[jira] [Resolved] (AMBARI-16226) Execute topology tasks in parallel by hosts.

["Doroszlai, Attila (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AMBARI-16226?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Doroszlai, Attila resolved AMBARI-16226.
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       Resolution: Duplicate
    Fix Version/s:     (was: 3.0.0)

> Execute topology tasks in parallel by hosts.
> --------------------------------------------
>
>                 Key: AMBARI-16226
>                 URL: https://issues.apache.org/jira/browse/AMBARI-16226
>             Project: Ambari
>          Issue Type: Task
>          Components: ambari-server
>            Reporter: Sebastian Toader
>
> Currently a when a cluster is created using Blueprints PersistHostResourcesTask, RegisterWithConfigGroupTask, InstallHostTask and StartHostTask topology tasks are created for each host in this order. These tasks than are executed by a single threaded executor TopologyManager.executor as hosts are being assigned to the cluster.
> Since TopologyManager is singleton this will leads to sequential execution of topology tasks on a single thread. The execution of the each individual topology tasks involves db operations under the hood. If for any reason there is some latency introduced by the db operations (e.g. the db server is not local but a remote one is used) than this latency builds up a considerable delay if there are many hosts to execute topology tasks for.
> Executing the topology tasks in parallel will reduce the delay in this case.
> Since topology tasks for a host must be executed in order only tasks that belong to different hosts. E.g. the PersistHostResourcesTask, RegisterWithConfigGroupTask, InstallHostTask and StartHostTask topology tasks would be executed sequentially by one thread for host1 and by another thread for host2.



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