[jira] [Commented] (IGNITE-9365) Force backups to different AWS availability zones using only Spring XML

["David Harvey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IGNITE-9365?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16590829#comment-16590829 ] 

David Harvey commented on IGNITE-9365:
--------------------------------------

I was thinking of adding new class along these lines, where the apply function will return true only if none of the node's attributes match those of any of the nodes in the list.   This would become part of the code base, but would only be used if configured as the backupAffinityFunction
 
ClusterNodeNoAttributesMatchBiPredicate implements IgniteBiPredicate<ClusterNode,List<ClusterNode>> {

 
    ClusterNodeNoAttributesMatchBiPredicate(String[] attributeNames)
    \{....}
 
For AvailabilityZones, there would be only one attribute examined, but we have some potential use cases for distributing backups across two sub-groups of an AZ.
 
Alternately, we could enhance the RendezvousAffinityFunction to allow one or more arbitrary attributes to be compared  to determine neighbors, rather  than only org.apache.ignite.macs, and to add a setting that controls whether backups should be placed on neighbors if they can't be placed anywhere else.  
 
If I have 2 backups and three availability zones (AZ), I want one copy of the data in each AZ.  If all nodes in one AZ fail, I want to be able to decide to try to get to three copies anyway, increasing the per node footprint by 50%, or to only run with one backup.     This would also give be a convoluted way to change  the number of backups of a cache dynamically:    Start the cache with a large number of backups, but don't provide a location where the backup would be allowed to run initially. 

> Force backups to different AWS availability zones using only Spring XML
> -----------------------------------------------------------------------
>
>                 Key: IGNITE-9365
>                 URL: https://issues.apache.org/jira/browse/IGNITE-9365
>             Project: Ignite
>          Issue Type: Improvement
>          Components: cache
>         Environment:  
>            Reporter: David Harvey
>            Assignee: David Harvey
>            Priority: Minor
>             Fix For: 2.7
>
>   Original Estimate: 168h
>  Remaining Estimate: 168h
>
> As a developer, I want to be able to force  cache backups each to a different "Availability Zone", when I'm running out-of-the-box Ignite, without additional Jars installed.  "Availability zone" is a AWS feature with different names for the same function by other cloud providers.  A single availability zone has the characteristic that some or all of the EC2 instances in that zone can fail together due to a single fault.   You have no control over the hosts on which the EC2 instance VMs run on in AWS, except by controlling the availability zone .  
>  
> I could write a few lines of a custom affinityBackupFilter, and configure it a RendezvousAffinityFunction, but then I have to get it deployed on all nodes in the cluster, and peer class loading will not work to this.   The code to do this should just be part of Ignite. 
>  



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