10 Aug
2016
10 Aug
'16
4:33 p.m.
On Wed, Aug 10, 2016 at 12:41 PM, Fabian Pichler
<fabian.pichler(a)synventis.com> wrote:
ok, if I understand correctly the API contract so far
is, that the context
defines the database used and the reference of the document to load
must only be taken relative to the given context. (old String fullName
and context-database interpretation).
Yes.
So, I think it would be better to compute the lookup key based on the
context database and the fullName computed out of the document reference.
Otherwise you would not get the same document in both situations.
1. from cache
2. freshly loaded
Yes this what I explained.
Anyway, I am not sure if it is a good idea to fix the key-issue as part of
XWIKI-13623. I think that XWIKI-13623 should only focus on the mentioned
memory visability and resulting data loss issue.
I did not told you to do it as part of XWIKI-13623 but you cannot do
XWIKI-13623 without cleaning a bit the way cache key is handled right
now in the method since from what I understood you depend on a proper
cache key (to access the right DocumentLoader) in the solution you
proposed.
Fabian.
2016-08-10 10:52 GMT+02:00 Thomas Mortagne <thomas.mortagne(a)xwiki.com>om>:
--
Thomas Mortagne
On Wed, Aug 10, 2016 at 10:14 AM, Fabian Pichler
<fabian.pichler(a)synventis.com> wrote:
--
Thomas Mortagne
_______________________________________________
devs mailing list
devs(a)xwiki.org
http://lists.xwiki.org/mailman/listinfo/devs
_______________________________________________
devs mailing list
devs(a)xwiki.org
http://lists.xwiki.org/mailman/listinfo/devs Hi Thomas
Thanks for responding and thanks for supporting the suggested solution.
I understand the doc.Key-issue that you mentioned. Yet, I think this is
not
a
XWikiCacheStore#loadXWikDoc concern. In my understanding the expected
document
to load is defined by the document-reference and the language. Thus the
Hibernate-Store must be concerned in setting the context database
according
to the Wiki-Reference before loading the
document. This is acctually
already
done in the XWiki#getDocument call. I agree that
this might be the wrong
place to do it.
Thus, I would suggest to fix this issue in the XWikiHibernateStore on a
seperate jira-issue.
In an ideal world it would be fixed in XWikiHibernateStore I agree but
this would break retro compatibility (yeah always a pain). That's why
I talked about providing a new API.
So right now in practice using a combination of context wiki and
document reference is part of the API definition and can be applied at
XWikiCacheStore too.
Note that in practice this is actually a pretty rare case since anyone
is supposed to use XWiki#getDocument which make sure the context
contain the document wiki. But this can still happen since this is a
very old and public API.
Maybe this could be combined with a significant
performance improvment in
loading
the documents with fewer sql-queries per loading action.
With XWIKI-13623 I try to tackle the issue about randomly loosing
BaseObject
data because of an not thread safe construction
and publication of
XWikiDocument
java objects in XWikiCacheStore. Because this issue gave us a big
headache
in
production multiple times, I solved it in our project in the way
mentioned.
If the xwiki-dev team supports the suggested solution, I would be willing
to proceed
and prepare a pull request for an adapted XWikiCacheStore fix.
Kind regards,
Fabian
2016-08-08 12:07 GMT+02:00 Thomas Mortagne <thomas.mortagne(a)xwiki.com>om>:
> XWikiCacheStore#loadXWikiDoc is actually a bit tricker than that right
> now for retro compatibility and laziness (really need to rewrite this
> whole store API) reasons and before applying what you propose the way
> it deals with document uid should be modified a bit.
>
> Hibernate store is always loading the document from the wiki indicated
> in the context completely ignoring the wiki in the XWikiDocument
> object. That means that doc.getKey() may be different than the key of
> the document that will actually come from the hibernate store. So
> before adding DocumentLoader jingling a first thing to do is generate
> the initial cache key with a mix of the wiki id located in the context
> and the XWikiDocument reference.
>
> Then what you propose sounds good.
>
> On Mon, Aug 8, 2016 at 8:53 AM, Fabian Pichler
> <fabian.pichler(a)synventis.com> wrote:
> > Hi devs
> >
> > http://jira.xwiki.org/browse/XWIKI-13623
> > I would like to discuss the suggested solution, before I start
> implementing
> > it:
> >
> > *I suggest the following solution:*
> > Introducing a nested DocumentLoader class which loads the document
> calling
> > the basestore loadXWikiDoc in a synchronized getDocOrLoad method. The
> > DocumentLoader objects gets instantiated in the cacheStore on a cache
> miss.
> > It then gets stored in a ConcurrentHashMap using the same key which is
> used
> > for the document cache (DocumentReference including language). Using
> > putIfAbsent to insert the DocumentLoader and calling the synchronized
> load
> > method on the object in the map solves the memory visibility issue and
> > moreover ensures that the same XWikiDocument is not loaded multiple
times
> > concurrently from the database. It is
still possible to load different
> > documents in parallel. A DocumentLoader will load the XWikiDocument
only
> > once and the returns the identical
document object on any following
call
of
> the synchronized getDocOrLoad method.
>
> WDYT?
>
> Kind Regards,
> Fabian
> _______________________________________________
> devs mailing list
> devs(a)xwiki.org
> http://lists.xwiki.org/mailman/listinfo/devs
--
Thomas Mortagne
_______________________________________________
devs mailing list
devs(a)xwiki.org
http://lists.xwiki.org/mailman/listinfo/devs
_______________________________________________
devs mailing list
devs(a)xwiki.org
http://lists.xwiki.org/mailman/listinfo/devs