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Re: How to run Fault injection in HDFS
Thanks for looking into fault injection - it's very interesting and useful
technique based on AspectJ.

Currently, it is fully integrated into HDFS only. There's a JIRA (HADOOP-6204)
which tracks the same effort for Common and then all Hadoop's components will
have injection (as well as fault injection) in place. This JIRA should be
committed in the matter of a couple of weeks.

For the immediate purpose you don't need to patch anything or do any tweaking of
the code: the fault injection framework is in already and ready to work.

For your current needs: to be able to run HDFS with instrumented code you need
to run a special build. To do so:
  - % ant injectfaults - similar to a 'normal' build, but does instrument the
code with aspects located under src/test/aop/**
  - % ant jar-fault-inject - similar to a 'normal' jar creation but instrumented
  - % ant jar-test-fault-inject - similar to a 'normal' jar-test creation but
instrumented

Now, if you have the rest of sub-projects built you need to move the
instrumented jar files on top of the 'normal' files in your installation
directory. Please note that some renaming has to be done: injected jar files
have '-fi' suffix in their names and normal jar files don't have such. Thus
currently you'll have to rename those injected jars to pretend like they are
normal, used by configured's classpath.

At this point you all set: you have a production quality Hadoop with injected
HDFS. As soon as the aforementioned JIRA is ready and committed we'd be able to
provide Hadoop-injected version by the build's means rather than doing any
renaming and manual intervention.

Also, if you need to read more about fault injection (FI) in HDFS you can find
FI-framework documentation in the current HDFS trunk (it isn't on the web yet
for version 0.21 hasn't been released yet). Because building documentation
requires some extra effort and additional software to be installed, you can
simply download and read the PDF from this FI-framework JIRA

https://issues.apache.org/jira/secure/attachment/12414225/Fault+injection+development+guide+and+Framework+HowTo.pdf

Hope it helps,
   Cos

On 10/8/09 8:10 AM, Thanh Do wrote:
> Thank you so much, Jakob.
>
> Could you please explain the fault injection running procedure in details?
>
> My goal is running HDFS in a cluster (with a namenode and several
> datanode), and see how fault injection techniques affect HDFS
> behavior's. Also, I would like to define some new aspects/fault to test
> the system.
>
> What I did was:
> 1) I checked out the hadoop-common-trunk, but this package doesn't
> contain HDFS classes. I finally noticed that FI framework is currently
> integrated with HDFS only.
>
> 2) So, I checked out the hdfs-trunk. The build.xml contain injectfaults
> target and several other related things. I was able to build those
> targets (injectfaults, run-test-hdfs-fault-inject, etc). Up to this
> point, I stucked because I found no scripted that help me to start-dfs,
> stop-dfs...
> I copied the bin folder from common/core to HDFS project folder and ran
> the  script:
>
> /bin/start-dfs.sh/
>
> but there is exception:
>
> /Exception in thread
> main"Java.lang.NoClassDefFoundError
> : org/apache/commons/logging/LogFactory
> /
> I guess the reason is I ran HDFS without any common class. How I get
> around this?
>
> 3) I also tried the third way, by download the hadoop release (contain
> everything: core, hdfs, mapred), and used Eclipse to create project from
> existing code. I was able to build this project. The bin scripts worked
> well but I found know FI related classes. What I did was apply the patch
> (HADOOP-6003.patch) using Eclipse patch command (Team | apply patch),
> but I failed the patching procedure.
>
> In summary, I would like to run a real HDFS with fault injection. I am
> not very familiar with ant. Could you please show me some more details,
> so that I could get around this?
>
> On Thu, Oct 8, 2009 at 12:19 AM, Jakob Homan <[EMAIL PROTECTED]

With best regards,
Konstantin Boudnik (aka Cos)

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