[jira] [Updated] (SLING-3993) Avoiding loops when syncing via coordinate agents

["Tommaso Teofili (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SLING-3993?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tommaso Teofili updated SLING-3993:
-----------------------------------
    Fix Version/s: Content Distribution 0.1.0

> Avoiding loops when syncing via coordinate agents
> -------------------------------------------------
>
>                 Key: SLING-3993
>                 URL: https://issues.apache.org/jira/browse/SLING-3993
>             Project: Sling
>          Issue Type: Bug
>          Components: Distribution
>            Reporter: Tommaso Teofili
>            Assignee: Tommaso Teofili
>             Fix For: Content Distribution 0.1.0
>
>
> In the case of a 'coordinate agent', sitting on 'author' instance, responsible for synchronizing 2+ 'publish' instances the simplest setup would consist of a 'queueing agent' (local exporter, no importer) sitting on each of the 'publish' instances with a trigger responsible of signaling changes of resources under a certain path so that when, for example, a resource 'bar' gets created under '/foo' the trigger will cause the creation of a package for '/foo/bar' which will be queued locally, the 'coordinate agent' will remotely fetch such a package from the queue of e.g. 'pub1' instance and remotely import it into 'pub2' instance.
> If both 'pub1' and 'pub2' have the same trigger this may result into a looping scenario when instances keep exchanging packages for the same changed content.
> Possible solutions to this can be, conceptually, based on:
> 1. identifying the source of the event that generates the replication so that events on changed resources generated by the package builder (upon package installation) are filtered and do not trigger a replication request.
> 2. filtering packages before they get transported if a same/similar package has been already sent by the target instance, keeping something a cache-like structure for the communication (in the coordinate agent).



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