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Flume >> mail # user >> hdfs.idleTimeout ,what's it used for ?


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Bhaskar V. Karambelkar 2013-01-17, 20:07
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Connor Woodson 2013-01-17, 20:29
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Bhaskar V. Karambelkar 2013-01-17, 21:38
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Juhani Connolly 2013-01-18, 02:08
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Mohit Anchlia 2013-01-18, 02:17
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Connor Woodson 2013-01-18, 02:19
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Connor Woodson 2013-01-18, 02:20
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Connor Woodson 2013-01-18, 02:23
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Juhani Connolly 2013-01-18, 02:46
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Connor Woodson 2013-01-18, 03:24
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Juhani Connolly 2013-01-18, 03:39
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Connor Woodson 2013-01-18, 04:18
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Re: hdfs.idleTimeout ,what's it used for ?


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On Jan 17, 2013, at 6:46 PM, Juhani Connolly <[EMAIL PROTECTED]> wrote:

> It seemed neater at the time. It's only an issue because rollInterval doesn't remove the entry in sfWriters. We could change it so that close doesn't cancel it, and have it check whether or not the writer is already closed, but that'd be kind of ugly.
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> @Mohit:
>
> When flume dies unexpectedly the .tmp file remains. When it restarts there is some logic in HDFS sink to recover it(and continue writing from there). I'm not actually sure of the specifics. You may want to try and just kill -9 a running flume process on a test machine and then start it up, look at the logs and see what happens with the output.

Does it also work when there is a long delay before flume gets started? We are bucketing by the hr so if start occurs in the next hour but flume actually died in previous hr and had  .tmp then does it still cleanup on restart
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> If flume dies cleanly the file is properly closed.
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> On 01/18/2013 11:23 AM, Connor Woodson wrote:
>> And @ my aside: I hadn't realized that the idleTimeout is canceled by the rollInterval occurring. That's annoying. So setting a lower idleTimeout, and drastically decreasing maxOpenFiles to at most 2 * possible open files, is probably necessary.
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>> On Thu, Jan 17, 2013 at 6:20 PM, Connor Woodson <[EMAIL PROTECTED]> wrote:
>>> @Mohit:
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>>> For the HDFS Sink, the tmp files are placed based on the hadoop.tmp.dir property. The default location is /tmp/hadoop-${user.name} To change this you can add -Dhadoop.tmp.dir=<path>                 to your Flume command line call, or you can specify the property in the core-site.xml of wherever your                 HADOOP_HOME environment variable points to.
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>>> - Connor
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>>> On Thu, Jan 17, 2013 at 6:19 PM, Connor Woodson <[EMAIL PROTECTED]> wrote:
>>>> Whether idleTimeout is lower or higher than rollInterval is a preference; set it before, and assume you get one message right on the turn of the hour, then you will have some part of that hour without any bucket writers; but if you get another message at the end of the hour, you will end up with two files instead of one. Set it idleTimeout to be longer and you will get just one file, but also (at worst case) you will have twice as many bucketwriters open; so it all depends on how many files you want/how much memory you have to spare.
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>>>> - Connor
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>>>> An aside:
>>>> bucketwriters, after being closed by rollInterval, aren't really a memory leak; they just are very rarely useful to keep around (your path could rely on hostname, and you could use a rollinterval, and then those bucketwriters will still remain useful). And they will get removed eventually; by default after you've created your 5001st bucketwriter, the first (or whichever was used longest ago) will be removed.
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>>>> And I don't think that's the cause behind 1850 as he did have an idleTimeout set at 15 minutes.
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>>>> On Thu, Jan 17, 2013 at 6:08 PM, Juhani Connolly <[EMAIL PROTECTED]> wrote:
>>>>> It's also useful if you want files to get promptly closed and renamed from the .tmp or whatever.
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>>>>> We use it with something like 30seconds setting(we have a constant stream of data) and hourly bucketing.
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>>>>> There is also the issue that files closed by rollInterval are never removed from the internal linkedList so it actually causes a small memory leak(which can get big in the long term if you have a lot of files and hourly renames). I believe this is what is causing the OOM Mohit is getting in FLUME-1850
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>>>>> So I personally would recommend using it(with a setting that will close files before rollInterval does).
>>>>>
>>>>>
>>>>> On 01/18/2013 06:38 AM, Bhaskar V. Karambelkar wrote:
>>>>>> Ah I see. Again something useful to have in the flume user guide.
>>>>>>
>>>>>> On Thu, Jan 17, 2013 at 3:29 PM, Connor Woodson <[EMAIL PROTECTED]> wrote:
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Juhani Connolly 2013-01-18, 06:37
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Juhani Connolly 2013-01-18, 02:39
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Connor Woodson 2013-01-18, 02:42