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From "Stefan Egli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-3935) SharedDataStore - Allow unique repository ID to be specified by config
Date Mon, 01 Feb 2016 10:49:39 GMT

    [ https://issues.apache.org/jira/browse/OAK-3935?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15126096#comment-15126096
] 

Stefan Egli commented on OAK-3935:
----------------------------------

bq. Can we use sling's cluster id here, which will make it semantically similar?
I'm assuming you're referring to discovery API's {{ClusterView.getId()}} ?
The way this is solved in discovery.impl (for all cases) and discovery.oak (for tarmk) is
by storing a uuid under /var/discovery/... - thus cloning a repository requires deleting this
id in the cloned repo too (which is do-able as it is not a hidden path/property). (For mongoMk
this is stored in the settings collection and there's currently no easy way to delete it should
someone clone a mongo repo. But that is less likely/frequent than cloning a tarMk repo IMO).

bq. Can we use sling's cluster id here
So I guess yes, it can be used. With the restrictions that are applicable, such as: the ID
is not always available, especially not during startup, at which point discovery is still
busy determining a valid view. It is also not available during topology changes - but in a
tarMk there's no topology changes relating to the local cluster (as it is by definition always
1 instance). So basically once the initial topology is provided via {{TOPOLOGY_INIT}} (or
via {{DiscoveryService.getTopology().isCurrent()==true}}) any subsequent event can 'in theory'
be ignored wrt the local cluster's id (for segment that is).

So conceptually this can be reused yes. It would of course introduce a(nother) dependency
from Oak to Sling - but if that's acceptable and optional, there's nothing that prevents this.


> SharedDataStore - Allow unique repository ID to be specified by config 
> -----------------------------------------------------------------------
>
>                 Key: OAK-3935
>                 URL: https://issues.apache.org/jira/browse/OAK-3935
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: blob, segmentmk
>            Reporter: Amit Jain
>            Assignee: Amit Jain
>              Labels: resilience
>             Fix For: 1.2.11, 1.3.15
>
>         Attachments: OAK-3935-sling-settings.patch
>
>
> For GC in a shared DataStore, a unique repository Id is currently saved in a hidden path
in the node store on startup and registered in the DataStore.
> This will cause problems where the publish environments are cloned and share a datastore.
> There should be an option to specify a unique id in the config when setting up the node
store.



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