Re: [hibernate-dev] Hibernate Search: configure the LockingFactory
The issue is closed already:
http://fisheye.labs.jboss.com/browse/Hibernate/search/trunk
I'll add support to create LockFactories by fqcn later, I didn't
consider that important
at first.
answers inline:
2009/2/18 Emmanuel Bernard <emmanuel(a)hibernate.org>:
On Feb 16, 2009, at 15:06, Sanne Grinovero wrote:
> Hi all,
> to solve HSEARCH-284 (Lucene locks left around in application
> restart/crash)
> I am investigating the differences in all Lucene's LockFactory
> implementations;
> some of them are interesting and I would like to add a configuration
> option to
> replace the default one in Hibernate Search.
>
> 1) property name:
> I'm naming the property key "locking_strategy", scoped for each
> DirectoryProvider.
sounds good
>
>
> 2) values:
> At first I was planning to use the usual design to be able to specify
> any implementation
> by specifying the qualified class name, but actually only 4
> implementations make sense
> and if someone really needed the flexibility to implement their own
> they can define
> their own DirectoryProvider and use whatever they want.
hum, does that makes our codebase more complex to support custom
LockFactories? I would like this flexibility/
>
> Also 2 of the base Lucene implementations are missing a public no-args
> constructor,
> so I would use only simple names:
>
> simple -> org.apache.lucene.store.SimpleFSLockFactory
> native -> org.apache.lucene.store.NativeFSLockFactory
> single -> org.apache.lucene.store.SingleInstanceLockFactory
> none -> org.apache.lucene.store.NoLockFactory
yes, simple names for those that make sense and fqcn for the others. We
might also support a "factory" so that impl wo no-arg constructor can be
used, but that's an enhancement we can do later if needed.
I avoided support for "fqcn" and factories to keep it simple;
I'll add support for both for consistency and because you seem to like them.
>
>
> 3) support for "none":
> I don't think we should let the user select something which is not
> compatible
> with H.Searche's design, so I am still trying to figure out if the
> NoLockFactory
> could be an option in case Search is the only process accessing the index.
> Currently inside search the IndexReaders/Searchers are read-only, and at
> most
> one IndexWriter is using the DP, so the locking strategy could be set
> to "none" IMHO.
> opinions?
that sounds reasonable but how does that differ from
SingleInstanceLockFactory?
the single instance locking has a java in memory lock, so to protect
yourself in case of using several indexwriter/readers on the same index
making changes when all running in the same JVM.
The "none" doesn't protect at all, so you have to make sure to never open
a second indexwriter or use any indexwriter when you are using an indexreader
to make changes.
Sounds a bit dangerous IMHO but I don't think we should stop people shooting
at their own feet.
As we are enforcing a single indexwriter and all our indexreaders are
readonly since
last release, you may want to use it: I think the current design of H.Search
doesn't stop us from offering this option.
I've added a note in the docs to use it only if you really understand it.
>
>
> 4) default:
> The current default is "simple", which has the problem as reported in
> HSEARCH-284,
> so I was puzzled by the idea to define the "native" as the default one to
> have
> Search beginners avoid the locking problem, but I am hitting some
> problems under load testing,
> so I think the default should stay to "simple" at least for now.
OK