Ok I should state that I haven't used OCM, but from looking at it I
think it binds to javax.jcr.*
if not, ignore my comments (but please let me know so I learn :) )
On 28 Apr 2009, at 15:44, majohnst wrote:
Thanks for the response. To give a little more information about my
situation, we are not seeing excess sql traffic, we are more
concerned with
the time required to execute a query from the repository.
In our setup, we are using a Spring/Tomcat setup and using
Jackrabbit OCM to
map our entities. We have noticed that as the number of concurrent
users on
our website increases, the query performance goes way down. So our
page load
times increase dramatically. As best as I can tell, the pages are
waiting
for a jackrabbit query to execute and a backlog of jackrabbit
operations
begins to form, slowing down the page loads. When you say jackrabbit
is
multi-threaded:
Ian Boston wrote:
Jackrabbit has its own multi threaded state management. Everything is
focused on serving information from memory and not performing a query
against the database. Only when a session needs to get something that
isn't in one of the shared caches will you see queries hitting the
database.
Do you mean that it is executing queries against the repository in a
multi-threaded way (many concurrent queries)?
I think we need to differentiate queries.
Queries above jackrabbit at the javax.jcr level are either direct
(javax.jcr.Session.getNode() etc), indirect Node.getNode() or
javax.jcr.query.*. All of these go through the jcr Session which is
not thread safe but there will be 1000's and they will be able to
access shared node state *without* generating SQL Queries.
So there can and will be many javax.jcr.* 'queries' all multi threaded.
AFAIK, java.sql.Connections are not generally thread safe (driver
dependent) so SQL queries will be serialized even if multiple threads
are requesting them.
Since we are using spring in a
web app, is this considered one session, or multiple sessions?
If spring uses a single java.jcr.Session then it will be one. I would
expect it to use one per request thread.
The ultimate
goal is to increase the speed of our queries. We have already read
over the
tips regarding how to write queries effectively and how to structure
the
repository. Now I am thinking we are running into code issues either
with
the Jackrabbit query logic or in OCM mapping that is slowing the
process
down.
I think you need an OCM expert (not me sorry) as it could be that
there is something going on there.
If you want to check that Jackrabbit itself is the problem, rather
than OCM, try using apache benchmark against a JCR repository.
eg
ab -c200 -n1000
http://localhost:8080/some/url/that/gets/the/content/of/a/jcr/file.html
ie 200 concurrent threads, each thread requesting 1000 times.
Ian
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