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https://issues.apache.org/jira/browse/HADOOP-4522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12647512#action_12647512
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Vivek Ratan commented on HADOOP-4522:
-------------------------------------
Adding to Dhruba's comments.
I suppose it's up to the component to decide what to re-read and what not to?
For example, do we want the QueueManager to re-read the list of all queues in
the system so that it can dynamically add new queues or delete existing queues?
probably not, as it will affect jobs in current queues (you can't 'delete' a
queue if it has jobs running or waiting). No matter what we do, components that
depend on the QueueManager need to know that. The CapacityScheduler, for
example, needs to know whether new queues are accepted, so that it may, in
turn, read (or not read) scheduling information related to the new queues.
I think that having the system re-read its configuration through a single call
is OK, but we may need to make it explicit, in documentation, what config
values are re-read and what are ignored. We'd also want admins to be explicitly
aware that ALL config files are re-read. OTOH, you way want to break down
config information into sub-sections (config for scheduling, for JT, etc), and
provide one or more sub-sections as parameters in the call, but this might get
messy.
Beyond scheduling, has there been a need to have the system re-read its
configuration?
> Capacity Scheduler needs to re-read its configuration
> -----------------------------------------------------
>
> Key: HADOOP-4522
> URL: https://issues.apache.org/jira/browse/HADOOP-4522
> Project: Hadoop Core
> Issue Type: New Feature
> Reporter: Vivek Ratan
>
> An external application (an Ops script, or some CLI-based tool) can change
> the configuration of the Capacity Scheduler (change the capacities of various
> queues, for example) by updating its config file. This application then needs
> to tell the Capacity Scheduler that its config has changed, which causes the
> Scheduler to re-read its configuration. It's possible that the Capacity
> Scheduler may need to interact with external applications in other similar
> ways.
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