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https://issues.apache.org/jira/browse/YARN-9834?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16930716#comment-16930716
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Eric Yang commented on YARN-9834:
---------------------------------
[~shanyu] SSSD does not mirror all users, and it only caches users on demand
during per user lookup. Hence, it is very efficient. Winbind does have the
limitation that this issue tries to address.
Can we change the config from:
{code}
yarn.nodemanager.linux-container-executor.secure-mode.use-local-user=false
{code}
to
{code}
yarn.nodemanager.linux-container-executor.secure-mode.use-pool-user=false
{code}
Use-local-user can be misleading for some users who would like to use
/etc/passwd users, but get confused by the meaning of the config name. Thanks
> Allow using a pool of local users to run Yarn Secure Container in secure mode
> -----------------------------------------------------------------------------
>
> Key: YARN-9834
> URL: https://issues.apache.org/jira/browse/YARN-9834
> Project: Hadoop YARN
> Issue Type: Bug
> Components: nodemanager
> Affects Versions: 3.1.2
> Reporter: shanyu zhao
> Assignee: shanyu zhao
> Priority: Major
>
> Yarn Secure Container in secure mode allows separation of different user's
> local files and container processes running on the same node manager. This
> depends on an out of band service such as SSSD/Winbind to sync all domain
> users to local machine.
> SSSD/Winbind user sync has lots of overhead, especially for large
> corporations. Also if running Yarn inside Kubernetes cluster (meaning node
> managers running inside Docker container), it doesn't make sense for each
> container to sync a whole copy of domain users.
> We should allow a new configuration to Yarn, such that we can pre-create a
> pool of users on each machine/Docker container. And at runtime, Yarn
> allocates a local user to the domain user that submits the application. When
> all containers of that user and all files belonging to that user are deleted,
> we can release the allocation and allow other users to use the same local
> user to run their Yarn containers.
> h2. Design
> We propose to add these new configurations:
> {code:java}
> yarn.nodemanager.linux-container-executor.secure-mode.use-local-user,
> defaults to false
> yarn.nodemanager.linux-container-executor.secure-mode.local-user-prefix,
> defaults to "user"{code}
> By default this feature is turned off. If we enable it, with
> local-user-prefix set to "user", then we expect there are pre-created local
> users user0 - usern, where n equals to:
> {code:java}
> yarn.nodemanager.resource.cpu-vcores {code}
> We can use an in-memory allocator to keep the domain user to local user
> mapping. When to add the mapping and when to remove it?
> In node manager, ApplicationImpl implements the state machine for a Yarn app
> life cycle, only if the app has at least 1 container running on that node
> manager. We can hook up the code to add the mapping during application
> initialization.
> For removing the mapping, we need to wait for 3 things:
> 1) All applications of the same user is completed;
> 2) All log handling of the applications (log aggregation or non-aggregated
> handling) is done;
> 3) All pending FileDeletionTask that use the user's identity is finished.
> If all of our local users in the pool are allocated, we'll return
> "nonexistuser" as runas user, this will cause the container to fail to
> execute and Yarn will relaunch it in other nodes.
> h2. Limitations
> 1) This feature does not support PRIVATE visibility type of resource
> allocation. Because PRIVATE type of resources are potentially cached in the
> node manager for a very long time, supporting it will be a security problem
> that a user might be able to peek into previous user's PRIVATE resources. We
> can modify code to treat all PRIVATE type of resource as APPLICATION type.
> 2) It is recommended to enable DominantResourceCalculator so that no more
> than "cpu-vcores" number of concurrent containers running on a node manager:
> {code:java}
> yarn.scheduler.capacity.resource-calculator
> = org.apache.hadoop.yarn.util.resource.DominantResourceCalculator {code}
> 3) Currently this feature does not work with Yarn Node Manager recovery. This
> is because the mappings are kept in memory, it cannot be recovered after node
> manager restart.
>
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