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https://issues.apache.org/jira/browse/AMBARI-14749?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15112726#comment-15112726
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bhuvnesh chaudhary commented on AMBARI-14749:
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[~afernandez][~u39kun][~jaimin][~rzang][~jluniya] Please review, have a raised
a review request on OSS.
> Introduce ADD HAWQ STANDBY wizard to enable high availability in HAWQ
> ---------------------------------------------------------------------
>
> Key: AMBARI-14749
> URL: https://issues.apache.org/jira/browse/AMBARI-14749
> Project: Ambari
> Issue Type: New Feature
> Components: stacks
> Reporter: bhuvnesh chaudhary
> Assignee: bhuvnesh chaudhary
> Fix For: trunk
>
> Attachments: AMBARI-14749.patch
>
>
> This patch introduces another high availability wizard which adds HAWQ
> Standby component to the HAWQ cluster.
> Why it is required?
> Apache HAWQ database has the below components.
> - Master
> - Standby
> - Segments
> At any point of time, database connections are only accepted by the master
> and it is the single point of entry for read and write operations. In the
> background, there is a sync-up process which ensures that standby component
> is in sync with master, so that in case master goes down, HAWQ standby can be
> promoted to perform the role of master and there is minimum downtime.
> However, in order to enable High Availability operation for HAWQ, HAWQ
> standby must be configured to the cluster and required configuration changes
> must be done to ensure that HAWQ Standby is operational and in sync.
> After HAWQ Standby is added and if it has been promoted / activated to take
> the role of the HAWQ Master, the HAWQ cluster now operates in non-HA mode.
> The old HAWQ master is out of the cluster and cannot be transitioned to the
> role of Standby. In order to get back to HA state, a standby has to be added
> to the cluster.
> In this patch, the functionality to add HAWQ Standby Master has been
> introduced which performs the following functions:
> - Disable / Enable "Add HAWQ Standby" option depending on the state of the
> cluster. If HAWQ Standby is configured, this option is not visible. If HAWQ
> Standby is not configured and the cluster is not single node, the option is
> visible.
> - When the action is triggered, "Add HAWQ Standby" wizard comes into role - -
> The wizard contains of 4 pages which does a dedicated job
> - Page 1: It gives information to the user for the activities which will be
> carried out by the wizard
> - Page 2: It lets' the user chose the host on which standby should be
> installed
> - Page 3: Informs the user about the configuration changes which will take
> place based on the inputs on Page 2
> - Page 4: Below list of operations are carried.
> 1. Stop HAWQ Service
> 2. Install HAWQ Standby Component
> 3. Reconfigure HAWQ Service to add required properties
> 4. Start HAWQ service. During this step, hawq standby is initialized and
> started.
> - After the wizard completes, HAWQ standby is added to the cluster and now
> HAWQ is operational in HA mode.
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