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https://issues.apache.org/jira/browse/AMBARI-24537?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Hurley resolved AMBARI-24537.
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Resolution: Fixed
> Use Mpack Instance Manager To Switch Component Instance Version on Upgrade
> --------------------------------------------------------------------------
>
> Key: AMBARI-24537
> URL: https://issues.apache.org/jira/browse/AMBARI-24537
> Project: Ambari
> Issue Type: Task
> Affects Versions: 3.0.0
> Reporter: Jonathan Hurley
> Assignee: Jonathan Hurley
> Priority: Blocker
> Labels: pull-request-available
> Fix For: 3.0.0
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> Mpacks will not continue use the {{stack-select}} tools which have been used
> by various stacks over the past few years. Previously, each stack shipped a
> tool which would manipulate the symlinks on the file system in order to both
> report versions for components and to change versions during an upgrade.
> The following pieces were required for this old framework:
> - A file, such as {{stack_packages.json}} which provided a mapping between
> Ambari's component name and the symlink name on the file system.
> - Each component's Python file would need code which flips the version before
> restarting during an upgrade:
> {code}
> def pre_upgrade_restart(self, env, upgrade_type=None):
> if params.version and check_stack_feature(StackFeature.ROLLING_UPGRADE,
> format_stack_version(params.version)):
> stack_select.select_packages(params.version)
> {code}
> Mpacks v2 will instead use the mpack instance manager to change the pointer
> on the file system:
> {noformat}
> /usr/hwx/mpacks
> └── hdpcore
> ├── 1.0.0-b575
> │ ├── zookeeper_client -> /usr/hwx/modules/zookeeper_clients/3.4.0.0-b42
> │ └── zookeeper_server -> /usr/hwx/modules/zookeeper/3.4.0.0-b42
> └── 1.0.0-b580
> ├── zookeeper_client -> /usr/hwx/modules/zookeeper_clients/3.4.0.0-b43
> └── zookeeper_server -> /usr/hwx/modules/zookeeper_clients/3.4.0.0-b43
> {noformat}
> {noformat}
> /usr/hwx/instances
> └── hdpcore
> └── HDPCORE
> └── default
> ├── zookeeper
> │ └── zookeeper_server
> │ └── ZK-1
> │ ├── current ->
> /usr/hwx/mpacks/hdpcore/1.0.0-b575/zookeeper_server
> └── zookeeper_client
> ├── current ->
> /usr/hwx/mpacks/hdpcore/1.0.0-b575/zookeeper_client
> {noformat}
> For each instance of a component, there is a {{current}} pointer which
> references the mpack (and indirectly) the module version. However, Ambari
> knows all of this information up front since it's all based on metadata
> contained with the {{mpack.json}}. Therefore, it is possible for Ambari to do
> all of this version linking inside of its own framework during the upgrade.
> The individual Python scripts will no longer have to perform these actions.
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