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From Ahmed Vila <av...@devlogic.eu>
Subject Re: Need suggestion on reliable source for log processing
Date Thu, 13 Nov 2014 17:56:30 GMT
Hi Saravana,

I think there is no override for the .completed suffix.
Also, I think there is no way for Flume to distinguish which file it
already processed and which not.

On Thu, Nov 13, 2014 at 4:54 AM, SaravanaKumar TR <saran0081986@gmail.com>
wrote:

> Hi Ahmed,
>
> I have a  query with flume spool directory option.
>
> Is that possible to ignore fileSuffix option in spool dir source.It seems
> by default it will append .COMPLETED suffix.I don't want to append any
> suffix to the ingested file.
>
> Please let me  know if its possible.
>
> Thanks,
> Saravana
>
> On Mon, Oct 27, 2014 at 7:25 PM, Ahmed Vila <avila@devlogic.eu> wrote:
>
>> You're welcome.
>>
>> Well... there will be at least "failed due to burned down hardware" :)
>>
>> Joke aside, there will be no solution with 100% certainty for a long time
>> to come.
>> As I see it, that is simply because maturity difference between software,
>> so you have to use some mumbo-jumbo techniques in order to make them to
>> work together without modifications.
>> I consider tail-f a mumbo-jumbo technique, but Flume community has been
>> nice enough to support level that low.
>>
>> If you care, you can implement full object-level logging in your
>> application via Avro and utilize Flume up to his potential... as well as
>> handling back-offs as you find appropriate.
>> But for such purpose there is also Flume's implementation of the log4j
>> appender, so you basically send all logs directly to the flume.
>> Not sure how back-offs are handled, but that's the level at which
>> applications should communicate.
>>
>> On the other hand, directory spool is mature to it's finest details,
>> supported by any application, altered easily... so that's why I have used
>> it.
>>
>>
>> On Mon, Oct 27, 2014 at 2:39 PM, SaravanaKumar TR <saran0081986@gmail.com
>> > wrote:
>>
>>> Ahmed,
>>>
>>> Thanks for your details comments.
>>>
>>> Final point, in which cases these logging solution will be considered as
>>> a perfect system without  any tradeoffs,
>>>
>>> On Mon, Oct 27, 2014 at 6:47 PM, Ahmed Vila <avila@devlogic.eu> wrote:
>>>
>>>> Exactly up to the point.
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, Oct 27, 2014 at 1:57 PM, SaravanaKumar TR <
>>>> saran0081986@gmail.com> wrote:
>>>>
>>>>> That was a good point.
>>>>>
>>>>> So if a solution mention as guarantee data delivery , it specifies
>>>>> that  only in the case when the event flows into the source/producers
>>>>> successfully by application and then from that point the system guarantee
>>>>> the event delivery till other end sink/consumer.
>>>>>
>>>>> It has no control over the proper flow of event reaching the
>>>>> source/producer.(like data loss)
>>>>>
>>>>> So there always be chances of data loss when the system goes down ,
>>>>> where certain tradeoff measures to be taken.
>>>>>
>>>>> On Mon, Oct 27, 2014 at 6:06 PM, Ahmed Vila <avila@devlogic.eu>
wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Flume, Kafka, or any other system can only be responsible for it's
>>>>>> own actions. Looking from the perspective of the exec source in Flume
- it
>>>>>> requests from the bash to give him an output from his stout. It cannot
>>>>>> control what bash will return.
>>>>>> Thus, it's not a file to him, but just a stream of text.
>>>>>>
>>>>>> When spooling directory source is in question, it will resume from
>>>>>> the file it failed with.
>>>>>> That reveals two approaches to event consumption: push and pull.
>>>>>>
>>>>>> When push approach is used then it cannot be aware of what comes
next
>>>>>> and what was before it started to listen.
>>>>>>
>>>>>> Even so, some sources/producers, even they use pull approach, doesn't
>>>>>> have to know how to return to the last read event. It's up to
>>>>>> implementation.
>>>>>>
>>>>>> Regards,
>>>>>> Ahmed
>>>>>>
>>>>>>
>>>>>> On Mon, Oct 27, 2014 at 12:48 PM, SaravanaKumar TR <
>>>>>> saran0081986@gmail.com> wrote:
>>>>>>
>>>>>>> yes , I agree .
>>>>>>>
>>>>>>> I think no logging solution like source in flume/producer in
kafka
>>>>>>>  have  any marking feature like exact point till it consumed
from logfile ,
>>>>>>> to recover  incase of its failure to again start reading from
the same
>>>>>>> point of the logfile.(before failure)
>>>>>>>
>>>>>>> This is the major point where failures were difficult to ignore.Am
I
>>>>>>> right?
>>>>>>>
>>>>>>> On Mon, Oct 27, 2014 at 4:51 PM, Ahmed Vila <avila@devlogic.eu>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> You can use spillable channel that will store events in memory
and
>>>>>>>> once it fills it, it will spill to the disk.
>>>>>>>> Also, you can use file channel, but it's as fast as your
disk is
>>>>>>>> and it's suggested to use a separate disk for it due to high
IO with it,
>>>>>>>> preferably an SSD.
>>>>>>>>
>>>>>>>> But, that will not solve the issue you might run into - if
the
>>>>>>>> flume fails for whatever the reason, you'll never be able
to continue from
>>>>>>>> the exact point where it failed.
>>>>>>>> Yes, File channel preserves the state, so it will continue
with
>>>>>>>> whatever he already received, but what about the time while
it was down ?
>>>>>>>>
>>>>>>>> If you cannot change anything regarding the application that
>>>>>>>> produces the logs, then such circumstance has to be taken
as a trade off.
>>>>>>>>
>>>>>>>>
>>>>>>>> On Mon, Oct 27, 2014 at 12:09 PM, SaravanaKumar TR <
>>>>>>>> saran0081986@gmail.com> wrote:
>>>>>>>>
>>>>>>>>> Yes I understand the concerns with this use case.
>>>>>>>>>
>>>>>>>>> If so we need to configure failover in this scenario
, can we have
>>>>>>>>> it like channel level ,sink channel.
>>>>>>>>>
>>>>>>>>> Does flume support to configure failover incase channel
fills up.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Mon, Oct 27, 2014 at 3:54 PM, Ahmed Vila <avila@devlogic.eu>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>> In fact, this is not the problem with Flume.
>>>>>>>>>>
>>>>>>>>>> No solution will function reliably for your use case,
simply
>>>>>>>>>> because all of them will have to do some sort of
tail-f or streaming on a
>>>>>>>>>> file and if they can't keep up with it (they mostly
don't in high speed
>>>>>>>>>> entry points), they will drop some entries.
>>>>>>>>>> Please, be kind to yourself and plan for failures
- if you need
>>>>>>>>>> to restart Flume or any other solution then you'll
face dropped entries
>>>>>>>>>> that you'll not be able to re-ingest easily as in
most cases you won't know
>>>>>>>>>> which ones you've dropped.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Regards,
>>>>>>>>>> Ahmed
>>>>>>>>>>
>>>>>>>>>> On Mon, Oct 27, 2014 at 11:13 AM, SaravanaKumar TR
<
>>>>>>>>>> saran0081986@gmail.com> wrote:
>>>>>>>>>>
>>>>>>>>>>> Thanks for comments Ahmed.
>>>>>>>>>>>
>>>>>>>>>>> So from your comments , I consider that flume
doesn't have any
>>>>>>>>>>> reliable source option for use case provided
by me.
>>>>>>>>>>>
>>>>>>>>>>> If flume can't provide it, can you help me with
any other log
>>>>>>>>>>> collector solutions which can I consider here
to move real time data to
>>>>>>>>>>> HDFS.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Mon, Oct 27, 2014 at 3:37 PM, Ahmed Vila <avila@devlogic.eu>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Hi,
>>>>>>>>>>>>
>>>>>>>>>>>> Then, you're out of luck in my opinion, as
there is no way
>>>>>>>>>>>> other than tail -f.
>>>>>>>>>>>> The problem with fail-f is that tail will
not wait for
>>>>>>>>>>>> source/channel to keep up with it. If Cnannel
is full it will back-off to
>>>>>>>>>>>> the source and then the source will just
stop ingesting.
>>>>>>>>>>>>
>>>>>>>>>>>> There is a possibility to hack up the tail
-f into another file
>>>>>>>>>>>> and then custom-rotate that duplicate file.
>>>>>>>>>>>> But, I wouldn't recommend such case.
>>>>>>>>>>>>
>>>>>>>>>>>> Just a side note - If you're operating Java
application (Tomcat
>>>>>>>>>>>> or similar), then you can create multiple
output files via log4j.properties
>>>>>>>>>>>> configuration without application itself
knowing anything about it.
>>>>>>>>>>>>
>>>>>>>>>>>> Regards,
>>>>>>>>>>>> Ahmed
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On Mon, Oct 27, 2014 at 10:56 AM, SaravanaKumar
TR <
>>>>>>>>>>>> saran0081986@gmail.com> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> Ahmed,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Here in my case , the application will
rename the existing
>>>>>>>>>>>>> file as <logfile>.yesterdaydate
and create a new file as <logfile> at 00:00
>>>>>>>>>>>>> AM.
>>>>>>>>>>>>>
>>>>>>>>>>>>> I can't change the log rotation policy
of application for
>>>>>>>>>>>>> now.So I guess I should rule out the
option of using spooling directory
>>>>>>>>>>>>> source in my case.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Can you suggest me with any other options
other than spooling
>>>>>>>>>>>>> dir source.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Mon, Oct 27, 2014 at 3:10 PM, Ahmed
Vila <avila@devlogic.eu
>>>>>>>>>>>>> > wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> It all depends on how log rotation
is done and how
>>>>>>>>>>>>>> application producing the log file
handles log rotation.
>>>>>>>>>>>>>> Most of the applications just reopens
the log file when it
>>>>>>>>>>>>>> receives a kill signal. For example,
nginx reopens the log file when it
>>>>>>>>>>>>>> receives USR1 signal, but it doesn't
stop the process. Some applications
>>>>>>>>>>>>>> might restart as a result.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> If the application just reopens the
log file, then you can
>>>>>>>>>>>>>> change your log rotation policy to
be per minute.
>>>>>>>>>>>>>> In that case logrotate daemon won't
satisfy such case, so
>>>>>>>>>>>>>> you'll have to make a cron job to
do it.
>>>>>>>>>>>>>> In such case, you would separate
finished logs location and
>>>>>>>>>>>>>> live log location so the spooling
directory source doesn't freak out about
>>>>>>>>>>>>>> active log file being appended.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Anyway, spooling directory source
is a way to go, as it will
>>>>>>>>>>>>>> leave log files in place, just renamed.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Regards,
>>>>>>>>>>>>>> Ahmed
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Mon, Oct 27, 2014 at 10:21 AM,
SaravanaKumar TR <
>>>>>>>>>>>>>> saran0081986@gmail.com> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I am using Apache flume 1.5.0.Quick
setup explanation here.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Source:exec , tail –F command
for a logfile.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Channel:  file channel
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Sink: HDFS
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Use case:to move real time data
from logfile to HDFS.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> It appears like exec is not a
reliable source , as we may
>>>>>>>>>>>>>>> data loss if channel/source is
down.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> So i tried with other option
"spooling directory source"
>>>>>>>>>>>>>>> which is mentioned as reliable
source.But here I have a single logfile
>>>>>>>>>>>>>>> where data gets appended in ,
so I dont see option of moving the file to
>>>>>>>>>>>>>>> spool directory.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Can anyone help me with providing
any other reliable source
>>>>>>>>>>>>>>> option in case where logfile
gets appended with data and logfile rotation
>>>>>>>>>>>>>>> happens only at the end of the
day.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Saravana
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
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>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> ------------------------------------------------------------
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>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>>
>>>>>>>> Best regards,
>>>>>>>> Ahmed Vila | Senior software developer
>>>>>>>> DevLogic | Sarajevo | Bosnia and Herzegovina
>>>>>>>>
>>>>>>>> Office : +387 33 942 123
>>>>>>>> Mobile: +387 62 139 348
>>>>>>>>
>>>>>>>> Website: www.devlogic.eu
>>>>>>>> E-mail   : avila@devlogic.eu
>>>>>>>> ------------------------------------------------------------
>>>>>>>> ---------
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>>>>>>>> ------------------------------------------------------------
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>>>>>>>>
>>>>>>>
>>>>>>
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>>>>>
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>>>
>>>
>>
>>
>> --
>>
>> Best regards,
>> Ahmed Vila | Senior software developer
>> DevLogic | Sarajevo | Bosnia and Herzegovina
>>
>> Office : +387 33 942 123
>> Mobile: +387 62 139 348
>>
>> Website: www.devlogic.eu
>> E-mail   : avila@devlogic.eu
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>
>


-- 

Best regards,
Ahmed Vila | Senior software developer
DevLogic | Sarajevo | Bosnia and Herzegovina

Office : +387 33 942 123
Mobile: +387 62 139 348

Website: www.devlogic.eu
E-mail   : avila@devlogic.eu
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