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From "Naganarasimha G R (Naga)" <garlanaganarasi...@huawei.com>
Subject FW: Is it valid to use userLimit in calculating maxApplicationsPerUser ?
Date Thu, 16 Jul 2015 07:53:08 GMT
Hi Folks ,
Came across one scenario where in maxApplications @ cluster level(2 node) was set to a low
value like 10 and based on capacity configuration for a particular queue it was coming to
2 as value, but further while calculating maxApplicationsPerUser formula used is :

maxApplicationsPerUser = (int)(maxApplications * (userLimit / 100.0f) * userLimitFactor);

but the definition of userLimit  in the documentation is :
Each queue enforces a limit on the percentage of resources allocated to a user at any given
time, if there is demand for resources. The user limit can vary between a minimum and maximum
value. The the former (the minimum value) is set to this property value and the latter (the
maximum value) depends on the number of users who have submitted applications. For e.g., suppose
the value of this property is 25. If two users have submitted applications to a queue, no
single user can use more than 50% of the queue resources. If a third user submits an application,
no single user can use more than 33% of the queue resources. With 4 or more users, no user
can use more than 25% of the queues resources. A value of 100 implies no user limits are imposed.
The default is 100. Value is specified as a integer.

So was wondering how a minimum limit is made used in a formula to calculate max applications
for a user, suppose i set "yarn.scheduler.capacity.<queue-path>.minimum-user-limit-percent"
to 20  assuming at least 20% of queue at the minimum is available for a queue but based on
the formula maxApplicationsPerUser  is getting set to zero.
According to the definition of the property max is based on the current no. of active users,
so i feel this formula is wrong.
P.S. userLimitFactor was configured as default 1, but what i am wondering is whether its valid
to use it in combination with userlimit to find max apps per user.

Please correct me if my understanding is wrong? if its a bug would like to raise and solve
it .

+ Naga

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