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.
@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.
If flume dies cleanly the file is properly closed.
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.
On Thu, Jan 17, 2013 at 6:20 PM, Connor Woodson
<[email protected] <mailto:[email protected]>> wrote:
@Mohit:
For the HDFS Sink, the tmp files are placed based on the
hadoop.tmp.dir property. The default location is
/tmp/hadoop-${user.name <http://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.
- Connor
On Thu, Jan 17, 2013 at 6:19 PM, Connor Woodson
<[email protected] <mailto:[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.
- Connor
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.
And I don't think that's the cause behind 1850 as he did have
an idleTimeout set at 15 minutes.
On Thu, Jan 17, 2013 at 6:08 PM, Juhani Connolly
<[email protected]
<mailto:[email protected]>> wrote:
It's also useful if you want files to get promptly closed
and renamed from the .tmp or whatever.
We use it with something like 30seconds setting(we have a
constant stream of data) and hourly bucketing.
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
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]
<mailto:[email protected]>> wrote:
the rollInterval will still cause the last 01-17
file to be closed
eventually. The way the HDFS sink works with the
different files is each
unique path is specified by a different
BucketWriter object. The sink can
hold as many objects as specified by
hdfs.maxOpenWorkers (default: 5000),
and bucketwriters are only removed when you create
the 5001th writer (5001th
unique path). However, generally once a writer is
closed it is never used
again (all of your 1-17 writers will never be used
again). To avoid keeping
them in the sink's internal list of writers, the
idleTimeout is a specified
number of seconds in which no data is received by
the BucketWriter. After
this time, the writer will try to close itself and
will then tell the sink
to remove it, thus freeing up everything used by
the bucketwriter.
So the idleTimeout is just a setting to help limit
memory usage by the hdfs
sink. The ideal time for it is longer than the
maximum time between events
(capped at the rollInterval) - if you know you'll
receive a constant stream
of events you might just set it to a minute or
something. Or if you are fine
with having multiple files open per hour, you can
set it to a lower number;
maybe just over the average time between events.
For me in just testing, I
set it >= rollInterval for the cases when no
events are received in a given
hour (I'd rather keep the object alive for an
extra hour than create files
every 30 minutes or something).
Hope that was helpful,
- Connor
On Thu, Jan 17, 2013 at 12:07 PM, Bhaskar V.
Karambelkar
<[email protected] <mailto:[email protected]>>
wrote:
Say If I have
a1.sinks.k1.hdfs.path = /flume/events/%y-%m-%d/
hdfs.rollInterval=60
Now, if there is a file
/flume/events/2013-01-17/flume_XXXXXXXXX.tmp
This file is not ready to be rolled over yet,
i.e. 60 seconds are not
up and now it's past 12 midnight, i.e. new day
And events start to be written to
/flume/events/2013-01-18/flume_XXXXXXXX.tmp
will the file 2013-01-17 never be rolled over,
unless I have something
like hdfs.idleTimeout=60 ?
If so how do flume sinks keep track of files
they need to rollover
after idealTimeout ?
In short what's the exact use of idealTimeout
parameter ?
