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https://issues.apache.org/jira/browse/RAVE-838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13489313#comment-13489313
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Chris Geer edited comment on RAVE-838 at 11/2/12 9:30 AM:
----------------------------------------------------------
Using JProfiler, I was able to profile the JPA calls directly for the first
time which is helping shed some light on what's going on. Currently, on 0.17,
when loading the default canonical home page, WdigetRepository.get is called 5
times, UserRepository.get is called 5 times, PersonRepository.get is called 3
times and four other JPA queries are run. Compare that with 0.16 where you just
have the four JPA queries, no direct calls to any repository.get method.
After digging into it a little more I came to the conclusion that it's not the
number of calls that is the sole problem, it's the sheer amount of data loaded
on each call. For example, on each widget call there has to be queries to load
Widgets, WidgetComments, WidgetRatings, WidgetTags and Categories (missed that
split). The frustrating thing is that none of those extra sets of data is
actually used in any of the calls to load the page (that I saw), so we are
loading lots of data (5 times) that is never used on that page. Now, for a lot
of them, there isn't data by default but there is still an attempt to load
data. There is the same problem when you look at person and user. As it turns
out, JPA has a solution to handle scenarios like this, Lazy fetch, which will
only load the sub-data on demand which would be great. When I changed the
Widget object to lazy fetch all the sub data the time spent in those calls
dropped by ~70%. The major problem this introduced however was that the lazy
data was never loaded. I couldn't find a way to fix that but maybe someone else
with more JPA experience could have a look or explain why that's a really bad
idea.
EDIT: Looking at the H2 performance, it looks like each request to H2 spawns a
new thread (or multiple threads). On the load of the canonical home page H2
spanwed (and killed) 16 separate threads on 0.16 and well over 100 separate
threads on 0.17. I can't confirm if those are from a pool or what but that is a
lot of short lived threads.
was (Author: geerzo):
Using JProfiler, I was able to profile the JPA calls directly for the first
time which is helping shed some light on what's going on. Currently, on 0.17,
when loading the default canonical home page, WdigetRepository.get is called 5
times, UserRepository.get is called 5 times, PersonRepository.get is called 3
times and four other JPA queries are run. Compare that with 0.16 where you just
have the four JPA queries, no direct calls to any repository.get method.
After digging into it a little more I came to the conclusion that it's not the
number of calls that is the sole problem, it's the sheer amount of data loaded
on each call. For example, on each widget call there has to be queries to load
Widgets, WidgetComments, WidgetRatings, WidgetTags and Categories (missed that
split). The frustrating thing is that none of those extra sets of data is
actually used in any of the calls to load the page (that I saw), so we are
loading lots of data (5 times) that is never used on that page. Now, for a lot
of them, there isn't data by default but there is still an attempt to load
data. There is the same problem when you look at person and user. As it turns
out, JPA has a solution to handle scenarios like this, Lazy fetch, which will
only load the sub-data on demand which would be great. When I changed the
Widget object to lazy fetch all the sub data the time spent in those calls
dropped by ~70%. The major problem this introduced however was that the lazy
data was never loaded. I couldn't find a way to fix that but maybe someone else
with more JPA experience could have a look or explain why that's a really bad
idea.
> Performance problems after model-split merge
> --------------------------------------------
>
> Key: RAVE-838
> URL: https://issues.apache.org/jira/browse/RAVE-838
> Project: Rave
> Issue Type: Bug
> Affects Versions: 0.17
> Reporter: Chris Geer
> Assignee: Chris Geer
> Fix For: 0.18
>
>
> - WidgetServer/Repository.get is being called much more frequently with the
> RegionWidget/Widget split.
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