Hi Nitish, I'm not sure there is a best answer. In this case it's a bit of a tradeoff. If you're not actively driving work on a connection why would one want to hold on to a connection? Say you have long lived EntityManagers which use resource local transactions. If we maintain the connection until the EntityManager is closed then the connection pool size is 1:1 with the number of EMs (which might be 1 per thread). Right now we're taking the stance that the connection pool is better able to load balance if we return the connection to the pool immediately.
With JTA the scenario changes a bit. In my experience with JTA aware connection pools the connection doesn't really go back to the pool when we (the app) close it. Rather it's reserved for future use in the same JTA tran (this might be implementation specific though). In which case the cleanup which causes a lot of the overhead wouldn't even happen until the JTA tran completes. I'm less familiar with Spring transactions (suppose I have some reading to do). I'm not ready to say either approach is right or wrong. It really depends on your use case. By default we try to keep the number of connections low and avoid contention for database resources which makes sense for bigger applications. Smaller ones might prefer setting retainMode=transaction or always. What this is pointing out to me is that there's some benefit in having an integrated connection pool in a JPA provider. I believe someone posted about the idea a few weeks ago but I don't remember what came of it - based on this thread I think it's worth revisiting. -mike > Hi Michael, > The connection retain mode property makes the numbers almost same, > but I am a little confused. Shouldnt this be the default behavior of Entity > Manager? Typically I would have the entity manager tied up to the > transaction (JTA or Spring), so I would expect Entity Manager to hold the > connection always. > > Thanks and Regards, > Nitish Kumar > > -----Original Message----- > From: Michael Dick [mailto:michael.d.d...@gmail.com] > Sent: Sat 3/21/2009 1:55 AM > To: users@openjpa.apache.org > Subject: Re: Slow performance with OpenJPA when selecting from a ManyToMany > relation. > > Hi all, > > As Paul pointed out privately I didn't indicate which versions of OpenJPA I > was using. I've been testing with 1.2.0, 1.2.1 and 2.0.0-SNAPSHOT > primarily. > I also ran with 1.3.0-SNAPSHOT, and 1.0.3 for comparison - there wasn't > much > difference though so reduced the scope to 1.2 and trunk. > > The testcase uses a single EntityManager instance to issue a batch of > findBy > operations. In OpenJPA each findBy (or any query for that matter) obtains a > connection from the connection pool and returns it after getting the > results. So we're spending a lot of time moving the connection to and from > the pool (some cleanup is done along the way). > > Fortunately this behavior can be configured with the > openjpa.ConnectionRetainMode property. Setting it to "always" causes the > EntityManager to hold on to a single connection until the EntityManager > closes. Obviously this setting introduces the possibility of exhausting the > connection pool if num_entitymanagers > max_connections, but for this > benchmark it's safe to try. > > Setting ConnectionRetainMode gave OpenJPA equivalent times on my laptop at > 100 - 100,000 iterations. In addition I removed the > openjpa.jdbc.SynchronizeMappings property from the example (it's extraneous > once the tables are created anyway).Another option I enabled that made some > difference was preparedStatementCaching in dbcp. I'm assuming EclipseLink > has some pstmt caching as well, but that could be faulty - in which case > I'll disable it in dbcp. > > Here's the entire set of properties I'm using : > properties.put("openjpa.Log", "DefaultLevel=FATAL"); > properties.put("openjpa.RuntimeUnenhancedClasses", "unsupported"); > properties.put("openjpa.ConnectionRetainMode", "always"); > properties.put("openjpa.ConnectionDriverName", > "org.apache.commons.dbcp.BasicDataSource"); > > properties.put("openjpa.ConnectionProperties", String.format( > "DriverClassName=%s, Url=%s, username=%s, password=%s," > + " MaxActive=%s, MaxIdle=%s, MinIdle=%s, MaxWait=%s" > + ", poolPreparedStatements=true" > , JDBC_DRIVER, JDBC_URL, JDBC_USER, > JDBC_PASSWORD, MAX_CON, MIN_CON, MIN_CON, "1000")); > > EntityManagerFactory factory = > Persistence.createEntityManagerFactory("OpenJPAPU", properties); > > MIN_CON = 1, MAX_CON=10. > > Shubbis, could you try running something similar and see if you get the > same > results? > > -mike > > On Fri, Mar 20, 2009 at 8:46 AM, Michael Dick <michael.d.d...@gmail.com > >wrote: > > > Hi, I took a quick run with the source code from the RAR Shubbis attached > > earlier (thanks BTW). > > > > The SQL we execute for this findBy is SELECT t0.warehouseName FROM > > Warehouse t0 WHERE t0.warehouseNr = ?. Pretty basic, and I doubt > EclipseLink > > is doing better (certainly not 3x) based solely on the SQL. > > > > So I started digging deeper and on my laptop (not to be confused with any > > sort of "real" benchmark) there's a sweet spot around 100 iterations. > Under > > 100 OpenJPA is faster. Between 100 and 125 they're comparable, and over > 125 > > iterations EclipseLink starts pulling ahead. > > > > Environment : > > * Entities were enhanced by the PCEnhancer tool prior to running the > tests. > > > > * Connection pooling is enabled for EclipseLink and OpenJPA with roughly > > the same settings. EclipseLink's pool and commons-dbcp weren't an easy > 1:1 > > match, so I might have some investigation to do there. > > * MySQL Connector for Java v 5.1.7. > > * MySQL database running locally, Version: 5.0.67-0ubuntu6 > > * Tests executed in Eclipse, YMMV outside of Eclipse. > > * Sun JDK 5 java full version "1.5.0_15-b04" > > > > I have done a lot of hacking about with the sample application but I > don't > > think I've violated the intent of the exercise. I'll upload the app to a > > jira shortly. > > > > The relevant code is in my pastebin at these links : > > persistence.xml : http://miked.pastebin.com/m490814b7 > > test01.java : http://miked.pastebin.com/m7d3df62f > > WarehouseDAO.java : http://miked.pastebin.com/m49ab9a0e > > > > I highlighted the changed lines in WarehouseDAO, but missed it on the > > others (too many lines to highlight accurately. > > > > I'm still looking, but thought this was worth sharing in case someone > else > > sees something I've missed. > > > > -mike > > > > > > > > On Thu, Mar 19, 2009 at 10:53 AM, Paul Copeland <t...@jotobjects.com > >wrote: > > > >> > >> At one point in this thread it was mentioned that the benchmark ran much > >> faster on a home computer than on an office computer and the reason for > the > >> difference was not obvious. Was that difference explained yet? > >> > >> What version of OpenJPA is the test using? > >> > >> - Paul > >> > >> > >> On 3/19/2009 7:44 AM, Kevin Sutter wrote: > >> > >>> Shubbis and Nitish, > >>> Thanks for your efforts. So, to clarify -- all implementations are > using > >>> similar configurations (ie. connection pooling, caching, enhancement, > >>> etc)? > >>> But, the OpenJPA performance is still 3 times slower than the > >>> competitors? > >>> In all of the scenarios? Or, just with this ManyToMany scenario? I > >>> would > >>> expect some overhead as compared to iBatis and/or straight JDBC, but > >>> OpenJPA > >>> should be competitive (and beat) the Hibernates and EclipseLinks... > Very > >>> frustrating. When we do our comparisons with the industry benchmarks > >>> (Trade > >>> and SpecJApp), OpenJPA is extremely competitive. > >>> > >>> I have not closely examined your benchmark project, so I don't know how > >>> it > >>> compares to Trade and/or SpecJApp work loads. Any thoughts on this > >>> topic? > >>> > >>> One other thought... Just to prove that the enhancement processing is > >>> being > >>> done and you're not falling into the sub-classing support, could you > run > >>> with the following property? This will cause your application to > >>> error-off > >>> if your Entities are not byte-code enhanced. We will not fall into the > >>> sub-classing support which greatly affects the performance. > >>> > >>> <property name="openjpa.RuntimeUnenhancedClasses" > >>> value="warn"/> > >>> > >>> It really seems that you are trying to do a fair comparison, and I > >>> greatly > >>> appreciate your efforts. The last time one of these comparisons was > >>> posted, > >>> the benchmark code and process was flawed. So, I am pleased to see the > >>> efforts associated with this exercise. > >>> > >>> Our performance lead is out having a baby, so we haven't been able to > dig > >>> into your benchmark to the extent that we would like. If we can verify > >>> that > >>> the enhancement processing is happening, that would be good input. > >>> Thanks > >>> for your patience. What kind of timeframe are you under for posting > this > >>> benchmark? > >>> > >>> Thanks, > >>> Kevin > >>> > >>> On Thu, Mar 19, 2009 at 9:05 AM, Shubbis <marius.jo...@broadpark.no> > >>> wrote: > >>> > >>> > >>> > >>>> Since we decided to go with vanilla installations of alle the > frameworks > >>>> we > >>>> have not added the connection pool feature to OpenJPA, until now. > >>>> > >>>> The results are sadly not that great. Yes, it's faster and it doesn't > >>>> run > >>>> out of connections like before, BUT it's still 3, yes, -three- times > >>>> slower > >>>> than Hibernate, EclipseLink, iBatis and regular JDBC when persisting > >>>> entities with many relations. > >>>> > >>>> Clearly this is not the kind of results I was hoping for and I'm quite > >>>> perplexed as to what to do. > >>>> > >>>> Shubbis > >>>> > >>>> > >>>> Nitish Kumar wrote: > >>>> > >>>> > >>>>> Hi subbis, > >>>>> If I let the iteration loop over 5000, I get that exception, It > >>>>> seems (I am not sure) openjpa is creating a new connection and after > a > >>>>> while mysql runs out of connection. I tried the same code and > iteration > >>>>> loop with a connection pool and it works fine. That should get you > >>>>> moving as of now, till someone from Open JPA team looks into the > issue. > >>>>> > >>>>> Thanks and Regards, > >>>>> Nitish Kumar > >>>>> > >>>>> > >>>>> > >>>> -- > >>>> View this message in context: > >>>> > >>>> > http://n2.nabble.com/Slow-performance-with-OpenJPA-when-selecting-from-a-ManyToMany-relation.-tp2466994p2503084.html > >>>> Sent from the OpenJPA Users mailing list archive at Nabble.com. > >>>> > >>>> > >>>> > >>>> > >>> > >>> > >>> > >> > >> > > > > > > ------------------------------------------------------------------------------------------------------------------------- > "The information contained in this e-mail transmission is confidential and > may be privileged. It is intended only for the > addressee(s) stated above. If you are not an addressee, any use, > dissemination, distribution, publication, or copying of > the information contained in this e-mail is strictly prohibited. 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