You're right about the max # of concurrent users, but the max # of required connections is usually < the max # of concurrent users. Cayenne only needs a connection to query the db or to commit to the db. Outside of those operations, connections are returned to the pool, so you can usually get by with significantly fewer connections. I think you're on the right track with gradually increasing the max connections as opposed to gradually decreasing them.
Cheers, Robert On Dec 11, 2011, at 12/1111:57 PM , Chris Murphy (www.strandz.org) wrote: > I just had a look at the Modeler and at the DomainNode's JDBC Configuration > (in the Main tab). I saw that 'Max Connections' was set to '1'. So perhaps > I wasn't giving Cayenne much to play with in terms of connection pooling! I > have now set it to '2'. (I imagine the default was a bit higher than these > numbers). > > In the program at the moment there ought to be at most two DataContexts. > And one connection each is enough. So two should suffice until I go for the > recommended approach with multiple users of having a DataContext per user. > In that case I imagine 'Max Connections' will be related to the expected > maximum number of concurrent users. But multi-user configuration is for > another day... > > So far this server program hasn't fallen over... And I don't think there's > any reason why I would need more than 2 connections is there? I like to > keep everything as tight as possible - 3 connections would actually be an > error that I would like to know about. > > Thank you ~ Chris Murphy > > On 12 December 2011 16:15, Robert Zeigler <robert.zeig...@roxanemy.com>wrote: > >> Hm. Cayenne is usually pretty good about managing the connection pooling >> for you. >> How many concurrent connections is your mysql db configured to allow? >> >> Robert >> >> On Dec 11, 2011, at 12/119:58 PM , Chris Murphy (www.strandz.org) wrote: >> >>> Thanks Robert, >>> >>> That was the answer. The memory leak disappeared. I now create a >>> DataContext with 'method scope' that gets gc-ed when the method has >>> finished. That brought up what must be another problem with my code which >>> I'm investigating now: >>> >>> Caused by: org.apache.cayenne.CayenneRuntimeException: [v.3.0 Apr 26 2010 >>> 09:59:17] Error detecting database type: Data source rejected >> establishment >>> of connection message from server: "Too many connections" >>> at >> org.apache.cayenne.dba.AutoAdapter.loadAdapter(AutoAdapter.java:185) >>> at org.apache.cayenne.dba.AutoAdapter.getAdapter(AutoAdapter.java:155) >>> at >>> org.apache.cayenne.dba.AutoAdapter.getExtendedTypes(AutoAdapter.java:263) >>> at >> org.apache.cayenne.access.DataNode.performQueries(DataNode.java:243) >>> at >>> >> org.apache.cayenne.access.DataDomainQueryAction.runQuery(DataDomainQueryAction.java:422) >>> at >>> >> org.apache.cayenne.access.DataDomainQueryAction.access$000(DataDomainQueryAction.java:69) >>> at >>> >> org.apache.cayenne.access.DataDomainQueryAction$2.transform(DataDomainQueryAction.java:395) >>> at >>> >> org.apache.cayenne.access.DataDomain.runInTransaction(DataDomain.java:850) >>> at >>> >> org.apache.cayenne.access.DataDomainQueryAction.runQueryInTransaction(DataDomainQueryAction.java:392) >>> at >>> >> org.apache.cayenne.access.DataDomainQueryAction.execute(DataDomainQueryAction.java:121) >>> at org.apache.cayenne.access.DataDomain.onQuery(DataDomain.java:743) >>> at >>> >> org.apache.cayenne.util.ObjectContextQueryAction.runQuery(ObjectContextQueryAction.java:333) >>> at >>> >> org.apache.cayenne.util.ObjectContextQueryAction.execute(ObjectContextQueryAction.java:96) >>> at >> org.apache.cayenne.access.DataContext.onQuery(DataContext.java:1278) >>> at >>> org.apache.cayenne.access.DataContext.performQuery(DataContext.java:1267) >>> at >>> >> com.seasoft.store.orm.CayenneInterpretedQuery.execute(CayenneInterpretedQuery.java:265) >>> at com.seasoft.store.DomainQuery.execute(DomainQuery.java:43) >>> at >>> >> com.seasoft.store.DomainQueries.executeRetCollection(DomainQueries.java:56) >>> at >>> >> com.cmts.business.orm.DOActivity.storeRealtimeReadings(DOActivity.java:113) >>> at >>> >> com.cmts.business.SenderGasReceiver.storeRealtimeSamplesIntoSummaryReadings(SenderGasReceiver.java:266) >>> at com.cmts.business.StoreRealtimeIntoDBJob.execut >>> e(StoreRealtimeIntoDBJob.java:20) >>> at org.quartz.core.JobRunShell.run(JobRunShell.java:216) >>> >>> Maybe I need to recycle connections or something?? In the Cayenne >>> documentation I found this: "Cayenne will also periodically close unused >>> database connections if it determines there are too many that are open >> and >>> idle." Is there some way to hint to Cayenne that you've finished with a >>> DataContext's connection pool, something like 'dataContext.close()'? >>> >>> Here is the exception at a lower level: >>> >>> Caused by: java.sql.SQLException: Data source rejected establishment of >>> connection message from server: "Too many connections" >>> at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:1997) >>> at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:1906) >>> at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:2520) >>> at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:817) >>> at com.mysql.jdbc.Connection.createNewIO(Connection.java:1782) >>> at com.mysql.jdbc.Connection.<init>(Connection.java:450) >>> at >>> >> com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:411) >>> at >>> >> org.apache.cayenne.conn.DriverDataSource.getConnection(DriverDataSource.java:156) >>> at >>> >> org.apache.cayenne.conn.PooledConnectionImpl.reconnect(PooledConnectionImpl.java:83) >>> at >>> >> org.apache.cayenne.conn.PooledConnectionImpl.getConnection(PooledConnectionImpl.java:120) >>> at >>> >> org.apache.cayenne.conn.PoolManager.uncheckConnection(PoolManager.java:369) >>> at >>> org.apache.cayenne.conn.PoolManager.getConnection(PoolManager.java:353) >>> at >>> org.apache.cayenne.conn.PoolManager.getConnection(PoolManager.java:330) >>> at >>> >> org.apache.cayenne.access.DataNode$TransactionDataSource.getConnection(DataNode.java:364) >>> at >>> >> org.apache.cayenne.conf.NodeDataSource.getConnection(NodeDataSource.java:46) >>> at >> org.apache.cayenne.dba.AutoAdapter.loadAdapter(AutoAdapter.java:170) >>> >>> Thanks ~ Chris Murphy >>> >>> On 11 December 2011 17:57, Robert Zeigler <robert.zeig...@roxanemy.com >>> wrote: >>> >>>> Note that DataContext creation is cheap. What I typically do in >> situations >>>> like this is to periodically create a new data context that you can >> throw >>>> away. When it's gone, the associated objects will be gc'ed. Eg: you >> could >>>> periodically dump the "reading" data context and create a fresh one >> after >>>> every 1,000 Reading objects or whatever makes sense for your use-case. >> If >>>> the frequency of readings transactions is low, it probably makes sense >> to >>>> create a new DataContext, import whatever objects you need into it (via >>>> localObject), create your readings, commit, then discard the >> DataContext. >>>> If the readings are very frequent, then it makes sense to have a >> dedicated >>>> "readings" DataContext that you can periodically swap out. >>>> >>>> HTH, >>>> >>>> Robert >>>> >>>> On Dec 11, 2011, at 12/1112:51 AM , Chris Murphy (www.strandz.org) >> wrote: >>>> >>>>> I have a server application that continually reads data from sensors. >> At >>>>> set intervals the data is summarized. This summary data is used to >> create >>>>> Cayenne data objects of type Reading. A short transaction commits these >>>>> Reading objects to the database, after which it is not important that >>>> they >>>>> are held in memory - they were created only to be stored. After a long >>>>> period of time their continual collection results in an 'OutOfMemory' >> JVM >>>>> condition. >>>>> >>>>> There are many objects of type Reading for another Cayenne data object >>>>> called SubstancePoint. And there's a whole object graph going back from >>>>> there. I basically want to keep the whole of the object graph in >> memory, >>>>> except for these Reading objects. >>>>> >>>>> Is there a way to 'disappear' data objects from the DataContext? For >> that >>>>> is what I think would solve my problem. I have tried calling >>>>> DataContext.unregisterObjects() post-commit on the Reading data >> objects I >>>>> want evacuated from memory, but I can see that the leak is still going >>>> on. >>>>> >>>>> Thank you ~ Chris Murphy >>>> >>>> >> >>
