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https://issues.apache.org/jira/browse/YARN-1222?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13814092#comment-13814092
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Bikas Saha commented on YARN-1222:
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bq. The root-node ACLs are per RM instance. They need to be different for it to
work. The documentation in yarn-default.xml explains this - we might have to
make it even more clear?
Clarifying it, possibly with an example would be good.
bq. The number of ACLs in the list is always bounded by
(user-configured-for-store + 1). Am I missing something?
I missed that the patch is modifying the base acl from config and not the
actual acl from the znode. The latter would have increased the count. The
former is fine. The current code is good.
Where is the shared rm-admin-acl being set such that both RMs have admin access
to the root znode? This probably works because the default is world:all. But if
that is not the case, and we are using internally generated acls, then the rm
has to give shared admin access to the other rm when it creates the root znode,
right?
bq. Do you think we should make it aware of fencing - have something like a
StoreFencedException?
I think it should be aware of when the store is not available to it because it
has been fenced out. There are/were comments in state store error handling to
differentiate between exceptions when we have such a differentiation. So we
should create a Fenced exception (look at HDFS code for an example). This way
all state store should be able to return this incident for identical handling
in the upper layers. We would like to avoid state store impls (which are
technically runtime pluggable pieces) to have to understand internal Hadoop
code patterns for HA etc.
bq. ZKRMStateStore itself is @Private @Unstable. Should we still label the
methods @Private?
At some point ZKRMStateStore will become public/stable but these methods should
remain private for testing, right?
> Make improvements in ZKRMStateStore for fencing
> -----------------------------------------------
>
> Key: YARN-1222
> URL: https://issues.apache.org/jira/browse/YARN-1222
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: Bikas Saha
> Assignee: Karthik Kambatla
> Attachments: yarn-1222-1.patch, yarn-1222-2.patch, yarn-1222-3.patch,
> yarn-1222-4.patch
>
>
> Using multi-operations for every ZK interaction.
> In every operation, automatically creating/deleting a lock znode that is the
> child of the root znode. This is to achieve fencing by modifying the
> create/delete permissions on the root znode.
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