Arun Suresh created YARN-8849:
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Summary: DynoYARN: A simulation and testing infrastructure for
YARN clusters
Key: YARN-8849
URL: https://issues.apache.org/jira/browse/YARN-8849
Project: Hadoop YARN
Issue Type: New Feature
Reporter: Arun Suresh
Traditionally, YARN workload simulation is performed using SLS (Scheduler Load
Simulator) which is packaged with YARN. It Essentially, starts a full fledged
*ResourceManager*, but runs simulators for the *NodeManager* and the
*ApplicationMaster* Containers. These simulators are lightweight and run in a
threadpool. The NM simulators do not open any external ports and send
(in-process) heartbeats to the ResourceManager.
There are a couple of drawbacks with using the SLS:
* It might be difficult to simulate really large clusters without having access
to a very beefy box - since the NMs are launched as tasks in a threadpool, and
each NM has to send periodic heartbeats to the RM.
* Certain features (like YARN-1011) requires changes to the NodeManager -
aspects such as queuing and selectively killing containers have to be
incorporate into the existing NM Simulator which might make the simulator a bit
heavy weight - there is a need for locking and synchronization.
* Since the NM and AM are simulations, only the Scheduler is faithfully tested
- it does not really perform an end-2-end test of a cluster.
Therefore, drawing inspiration from
[Dynamometer|https://github.com/linkedin/dynamometer], we propose a framework
for YARN deployable YARN cluster - *DynoYARN* - for testing, with the following
features:
* The NM already has hooks to plug-in custom *ContainerExecutor* and
*NodeResourceMonitor*. If we can plug-in a custom *ContainersMonitorImpl*'s
Monitoring thread (and other modules like the LocalizationService), We can
probably inject an Executor that does not actually launch containers and a Node
and Container resource monitor that reports synthetic pre-specified Utilization
metrics back to the RM.
* Since we are launching fake containers, we cannot run normal AM containers.
We can therefore, use *Unmanaged AM*'s to launch synthetic jobs.
Essentially, a test workflow would look like this:
* Launch a DynoYARN cluster.
* Use the Unmanaged AM feature to directly negotiate with the DynaYARN Resource
Manager for container tokens.
* Use the container tokens from the RM to directly ask the DynoYARN Node
Managers to start fake containers.
* The DynoYARN NodeManagers will start the fake containers and report to the
DynoYARN Resource Manager synthetically generated resource utilization for the
containers (which will be injected via the *ContainerLaunchContext* and parsed
by the plugged-in Container Executor).
* The Scheduler will use the utilization report to schedule containers - we
will be able to test allocation of {{Opportunistic}} containers based on
resource utilization.
* Since the DynoYARN Node Managers run the actual code paths, all preemption
and queuing logic will be faithfully executed.
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