</property>
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```
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### Initiate Upgrade
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User can initiate upgrade using the below command:
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```
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yarn app -upgrade ${service_name} -initate ${path_to_new_service_def_file} [-autoFinalize]
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```
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e.g. To upgrade `my-sleeper` to sleep for *1200000* instead of *900000*, the user
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can upgrade the service to version 1.0.1. Below is the service definition for
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version 1.0.1 of sleeper-service:
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```
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{
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"components" :
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[
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{
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"name": "sleeper",
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"version": "1.0.1",
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"number_of_containers": 1,
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"launch_command": "sleep 1200000",
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"resource": {
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"cpus": 1,
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"memory": "256"
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}
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}
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]
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}
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```
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The command below initiates the upgrade to version 1.0.1.
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```
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yarn app -upgrade my-sleeper -initiate sleeper_v101.json
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```
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### Upgrade Instance
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User can upgrade a component instance using the below command:
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```
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yarn app -upgrade ${service_name} -instances ${comma_separated_list_of_instance_names}
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```
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e.g. The command below upgrades `sleeper-0` and `sleeper-1` instances of `my-service`:
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```
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yarn app -upgrade my-sleeper -instances sleeper-0,sleeper-1
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```
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### Upgrade Component
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User can upgrade a component, that is, all the instances of a component with
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one command:
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```
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yarn app -upgrade ${service_name} -components ${comma_separated_list_of_component_names}
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```
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e.g. The command below upgrades all the instances of `sleeper` component of `my-service`:
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```
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yarn app -ugrade my-sleeper -components sleeper
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```
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### Finalize Upgrade
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User must finalize the upgrade using the below command (since autoFinalize was not specified during initiate):
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```
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yarn app -upgrade ${service_name} -finalize
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```
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e.g. The command below finalizes the upgrade of `my-sleeper`:
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```
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yarn app -upgrade my-sleeper -finalize
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```
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