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https://issues.apache.org/jira/browse/YARN-8638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16590477#comment-16590477
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Eric Yang commented on YARN-8638:
---------------------------------

[~jlowe] {quote}
Unless I'm missing something, the whole point of a pluggable interface in this 
case is to enable runtimes that exist outside of the Apache Hadoop code base. 
There's already a separate property that controls what runtimes are allowed, so 
this plugin support is only for loading classes that aren't known by Hadoop 
when it was compiled. Limiting the classes that will be loaded to a specific 
java package prefix seems arbitrary and won't accomplish the desired effect in 
practice.{quote}

Hadoop made the scheduler pluggable in 2008, and we are still maintaining 
capacity scheduler, and fair scheduler.  This provide a long last development 
visibility for both model.  However, it also can cause security issues, if 
configuration can be override to trigger undesired behavior.  I don't know if 
we need to build more security logic here to prevent loading of arbitrary 
class, but it is worth some effort to discuss this up front. 

> Allow linux container runtimes to be pluggable
> ----------------------------------------------
>
>                 Key: YARN-8638
>                 URL: https://issues.apache.org/jira/browse/YARN-8638
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: nodemanager
>    Affects Versions: 3.2.0
>            Reporter: Craig Condit
>            Assignee: Craig Condit
>            Priority: Minor
>         Attachments: YARN-8638.001.patch, YARN-8638.002.patch
>
>
> YARN currently supports three different Linux container runtimes (default, 
> docker, and javasandbox). However, it would be relatively straightforward to 
> support arbitrary runtime implementations. This would enable easier 
> experimentation with new and emerging runtime technologies (runc, containerd, 
> etc.) without requiring a rebuild and redeployment of Hadoop. 
> This could be accomplished via a simple configuration change:
> {code:xml}
> <property>
>  <name>yarn.nodemanager.runtime.linux.allowed-runtimes</name>
>  <value>default,docker,experimental</value>
> </property>
>  
> <property>
>  <name>yarn.nodemanager.runtime.linux.experimental.class</name>
>  <value>com.somecompany.yarn.runtime.ExperimentalLinuxContainerRuntime</value>
> </property>{code}
>  
> In this example, {{yarn.nodemanager.runtime.linux.allowed-runtimes}} would 
> now allow arbitrary values. Additionally, 
> {{yarn.nodemanager.runtime.linux.\{RUNTIME_KEY}.class}} would indicate the 
> {{LinuxContainerRuntime}} implementation to instantiate. A no-argument 
> constructor should be sufficient, as {{LinuxContainerRuntime}} already 
> provides an {{initialize()}} method.
> {{DockerLinuxContainerRuntime.isDockerContainerRequested(Map<String, String> 
> env)}} and {{JavaSandboxLinuxContainerRuntime.isSandboxContainerRequested()}} 
> could be generalized to {{isRuntimeRequested(Map<String, String> env)}} and 
> added to the {{LinuxContainerRuntime}} interface. This would allow 
> {{DelegatingLinuxContainerRuntime}} to select an appropriate runtime based on 
> whether that runtime claimed ownership of the current container execution.
> For backwards compatibility, the existing values (default,docker,javasandbox) 
> would continue to be supported as-is. Under the current logic, the evaluation 
> order is javasandbox, docker, default (with default being chosen if no other 
> candidates are available). Under the new evaluation logic, pluggable runtimes 
> would be evaluated after docker and before default, in the order in which 
> they are defined in the allowed-runtimes list. This will change no behavior 
> on current clusters (as there would be no pluggable runtimes defined), and 
> preserves behavior with respect to ordering of existing runtimes.



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