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From Hari Shreedharan <hshreedha...@cloudera.com>
Subject Re: File Channel Backup Checkpoints are I/O Intensive
Date Thu, 03 Jul 2014 03:47:46 GMT
Thanks a lot. I will take a look at this tomorrow or early next week.


On Wed, Jul 2, 2014 at 5:29 PM, Abraham Fine <abe@brightroll.com> wrote:

> Hari-
>
> I added the new tests and created a new revision to my patch.
>
>
> https://issues.apache.org/jira/secure/attachment/12653728/compress_backup_checkpoint_new_tests.patch
>
> Thanks,
> Abe
>
> --
> Abraham Fine | Software Engineer
> (516) 567-2535
> BrightRoll, Inc. | Smart Video Advertising | www.brightroll.com
>
>
> On Wed, Jul 2, 2014 at 4:32 PM, Hari Shreedharan <
> hshreedharan@cloudera.com> wrote:
>
>> Hi Abraham,
>>
>> In general, the patch looks good. Can you add a couple of tests -
>> * Original checkpoint is uncompressed, config changes to compress
>> checkpoint - does the file channel restart from original checkpoint? are
>> new checkpoints compressed?
>> * Compressed checkpoint, config changes to not compress checkpoint - does
>> channel start up? are new checkpoints uncompressed?
>>
>>
>> Hari
>>
>>
>>  On Wed, Jul 2, 2014 at 3:06 PM, Abraham Fine <abe@brightroll.com> wrote:
>>
>>> Hi Brock and Hari-
>>>
>>> I was just wondering if either of you had a chance to take a look at the
>>> patch and if there is anything I can do to improve it.
>>>
>>> Thanks,
>>> Abe
>>>
>>> --
>>> Abraham Fine | Software Engineer
>>> (516) 567-2535
>>> BrightRoll, Inc. | Smart Video Advertising | www.brightroll.com
>>>
>>>
>>> On Wed, Jun 11, 2014 at 6:48 PM, Brock Noland <brock@cloudera.com>
>>> wrote:
>>>
>>>> This is a great suggestion Abraham!
>>>>
>>>>
>>>> On Wed, Jun 11, 2014 at 5:39 PM, Hari Shreedharan <
>>>> hshreedharan@cloudera.com> wrote:
>>>>
>>>>>  Thanks. I will review it :)
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Hari
>>>>>
>>>>> On Wednesday, June 11, 2014 at 5:00 PM, Abraham Fine wrote:
>>>>>
>>>>> I went ahead and created a JIRA and patch:
>>>>> https://issues.apache.org/jira/browse/FLUME-2401
>>>>>
>>>>> The option is configurable with:
>>>>> agentX.channels.ch1.compressBackupCheckpoint = true
>>>>>
>>>>> As per your recommendation, I used snappy-java. I also considered the
>>>>> snappy and lz4 implementations in Hadoop IO but noticed that the
>>>>> Hadoop IO dependency was removed in
>>>>> https://issues.apache.org/jira/browse/FLUME-1285
>>>>>
>>>>> Thanks,
>>>>> Abe
>>>>> --
>>>>> Abraham Fine | Software Engineer
>>>>> (516) 567-2535
>>>>> BrightRoll, Inc. | Smart Video Advertising | www.brightroll.com
>>>>>
>>>>>
>>>>> On Mon, Jun 9, 2014 at 4:01 PM, Hari Shreedharan
>>>>> <hshreedharan@cloudera.com> wrote:
>>>>>
>>>>> Hi Abraham,
>>>>>
>>>>> Compressing the backup checkpoint is very possible. Since the backup
is
>>>>> rarely read (only if the original one is corrupt on restarts), is it
>>>>> used.
>>>>> So I think compressing it using something like Snappy would make sense
>>>>> (GZIP
>>>>> might hit performance). Can you try using snappy-java and see if that
>>>>> gives
>>>>> good perf and reasonable compression?
>>>>>
>>>>> Patches are always welcome. I’d be glad to review and commit it. I
>>>>> would
>>>>> suggest making the compression optional via configuration so that
>>>>> anyone
>>>>> with smaller channels don’t end up using CPU for not much gain.
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Hari
>>>>>
>>>>> On Monday, June 9, 2014 at 3:56 PM, Abraham Fine wrote:
>>>>>
>>>>> Hello-
>>>>>
>>>>> We are using Flume 1.4 with File Channel configured to use a very
>>>>> large capacity. We keep the checkpoint and backup checkpoint on
>>>>> separate disks.
>>>>>
>>>>> Normally the file channel is mostly empty (<<1% of capacity). For
the
>>>>> checkpoint the disk I/O seems to be very reasonable due to the usage
>>>>> of a MappedByteBuffer.
>>>>>
>>>>> On the other hand, the backup checkpoint seems to be written to disk
>>>>> in its entirety over and over again, resulting in very high disk
>>>>> utilization.
>>>>>
>>>>> I noticed that, because the checkpoint file is mostly empty, it is
>>>>> very compressible. I was able to GZIP our checkpoint from 381M to
>>>>> 386K. I was wondering if it would be possible to always compress the
>>>>> backup checkpoint before writing it to disk.
>>>>>
>>>>> I would be happy to work on a patch to implement this functionality if
>>>>> there is interest.
>>>>>
>>>>> Thanks in Advance,
>>>>>
>>>>> --
>>>>> Abraham Fine | Software Engineer
>>>>> (516) 567-2535
>>>>> BrightRoll, Inc. | Smart Video Advertising | www.brightroll.com
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>

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