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From Xiaobin She <xiaobin...@gmail.com>
Subject Re: What's the best practice of loading logs into hdfs while using hive to do log analytic?
Date Tue, 07 Feb 2012 14:09:45 GMT
hi Bejoy and Alex,

thank you for your advice.

Actually I have look at Scribe first, and I have heard of Flume.

I look at flume's user guide just now, and flume seems promising, as Bejoy
said , the flume collector can dump data into hdfs when the collector
buffer reaches a particular size of after a particular time interval, this
is good and I think it can solve the problem of data delivery latency.

But what about compress?

from the user's guide of flume, I see that flum supports compression  of
log files, but if flume did not wait until the collector has collect one
hour of log and then compress it and send it to hdfs, then it will  send
part of the one hour log to hdfs, am I right?

so if I want to use thest data in hive (assume I have an external table in
hive), I have to specify at least two partiton key while creating table,
one for day-month-hour, and one for some other time interval like ten
miniutes, then I add hive partition to the existed external table with
specified partition key.

Is the above process right ?

If this right, then there could be some other problem, like the ten miniute
logs after compress is not big enough to fit the block size of hdfs which
may couse lots of small files ( for some of our log id, this may come
true), or if I set the time interval to be half an hour, then at the end of
hour, it may still cause the data delivery latency problem.

this seems not a very good solution, am I making some mistakes or
misunderstanding here?

thank you very much!

2012/2/7 alo alt <wget.null@googlemail.com>

> Hi,
> a first start with flume:
> http://mapredit.blogspot.com/2011/10/centralized-logfile-management-across.html
> Facebook's scribe could also be work for you.
> - Alex
> --
> Alexander Lorenz
> http://mapredit.blogspot.com
> On Feb 7, 2012, at 11:03 AM, Xiaobin She wrote:
> > Hi all,
> >
> > Sorry if it is not appropriate to send one thread into two maillist.
> > **
> > I'm tring to use hadoop and hive to do some log analytic jobs.
> >
> > Our system generate lots of logs every day, for example, it produce about
> > 370GB logs(including lots of log files) yesterday, and every day the logs
> > increases.
> >
> > And we want to use hadoop and hive to replace our old log analysic
> system.
> >
> > We distinguish our logs with logid, we have an log collector which will
> > collect logs from clients and then generate log files.
> >
> > for every logid, there will be one log file every hour, for some logid,
> > this hourly log file can be 1~2GB
> >
> > I have set up an test cluster with hadoop and hive, and I have run some
> > test which seems good for us.
> >
> > For reference, we will create one table in hive for every logid which
> will
> > be partitoned by hour.
> >
> > Now I have a question, what's the best practice for loading logs files
> into
> > hdfs or hive warehouse dir ?
> >
> > My first thought is,  at the begining of every hour,  compress the log
> file
> > of the last hour of every logid and then use the hive cmd tool to load
> > these compressed log files into hdfs.
> >
> > using  commands like "LOAD DATA LOCAL inpath '$logname' OVERWRITE  INTO
> > TABLE $tablename PARTITION (dt='$h') "
> >
> > I think this can work, and I have run some test on our 3-nodes test
> > clusters.
> >
> > But the problem is, there are lots of logid which means there are lots of
> > log files,  so every hour we will have to load lots of files into hdfs
> > and there is another problem,  we will run hourly analysis job on these
> > hourly collected log files,
> > which inroduces the problem, because there are lots of log files, if we
> > load these log files at the same time at the begining of every hour, I
> > think  there will some network flows and there will be data delivery
> > latency problem.
> >
> > For data delivery latency problem, I mean it will take some time for the
> > log files to be copyed into hdfs,  and this will cause our hourly log
> > analysis job to start later.
> >
> > So I want to figure out if we can write or append logs into an compressed
> > file which is already located in hdfs, and I have posted an thread in the
> > mailist, and from what I have learned, this is not possible.
> >
> >
> > So, what's the best practice of loading logs into hdfs while using hive
> to
> > do log analytic?
> >
> > Or what's the common methods to handle problem I have describe above?
> >
> > Can anyone give me some advices?
> >
> > Thank you very much for your help!

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