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From Harsh J <ha...@cloudera.com>
Subject Re: Fair scheduler.
Date Wed, 17 Oct 2012 07:00:54 GMT

Regular users never write into the mapred.system.dir AFAICT. That
directory, is just for the JT to use to mark its presence and to
"expose" the distributed filesystem it will be relying on.

Users write to their respective staging directories, which lies
elsewhere and is per-user.

Let me post my environment:

- mapred.system.dir (A HDFS Dir for a JT to register itself) set to
"/tmp/mapred/system". The /tmp/mapred and /tmp/mapred/system (or
whatever you configure it to) is to be owned by mapred:hadoop so that
the JT can feel free to reconfigure it.

- mapreduce.jobtracker.staging.root.dir (A HDFS dir that represents
the parent directory for user's to write their per-user job stage
files (JARs, etc.)) is set to "/user". The /user further contains each
user's home directories, owned all by them. For example:

drwxr-xr-x   - harsh    harsh 0 2012-09-27 15:51 /user/harsh

All staging files from local user 'harsh' are hence written as the
proper user under /user/harsh/.staging since that user does have
permissions to write there. For any user to access HDFS, they'd need a
home directory created on the HDFS by the admin first - and after that
things users do under their own directory, will work just fine. The JT
would not have to try to create per-user directories.

On Wed, Oct 17, 2012 at 5:22 AM, Patai Sangbutsarakum
<silvianhadoop@gmail.com> wrote:
> Thanks everyone, Seem like i hit the dead end.
> It's kind of funny when i read that jira; run it 4 time and everything
> will work.. where that magic number from..lol
> respects
> On Tue, Oct 16, 2012 at 4:12 PM, Arpit Gupta <arpit@hortonworks.com> wrote:
>> https://issues.apache.org/jira/browse/MAPREDUCE-4398
>> is the bug that Robin is referring to.
>> --
>> Arpit Gupta
>> Hortonworks Inc.
>> http://hortonworks.com/
>> On Oct 16, 2012, at 3:51 PM, "Goldstone, Robin J." <goldstone1@llnl.gov>
>> wrote:
>> This is similar to issues I ran into with permissions/ownership of
>> mapred.system.dir when using the fair scheduler.  We are instructed to set
>> the ownership of mapred.system.dir to mapred:hadoop and then when the job
>> tracker starts up (running as user mapred) it explicitly sets the
>> permissions on this directory to 700.  Meanwhile when I go to run a job as
>> a regular user, it is trying to write stuff into mapred.system.dir but it
>> can't due to the ownership/permissions that have been established.
>> Per discussion with Arpit Gupta, this is a bug with the fair scheduler and
>> it appears from your experience that there are similar issues with
>> hadoop.tmp.dir.  The whole idea of the fair scheduler is to run jobs under
>> the user's identity rather than as user mapred.  This is good from a
>> security perspective yet it seems no one bothered to account for this in
>> terms of the permissions that need to be set in the various directories to
>> enable this.
>> Until this is sorted out by the Hadoop developers, I've put my attempts to
>> use the fair scheduler on holdŠ
>> Regards,
>> Robin Goldstone, LLNL
>> On 10/16/12 3:32 PM, "Patai Sangbutsarakum" <silvianhadoop@gmail.com>
>> wrote:
>> Hi Harsh,
>> Thanks for breaking it down clearly. I would say i am successful 98%
>> from the instruction.
>> The 2% is about hadoop.tmp.dir
>> let's say i have 2 users
>> userA is a user that start hdfs and mapred
>> userB is a regular user
>> if i use default value of  hadoop.tmp.dir
>> /tmp/hadoop-${user.name}
>> I can submit job as usersA but not by usersB
>> ser=userB, access=WRITE, inode="/tmp/hadoop-userA/mapred/staging"
>> :userA:supergroup:drwxr-xr-x
>> i googled around; someone recommended to change hadoop.tmp.dir to
>> /tmp/hadoop.
>> This way it is almost a yay way; the thing is
>> if I submit as userA it will create /tmp/hadoop in local machine which
>> ownership will be userA.userA,
>> and once I tried to submit job from the same machine as userB I will
>> get  "Error creating temp dir in hadoop.tmp.dir /tmp/hadoop due to
>> Permission denied"
>> (as because /tmp/hadoop is own by userA.userA). vise versa if I delete
>> /tmp/hadoop and let the directory be created by userB, userA will not
>> be able to submit job.
>> Which is the right approach i should work with?
>> Please suggest
>> Patai
>> On Mon, Oct 15, 2012 at 3:18 PM, Harsh J <harsh@cloudera.com> wrote:
>> Hi Patai,
>> Reply inline.
>> On Tue, Oct 16, 2012 at 2:57 AM, Patai Sangbutsarakum
>> <silvianhadoop@gmail.com> wrote:
>> Thanks for input,
>> I am reading the document; i forget to mention that i am on cdh3u4.
>> That version should have the support for all of this.
>> If you point your poolname property to mapred.job.queue.name, then you
>> can leverage the Per-Queue ACLs
>> Is that mean if i plan to 3 pools of fair scheduler, i have to
>> configure 3 queues of capacity scheduler. in order to have each pool
>> can leverage Per-Queue ACL of each queue.?
>> Queues are not hard-tied into CapacityScheduler. You can have generic
>> queues in MR. And FairScheduler can bind its Pool concept into the
>> Queue configuration.
>> All you need to do is the following:
>> 1. Map FairScheduler pool name to reuse queue names itself:
>> mapred.fairscheduler.poolnameproperty set to 'mapred.job.queue.name'
>> 2. Define your required queues:
>> mapred.job.queues set to "default,foo,bar" for example, for 3 queues:
>> default, foo and bar.
>> 3. Define Submit ACLs for each Queue:
>> mapred.queue.default.acl-submit-job set to "patai,foobar users,adm"
>> (usernames groupnames)
>> mapred.queue.foo.acl-submit-job set to "spam eggs"
>> Likewise for remaining queues, as you need itŠ
>> 4. Enable ACLs and restart JT.
>> mapred.acls.enabled set to "true"
>> 5. Users then use the right API to set queue names before submitting
>> jobs, or use -Dmapred.job.queue.name=value via CLI (if using Tool):
>> http://hadoop.apache.org/docs/stable/api/org/apache/hadoop/mapred/JobConf
>> .html#setQueueName(java.lang.String)
>> 6. Done.
>> Let us know if this works!
>> --
>> Harsh J

Harsh J

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