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https://issues.apache.org/jira/browse/YARN-7217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16211440#comment-16211440
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Jian He commented on YARN-7217:
-------------------------------
In description:
bq. The update service API provides multiple functions:
bq. Stopping a service.
bq. Start a service.
bq. Increase or decrease number of containers.
I meant there are only stop and start in current code, Increase or decrease
is already removed. anyway, I can check the code what it does exactly.
> Improve API service usability for updating service spec and state
> -----------------------------------------------------------------
>
> Key: YARN-7217
> URL: https://issues.apache.org/jira/browse/YARN-7217
> Project: Hadoop YARN
> Issue Type: Task
> Components: api, applications
> Reporter: Eric Yang
> Assignee: Eric Yang
> Attachments: YARN-7217.yarn-native-services.001.patch,
> YARN-7217.yarn-native-services.002.patch,
> YARN-7217.yarn-native-services.003.patch,
> YARN-7217.yarn-native-services.004.patch
>
>
> API service for deploy, and manage YARN services have several limitations.
> The update service API provides multiple functions:
> # Stopping a service.
> # Start a service.
> # Increase or decrease number of containers.
> The overloading is buggy depending on how the configuration should be applied.
> Scenario 1
> A user retrieves Service object from getService call, and the Service object
> contains state: STARTED. The user would like to increase number of
> containers for the deployed service. The JSON has been updated to increase
> container count. The PUT method does not actually increase container count.
> Scenario 2
> A user retrieves Service object from getService call, and the Service object
> contains state: STOPPED. The user would like to make a environment
> configuration change. The configuration does not get updated after PUT
> method.
> This is possible to address by rearranging the logic of START/STOP after
> configuration update. However, there are other potential combinations that
> can break PUT method. For example, user like to make configuration changes,
> but not yet restart the service until a later time.
> The alternative is to separate the PUT method into PUT method for
> configuration vs status. This increase the number of action that can be
> performed. New API could look like:
> {code}
> @PUT
> /ws/v1/services/[service_name]/spec
> Request Data:
> {
> "name":"[service_name]",
> "number_of_containers": 5
> }
> {code}
> {code}
> @PUT
> /ws/v1/services/[service_name]/state
> Request data:
> {
> "name": "[service_name]",
> "state": "STOPPED|STARTED"
> }
> {code}
> Scenario 3
> There is no API to list all deployed applications by the same user.
> Scenario 4
> Desired state (spec) and current state are represented by the same Service
> object. There is no easy way to identify "state" is desired state to reach
> or, the current state of the service. It would be nice to have ability to
> retrieve both desired state, and current state with separated entry points.
> By implementing /spec and /state, it can resolve this problem.
> Scenario 5
> List all services deploy by the same user can trigger a directory listing
> operation on namenode if hdfs is used as storage for metadata. When hundred
> of users use Service UI to view or deploy applications, this will trigger
> denial of services attack on namenode. The sparse small metadata files also
> reduce efficiency of Namenode memory usage. Hence, a cache layer for storing
> service metadata would be nice.
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