Hi,
I'm trying to use DBCP 1.2.1 and 1.2.2 (as supplied with Tomcat 6.0.14
resp 6.0.16). I've set the pool's configuration to be a fixed size. My
(test) config is this:
<Resource
name="jdbc/test_ds"
factory="org.apache.tomcat.dbcp.dbcp.BasicDataSourceFactory"
type="javax.sql.DataSource"
scope="Shareable"
auth="Container"
driverClassName="org.postgresql.Driver"
username="*****" password="******"
url="*****"
poolPreparedStatements="true"
accessToUnderlyingConnectionAllowed="false"
defaultAutoCommit="true"
defaultReadOnly="false"
defaultTransactionIsolation="READ_COMMITTED"
validationQuery="select 1"
testOnBorrow="true"
testOnReturn="false"
testWhileIdle="false"
initialSize="5"
minIdle="5"
maxIdle="5"
maxActive="5"
maxWait="10"
removeAbandoned="true"
removeAbandonedTimeout="10"
logAbandoned="true"
timeBetweenEvictionRunsMillis="2000"
minEvictableIdleTimeMillis="10000"
numTestsPerEvictionRun="5"
/>
This seems to be a fixed size pool to me. However, in my postgresql log
I see that every ~10 seconds all 5 connections are closed and
immediately opened again:
2008-10-31 13:26:09 CET LOG: connection received: host=localhost port=38231
2008-10-31 13:26:09 CET LOG: connection received: host=localhost port=38232
2008-10-31 13:26:09 CET LOG: connection received: host=localhost port=38233
2008-10-31 13:26:09 CET LOG: connection received: host=localhost port=38234
2008-10-31 13:26:09 CET LOG: connection received: host=localhost port=38235
2008-10-31 13:26:09 CET LOG: connection received: host=localhost port=38236
2008-10-31 13:26:20 CET LOG: disconnection: session time: 0:00:10.690
user=test database=test_db host=localhost port=38232
2008-10-31 13:26:20 CET LOG: disconnection: session time: 0:00:10.686
user=test database=test_db host=localhost port=38233
2008-10-31 13:26:20 CET LOG: disconnection: session time: 0:00:10.668
user=test database=test_db host=localhost port=38236
2008-10-31 13:26:20 CET LOG: disconnection: session time: 0:00:10.675
user=test database=test_db host=localhost port=38235
2008-10-31 13:26:20 CET LOG: connection received: host=localhost port=38237
2008-10-31 13:26:20 CET LOG: disconnection: session time: 0:00:10.683
user=test database=test_db host=localhost port=38234
2008-10-31 13:26:20 CET LOG: connection received: host=localhost port=38238
2008-10-31 13:26:20 CET LOG: connection received: host=localhost port=38239
2008-10-31 13:26:20 CET LOG: connection received: host=localhost port=38240
2008-10-31 13:26:20 CET LOG: connection received: host=localhost port=38241
2008-10-31 13:26:31 CET LOG: disconnection: session time: 0:00:10.999
user=test database=test_db host=localhost port=38237
2008-10-31 13:26:31 CET LOG: disconnection: session time: 0:00:10.993
user=test database=test_db host=localhost port=38238
2008-10-31 13:26:31 CET LOG: disconnection: session time: 0:00:10.990
user=test database=test_db host=localhost port=38239
2008-10-31 13:26:31 CET LOG: disconnection: session time: 0:00:10.988
user=test database=test_db host=localhost port=38240
2008-10-31 13:26:31 CET LOG: disconnection: session time: 0:00:10.985
user=test database=test_db host=localhost port=38241
Of course, these timings are consistent with the time set for
"minEvictableIdleTimeMillis". Nevertheless, I don't really understand
why the pool closes all 5 and then immediately re-opens them. Since
minIdle is set to 5, even though connections have been idle for more
than 10 seconds, there seems to be no point in closing them. In general,
there seems to be no point in closing idle connections such that the
total number of them falls below minIdle.
Maybe I'm missing something though. Basically I only want to have an
evictor thread running for checking abandoned connections. Since I have
a fixed size pool, I don't care about any idle connections being closed.
Maybe related to this, on the documentation page
(http://commons.apache.org/dbcp/configuration.html), the term "idle"
seems to be used for both the condition that a connection sits in the
pool, waiting for being requested, and the condition that client code
has requested a connection and failed to return it to the pool within
some time frame. This slightly adds to the confusion I have with
understanding these settings.
Kind regards,
Arjan Tijms
--
It's a cult. If you've coded for any length of time, you've run across someone
from this warped brotherhood. Their creed: if you can write complicated code,
you must be good.
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