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From "JiankunLiu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-2381) CLONE - Yarn Scheduler Load Simulator
Date Mon, 04 Aug 2014 08:58:11 GMT
JiankunLiu created YARN-2381:
--------------------------------

             Summary: CLONE - Yarn Scheduler Load Simulator
                 Key: YARN-2381
                 URL: https://issues.apache.org/jira/browse/YARN-2381
             Project: Hadoop YARN
          Issue Type: New Feature
          Components: scheduler
            Reporter: JiankunLiu
            Assignee: Wei Yan
             Fix For: 2.3.0


The Yarn Scheduler is a fertile area of interest with different implementations, e.g., Fifo,
Capacity and Fair  schedulers. Meanwhile, several optimizations are also made to improve scheduler
performance for different scenarios and workload. Each scheduler algorithm has its own set
of features, and drives scheduling decisions by many factors, such as fairness, capacity guarantee,
resource availability, etc. It is very important to evaluate a scheduler algorithm very well
before we deploy it in a production cluster. Unfortunately, currently it is non-trivial to
evaluate a scheduling algorithm. Evaluating in a real cluster is always time and cost consuming,
and it is also very hard to find a large-enough cluster. Hence, a simulator which can predict
how well a scheduler algorithm for some specific workload would be quite useful.

We want to build a Scheduler Load Simulator to simulate large-scale Yarn clusters and application
loads in a single machine. This would be invaluable in furthering Yarn by providing a tool
for researchers and developers to prototype new scheduler features and predict their behavior
and performance with reasonable amount of confidence, there-by aiding rapid innovation.

The simulator will exercise the real Yarn ResourceManager removing the network factor by simulating
NodeManagers and ApplicationMasters via handling and dispatching NM/AMs heartbeat events from
within the same JVM.

To keep tracking of scheduler behavior and performance, a scheduler wrapper will wrap the
real scheduler.

The simulator will produce real time metrics while executing, including:

* Resource usages for whole cluster and each queue, which can be utilized to configure cluster
and queue's capacity.
* The detailed application execution trace (recorded in relation to simulated time), which
can be analyzed to understand/validate the  scheduler behavior (individual jobs turn around
time, throughput, fairness, capacity guarantee, etc).
* Several key metrics of scheduler algorithm, such as time cost of each scheduler operation
(allocate, handle, etc), which can be utilized by Hadoop developers to find the code spots
and scalability limits.

The simulator will provide real time charts showing the behavior of the scheduler and its
performance.

A short demo is available http://www.youtube.com/watch?v=6thLi8q0qLE, showing how to use simulator
to simulate Fair Scheduler and Capacity Scheduler.



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