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From "Dmitry Lysnichenko (JIRA)" <>
Subject [jira] [Commented] (AMBARI-4504) role_command_order is not inherited from the parent stack
Date Mon, 03 Feb 2014 15:04:11 GMT


Dmitry Lysnichenko commented on AMBARI-4504:

[~mahadev]/[~sumitmohanty], can you please take a look on implementation proposal?

> role_command_order is not inherited from the parent stack
> ---------------------------------------------------------
>                 Key: AMBARI-4504
>                 URL:
>             Project: Ambari
>          Issue Type: Task
>          Components: controller, test
>    Affects Versions: 1.5.0
>            Reporter: Dmitry Lysnichenko
>            Assignee: Dmitry Lysnichenko
>             Fix For: 1.5.0
> h1. Implementation proposal
> The most common use case for stack extension is adding new services or slightly modifying
existing ones. So typically child's RCO file should look like a diff ("What dependencies should
we add to parent's RCO to support newly added services?"). For  more complex situations (when
changes that are introduced by child stack fundamentally change RCO), it makes sense to redefine
a complete RCO file instead of inheritance. That's why I propose to keep RCO file syntax simple
and don't implement support of deleting/modifying specific dependency or dependency group.

> We will support two options(policies) for stack extension:
> - extend parent's RCO, appending dependencies specified at child's RCO to corresponding
groups of parent's RCO (default). For every dependency group, parent's set of dependencies
and child's set of dependencies are merged.
> - completely override (replace) parent's RCO by child's RCO file.
> Policy selection is done at stack metainfo.xml.
> {code}
> <metainfo>
>   <versions>
>     <active>true</active>
>   </versions>
>   <extends>2.0.5</extends>
>   <rco-policy>append</rco-policy>
>   <!-- or -->
>   <rco-policy>replace</rco-policy>
> </metainfo>
> {code}
> If role_command_order.json file is absent at stack, parent's file is used.
> Also, for every role_command_order.json file at inherited stacks, I'll add a comment
> {code}
> This file appends role command order dependencies to ones defined at parent stack. To
change this behaviour, please refer to documentation about rco-policy element of a stack metainfo.xml
> {code}
> Also, in debug mode, an effective RCO will be printed to log to simplify troubleshooting.

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