Inconsistent output of 'mogadm domain list' encountered

[Chaos Wang]

Emm...I'm afraid making modifications only in
MogileFS::Domain::reload_domains() won't be enough...

The MogileFS::Domain::delete() method called
MogileFS::Domain::invalidate_cache() instead of reload_domains(), so if
you deleted a domain, then try to retrieve domain instance through
MogileFS::Domain::of_dmid() with the deleted domain's ID, the issue will
come up again.

I have no idea about the reason of having cache invalidation code both
in reload_domains() and invalidate_cache(), but it seems to be a better
solution to keep that code only in invalidate_cache() and have
reload_domains() calling it at first.

This issue don't need parallel environment to be revealed, here is the
corresponding testing snippet I appended in
mogilefs/server/t/domains-classes.t :

MogileFS::Domain->create("bar");
my $tmp_dom=MogileFS::Domain->of_namespace("bar");
my $tmp_dmid=$tmp_dom->{dmid};
$tmp_dom->delete;
ok(!defined(MogileFS::Domain->of_dmid($tmp_dmid)), "no domain info
remained in cache after deletion");

dormando wrote:
> Fixed both instances in trunk...
>
> They were trivial changes (although I put the cache clear in a different
> place), but I might not have totally understood the original goals of
> the singleton caches. Feel free to berate my fail :)
>
> Also haven't figured a decent test, since the issue tends to happen in
> parallel processes. Any ideas?
>
> -Dormando
>
> Frank Ng wrote:
>   
>> We see the same thing in our test mogilefs env.  i made a change of
>> mindevcount from 2 to 3 and ran mogadm class list a few times, it's show
>> alternating results.
>>  
>> [root at xxx mogdata]# mogadm class list
>>   domain               class                mindevcount
>> -------------------- -------------------- -------------
>>  snf_test01           default                   2
>>  snf_test01           snf_hr                    2
>>  snf_test01           snf_lr                    3 <--
>>  
>> [root at xxx mogdata]# mogadm class list
>>  domain               class                mindevcount
>> -------------------- -------------------- -------------
>>  snf_test01           default                   2
>>  snf_test01           snf_hr                    2
>>  snf_test01           snf_lr                    2 <--
>>  
>> [root at xxx mogdata]# mogadm domain list
>>  domain               class                mindevcount
>> -------------------- -------------------- -------------
>>  snf_test01           default                   2
>>  snf_test01           snf_hr                    2
>>  snf_test01           snf_lr                    2 <--
>>  
>> [root at xxx mogdata]# mogadm domain list
>>  domain               class                mindevcount
>> -------------------- -------------------- -------------
>>  snf_test01           default                   2
>>  snf_test01           snf_hr                    2
>>  snf_test01           snf_lr                    3 <--
>>
>>  
>> On Wed, Mar 12, 2008 at 3:58 AM, Chaos Wang <chaoslawful at gmail.com
>> <mailto:chaoslawful at gmail.com>> wrote:
>>
>>     Hi,
>>
>>     I use the MogileFS code from official svn trunk to do some test. But
>>     when I do some domain addition/deletion operations, the output of
>>     'mogadm domain list' becomes inconsistent between different calls.
>>     This phenomenon can be repeated by following steps:
>>
>>        1. mogadm domain add xxx
>>        2. mogadm domain delete xxx
>>        3. mogadm domain add yyy
>>        4. mogadm domain list (several times)
>>
>>     I thinks the problem is in the invalidate_cache() method in
>>     MogileFS::Domain module, because it forget to clean up the hash map
>>     %singleton (of_dmid(), which is called in domains(), used this hash
>>     map before trying %id2name map). After made the following changes in
>>     MogileFS::Domain::invalidate_cache(), the phenomenon doesn't show up
>>     again:
>>
>>     --code begin--
>>     sub invalidate_cache {
>>     ...
>>     %id2name=();
>>     %name2id=();
>>     %singleton=(); # XXX: this is newly added
>>     ...
>>     --code end--
>>
>>     And I have another question: does classes belong to certain domain?
>>     If so, why delete a domain does not clean up the classes under it?
>>
>>
>>     
>
>
>