[Gluster-devel] Performance Translators' Stability and Usefulness - Regression test outline

[Mickey Mazarick]

Wow, you really hit my biggest fear, the one thing I try to test for... 
data corruption. 
That's what I wake up afraid of at night...

I'm doing a simplified version of the first set of testing you mentioned 
but nothing as detailed. Really creating a random file and doing an md5 
check on it, but now that you mention all the possabilities of files 
moving in from the back end I'm really doing nothing to test the dht or 
namespace distrobution at all....
I would add a few but I haven't had the time to google how to do the 
following without writing a C prog:
check flock()   
check mmap writing
Also I have yet to get this to work all the time but starting a large 
write, and losing a brick under afr.. (usually term the write)

 I'm thinking a simple collection of bash or perl scripts would work for 
a first pass at this. Do you have any suggestions on a good colab site 
for scripting?  If we came up with a basic format we could create and 
then mix and match them as we saw fit. We just need them all to be 
called with the same args, then have a master run that executes all of 
them in a tests dir.  It would also be nice if there was a sort of 
standard output both for giving to devels as well as rolling up nicely 
if we get 1E3 of these things.

-Mic


Geoff Kassel wrote:
> Hi Mickey,
>
>   
>> Thanks I am well versed in unit testing but probably disagree on level
>> of use in a development cycle. Instead of writing a long email back
>> about testing theory, nondeterministic problems, highly connected
>> dependent systems blah blah
>>     
>
> Sorry, I was just trying to make sure we were all on the same page - define 
> some common terminology, etc for anyone else who wanted to join in.
>
> I'm well aware of the limits of testing, having most of a PhD in related 
> formal methods topics and having taught Uni subjects in this area. (But 
> consider me optimistic anyway :)
>
> It's just about improving confidence, after all. Not about achieving some 
> nebulous notion of perfection.
>
>   
>> I'll just say that most of the problems that 
>> have plagued me have been because of interactions between translators,
>> kernel mods etc which unit testing doesn't really approach.
>>     
>
> That's the focus of integration testing, not unit tests... I did mention 
> integration testing.
>
>   
>> Since I'm running my setup as a storage farm it just doesn't matter to
>> me if there's a memory leak of if a server daemon crashes, I have cron
>> jobs that restart it and I barely take notice.
>>     
>
> You're very lucky that a crash doesn't cause you much annoyance. My annoyances 
> in this area are well documented in the list, so I won't repeat them again :)
>
>   
>> I would rather encourage the dev team to add hotadd
>> upgrade and hotadd features. These things would keep my cluster going
>> even if there were catastrophic problems.
>>     
>
> These are good features to have, yes. However, I'd like to make sure there's 
> something incorrupted to recover first.
>
> If a feature freeze was necessary to get a proper QA framework put in place 
> and working towards avoiding more data corruption bugs, then I would vote for 
> the feature freeze over more features, no matter how useful.
>
>   
>> What I'm saying is that a good top down testing system is something we
>> can discuss here, spec out and perhaps create independently of the
>> development team. I think what most people want is a more stable product
>> and I think a top down approach will get it there faster than trying to
>> implement a given UT system from the bottom up. It will defiantly answer
>> the question "should I upgrade to this release?"
>>     
>
> Alright. We'll let the devs concentrate on bottom up testing (they know the 
> code better anyway), and we in the wider community can look at top down 
> testing.
>
>   
>> You mentioned that you had outlines some integration and function tests
>> previously, perhaps you could paste some into this thread so that we
>> could expand on them.
>>     
>
> Okay. The test I outlined was for checking for data corruption bugs for AFR 
> and Unity with cryptographic hashes. The idea actually expands into a class 
> of test cases. I'll flesh those out a bit more now.
>
> Generate a number of files of varying length (zero size, single byte, transfer 
> block size - 1, transfer block size, transfer block size + 1, multiple meg, 
> multiple gig etc) in a directory tree of varying depths. Take the 
> cryptographic hash of each file.
>
> One test can be starting with an empty set of GlusterFS back end data blocks. 
> Insert the files and directories through the client - check the hashes of the 
> files stored on the back ends, and as read back through each of the 
> client(s). If the hashes mismatch the original computed hashes at any point, 
> the test has failed.
>
> Another test can be starting with the files already on the back end. (But 
> without having had Gluster assign metadata attributes yet.) Start the server, 
> read the files through each of the client(s) and directly from the back end. 
> As before, if the hashes mismatch at any point - failure.
>
> A third test - start another set of back ends with a partially populated back 
> end. Start the server, read the existing files off, compare hashes. Add the 
> remaining files. Compare the hashes of all files through the client(s), and 
> as they end up on the back end.
>
> I don't know if 2.0.x Gluster supports this any more, but you used to be able 
> to have one back end populated and the other empty, so long as a namespace 
> block on all servers had zero-length file entries for all of the replicated 
> files. (This being how you could add a node to your cluster originally.) 
> Start back ends in this one populated, others empty configuration - read all 
> the files through from a client connected only to a server with an empty back 
> end. Check the hashes read through the client, and the hashes of the files 
> that end up 'healed' onto the formerly empty back ends.
>
> Then there's a multitude of overwrite tests that could be done in this vein, 
> as well as concurrent read and write tests to check atomicity etc.
>
> All these tests could be done under different performance translators, with 
> different numbers of servers and clients. All just a matter of different 
> configuration files given, and different scripts to set up different test 
> environments.
>
> All of these functional tests can be automated, can be done on a single system 
> with some clever configuration files, or performed across a network to try to 
> detect issues caused by networking.
>
> (I believe there are open source network simulation tools that might be able 
> to be used to simulate lag, noise, congestion etc, and so reduce this network 
> testing to being run on a single machine. Network simulation is not an area 
> of expertise for me, so I don't know how effective or comparable this is to 
> the real thing.)
>
> If the files in the tests are algorithmically generated (say, sourced from a 
> pseudo random number generator, or the various patterns favoured by memory 
> testers), the back end test data sets can be quite small in size.
>
> (Hopefully this will all be small enough to add to the repository without 
> adding much bulk to a check out.)
>
> What do you think?
>
> Geoff.
>
> On Wed, 8 Jul 2009, Mickey Mazarick wrote:
>   
>> Geoff,
>> Thanks I am well versed in unit testing but probably disagree on level
>> of use in a development cycle. Instead of writing a long email back
>> about testing theory, nondeterministic problems, highly connected
>> dependent systems blah blah I'll just say that most of the problems that
>> have plagued me have been because of interactions between translators,
>> kernel mods etc which unit testing doesn't really approach.
>>
>> Since I'm running my setup as a storage farm it just doesn't matter to
>> me if there's a memory leak of if a server daemon crashes, I have cron
>> jobs that restart it and I barely take notice. True a regression testing
>> would get rid of the memory leak you hate but if they have to start from
>> the ground up I would rather encourage the dev team to add hotadd
>> upgrade and hotadd features. These things would keep my cluster going
>> even if there were catastrophic problems.
>>
>> What I'm saying is that a good top down testing system is something we
>> can discuss here, spec out and perhaps create independently of the
>> development team. I think what most people want is a more stable product
>> and I think a top down approach will get it there faster than trying to
>> implement a given UT system from the bottom up. It will defiantly answer
>> the question "should I upgrade to this release?"
>>
>> You mentioned that you had outlines some integration and function tests
>> previously, perhaps you could paste some into this thread so that we
>> could expand on them.
>>
>> Thanks!
>> -Mickey Mazarick
>>
>> Geoff Kassel wrote:
>>     
>>> Hi Mickey,
>>>    Just so that we're all on the same page here - a regression test suite
>>> at its most basic just has to include test cases (i.e. a set of inputs)
>>> that can trigger a previously known fault in the code if that fault is
>>> present. (i.e it can see if the code has 'regressed' into a condition
>>> where a fault is present.)
>>>
>>>    What it's also taken to mean (and typically includes) is a set of
>>> tests cases covering corner cases and normal modes of operation, as
>>> expressed in a set of inputs to code paired with a set of expected
>>> outputs that may or may not include error messages.
>>>
>>>    Test cases aimed at particular levels of the code have specific
>>> terminology associated with those levels. At the lowest level, the method
>>> level, they're called unit tests. At the module/API level - integration
>>> tests. At the system/user interface level - system aka function aka
>>> functional aka functionality tests.
>>>
>>>    When new functionality is introduced or a bug is patched, the
>>> regression test suite (which in the case of unit tests is typically fully
>>> automated) is run to see whether the expected behaviour occurs, and none
>>> of the old faults recur.
>>>
>>>    A lot of the tests you've described fall into the category of function
>>> tests - and from my background in automated testing, I know we need a bit
>>> more than that to get the stability and reliability results we want.
>>> (Simply because you cannot test every corner case within a project the
>>> size and complexity of GlusterFS reliably from the command line.)
>>>
>>>    Basically, what GlusterFS needs is a fairly even coverage of test
>>> cases at all the levels I've just mentioned.
>>>
>>>    What I want to see particularly - and what the devs stated nearly a
>>> year ago was already in existence - is unit tests. Particularly the kind
>>> that can be run automatically.
>>>
>>>    This is so that developers (inside the GlusterFS team or otherwise)
>>> can hack on a piece of code to fix a bug or implement new functionality,
>>> then run the unit tests to see that they (mostly likely) haven't caused a
>>> regression with their new code.
>>>
>>>    (It's somewhat difficult for outsiders to write unit and integration
>>> tests, because typically only the original developers have the in-depth
>>> knowledge of the expected behaviour of the code in the low level detail
>>> required.)
>>>
>>>    Perhaps developed in parallel should be integration and function
>>> tests. Tests like these (I've outlined elsewhere specifically what kind)
>>> would have quite likely picked up the data corruption bugs before they
>>> made their way into the first 2.0.x releases.
>>>
>>>    (Pretty much anyone familiar with the goal of the project can write
>>> function tests, documenting in live code their expectations for how the
>>> system should work.)
>>>
>>>    Long running stability and load tests like you've proposed are also
>>> kinds of function tests, but without the narrowly defined inputs and
>>> outputs of specific test cases. They're basically the equivalent of mine
>>> shaft canaries - they signal the presence of race conditions, memory
>>> leaks, design flaws, and other subtle issues, but often without specifics
>>> as to what 'killed' the canary. Once the cause is found though, a new,
>>> more specific test case can be added at the appropriate level.
>>>
>>>    (Useful, yes, but mostly as a starting point for more intensive QA
>>> efforts.)
>>>
>>>    The POSIX compliance tests you mentioned are more traditional function
>>> level tests - but I think the GlusterFS devs have wandered a little away
>>> from full POSIX compliance on some points, so these tests may not be 100%
>>> relevant.
>>>
>>>    (This is not necessarily a bad thing - the POSIX standard is
>>> apparently ambiguous at times, and there is some wider community feeling
>>> that improvements to the standard are overdue. And I'm not sure the POSIX
>>> standard was ever written with massively scalable, plugable, distributed
>>> file systems in mind, either :)
>>>
>>>    I hope my extremely long winded rant here :) has explained adequately
>>> what I feel GlusterFS needs to have in a regression testing system.
>>>
>>> Geoff.
>>>
>>> On Tue, 7 Jul 2009, Mickey Mazarick wrote:
>>>       
>>>> What kind of requirements does everyone see as necessary for a
>>>> regression test system?
>>>> Ultimately the best testing system would use the tracing translator and
>>>> be able to run tests and generate traces for any problems that occurs,
>>>> giving us something very concrete to provide the developers. That's a
>>>> few steps ahead however, initially we should start to outline some must
>>>> haves in terms of how a test setup is run. obviously we want something
>>>> we can run for many hours or days to test longterm stability, and it
>>>> would be nice if there was some central way to spin up new clients to
>>>> test reliability under a load.
>>>>
>>>> For basic file operation tests I use the below:
>>>> An initial look would be to use some tools like
>>>> http://www.ntfs-3g.org/pjd-fstest.html
>>>> I've seen it mentioned before but it's a good start to test anything
>>>> posix. Here's a simple script that will download and build it if it's
>>>> missing, and run a test on a given mount point.
>>>>
>>>>
>>>> #!/bin/bash
>>>> if [ "$#" -lt 1 ]
>>>> then
>>>>   echo "usage: $0 gluster_mount"
>>>>   exit 65
>>>> fi
>>>> GLUSTER_MOUNT=$1
>>>> INSTALL_DIR="/usr"
>>>> if [ ! -d $INSTALL_DIR/fstest ]; then
>>>>   cd $INSTALL_DIR
>>>>   wget http://www.ntfs-3g.org/sw/qa/pjd-fstest-20080816.tgz
>>>>   tar -xzf pjd-fstest-20080816.tgz
>>>>   mv pjd-fstest-20080816 fstest
>>>>   cd fstest
>>>>   make
>>>>   vi tests/conf
>>>> fi
>>>> cd $GLUSTER_MOUNT
>>>> prove -r $INSTALL_DIR/fstest/
>>>>
>>>> Jacques Mattheij wrote:
>>>>         
>>>>> hello Anand, Geoff & others,
>>>>>
>>>>> This pretty much parallels my interaction with the team about a
>>>>> year ago, lots of really good intentions but no actual follow up.
>>>>>
>>>>> We agreed that an automated test suite was a must and that a
>>>>> whole bunch of other things would have to be done to get
>>>>> glusterfs out of the experimental stage and into production
>>>>> grade.
>>>>>
>>>>> It's a real pity because I still feel that glusterfs is one of the
>>>>> major contenders to become *the* cluster file system.
>>>>>
>>>>> A lot of community goodwill has been lost, I've kept myself
>>>>> subscribed to this mailing list because I hoped that at some
>>>>> point we'd move past this endless cat and mouse game with
>>>>> stability issues but for some reason that never happend.
>>>>>
>>>>> Anand, you have a very capable team of developers, you have
>>>>> a once-in-a-lifetime opportunity to make this happen please
>>>>> take Geoff's comments to hart and get serious about Q&A and
>>>>> community support because that is the key to any successful
>>>>> foss project. Fan that fire and you can't go wrong, lose the
>>>>> community support and your project might as well be dead.
>>>>>
>>>>> I realize this may come across as harsh but it is intended to
>>>>> make it painfully obvious that the most staunch supporters
>>>>> of glusterfs are getting discouraged and that is a loss no
>>>>> serious project can afford.
>>>>>
>>>>>  Jacques
>>>>>
>>>>> Geoff Kassel wrote:
>>>>>           
>>>>>> Hi Anand,
>>>>>>    If you look back through the list archives, no one other than me
>>>>>> replied to the original QA thread where I first posted my patches.
>>>>>> Nor to the Savannah patch tracker thread where I also posted my
>>>>>> patches. (Interesting how those trackers have been disabled now...)
>>>>>>
>>>>>>    It took me pressing the issue after discovering yet another bug
>>>>>> that we even started talking about my patches. So yes, my patches
>>>>>> were effectively ignored.
>>>>>>
>>>>>>    At the time, you did mention that the code the patches were to be
>>>>>> applied against was being reworked, in addition to your comments
>>>>>> about my code comments.
>>>>>>
>>>>>>    I explained the comments as being necessary to avoid the automated
>>>>>> tool flagging potential issues again on reuse of that tool - other
>>>>>> comments for future QA work. There was no follow up on that from you,
>>>>>> nor suggestion on how I might improve these comments to your
>>>>>> standards.
>>>>>>
>>>>>>    I continued to supply patches in the Savannah tracker against the
>>>>>> latest stable 1.3 branch - which included some refactoring for your
>>>>>> reworked code, IIRC - for some time after that discussion. All of my
>>>>>> patches were in sync with the code from publically available 1.3
>>>>>> branch repository within days of a new TLA patchset.
>>>>>>
>>>>>>    None of these were adopted either.
>>>>>>
>>>>>>    I simply ran out of spare time to maintain this patchset, and I
>>>>>> got tired of pressing an issue (QA) that you and the dev team clearly
>>>>>> weren't interested in.
>>>>>>
>>>>>>    I don't have the kind of spare time needed to do the sort of
>>>>>> in-depth re-audit your code from scratch (as would be needed) in the
>>>>>> manner that I did back then. So I can't meet your request at this
>>>>>> time, sorry.
>>>>>>
>>>>>>    As I've suggested elsewhere, now that you apparently have the
>>>>>> resources for a stand-alone QA team - this team might want to at
>>>>>> least use the tools I've used to generate these patches - RATS and
>>>>>> FlawFinder.
>>>>>>
>>>>>>    That way you can generate the kind of QA work I was producing with
>>>>>> the kind of comment style you prefer.
>>>>>>
>>>>>>    The only way I can conceive of being able to help now is in
>>>>>> patching individual issues. However, I can really only feasibly do
>>>>>> that with my time constraints if I've got regression tests to make
>>>>>> sure I'm not inadvertently breaking other functionality.
>>>>>>
>>>>>>    Hence my continued requests for these.
>>>>>>
>>>>>> Geoff.
>>>>>>
>>>>>> On Tue, 7 Jul 2009, Anand Avati wrote:
>>>>>>             
>>>>>>>>   I've also gone one better than just advice - I've given up
>>>>>>>> significant
>>>>>>>> portions of my limited spare time to audit and patch a
>>>>>>>> not-insignificant
>>>>>>>> portion of the GlusterFS code, in order to deal with the stability
>>>>>>>> issues
>>>>>>>> I and others were encountering. My patches were ignored, on the
>>>>>>>> grounds
>>>>>>>> that it contained otherwise unobtrusive comments which were quite
>>>>>>>> necessary to the audit.
>>>>>>>>                 
>>>>>>> Geoff, we really appreciate your efforts, both on the fronts of your
>>>>>>> patch submissions and for voicing your opinions freely. We also
>>>>>>> acknowledge the positive intentions behind this thread. As far as
>>>>>>> your patch submissions are concerned, there is probably a
>>>>>>> misunderstanding. Your patches were not ignored. We do value your
>>>>>>> efforts. The patches which you submitted, even at the time of your
>>>>>>> submission were not applicable to the codebase.
>>>>>>>
>>>>>>> Patch 1 (in glusterfsd.c) -- this file was reworked and almost
>>>>>>> rewritten from scratch to work as both client and server.
>>>>>>>
>>>>>>> Patch 2 (glusterfs-fuse/src/glusterfs.c) -- this module was
>>>>>>> reimplemented as a new translator (since a separate client was no
>>>>>>> more needed).
>>>>>>>
>>>>>>> Patch 3 (protocol.c) -- with the introduction of non blocking IO and
>>>>>>> binary protocol, nothing of this file remained.
>>>>>>>
>>>>>>> What I am hoping to convey is that, the reason your patches did not
>>>>>>> make it to the repository was because it needed significant reworking
>>>>>>> to even apply. I did indeed comment about code comments of the style
>>>>>>> /* FlawFinder: */ but then, that definitely was _not_ the reason they
>>>>>>> weren't included. Please understand that nothing was ignored
>>>>>>> intentionally.
>>>>>>>
>>>>>>> This being said, I can totally understand the efforts which you have
>>>>>>> been putting to maintain patchsets by yourself and keeping them up to
>>>>>>> date with the repository. I request you to resubmit them (with git
>>>>>>> format-patch) against the HEAD of the repository.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Avati
>>>>>>>               
>>>>>> _______________________________________________
>>>>>> Gluster-devel mailing list
>>>>>> Gluster-devel at nongnu.org
>>>>>> http://lists.nongnu.org/mailman/listinfo/gluster-devel
>>>>>>             
>
>
>   


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