Re: [c3p0-users] "Checking for expired resources" every second
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Re: [c3p0-users] "Checking for expired resources" every second
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From: Steve W. <swa...@mc...> - 2007-02-24 02:30:11
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Luke,
The default propertyCycle is not fixed at 1 second. One second is the
maximum possible frequency actually. The default
effectivePropertyCycle is based on the various timings you've set
c3p0 to enforce, including maxConnectionAge, maxIdleTime,
maxIdleTimeExcessConnections, and idleConnectionTestPeriod. If any of
these are set to a very tight value, then the effectivePropertyCycle
will be short.
Under the present implementation, if an explicit propertyCycle is not
set, expiration and scheduled-test checks will occur every <minimum-
timimng-param>/4 seconds but no more frequently than once a second.
The idea is that implementation of user-set timings should not be off
by more than 25%. Ordinarily this is fine -- if expired resource or
testing-due checks are performed frequently, it is because users have
configured frequent tests. But, as you've seen, you can set this
interval however you'd like. (But, if you set an maxIdleTime of 5
seconds and a propertyCycle of 10 seconds, it's possible that a
Connection will remain idle for up to 15 seconds before being culled.
Under the default effectivePropertyCycle, the longest an idle
Connection could survive would be 6.25 seconds.)
Note that frequent expiration or test-required checks don't slow
things down much. These are quick, in-memory checks of internal
datastructures. Connections are not actually tested or expired except
at user-specified intervals.
Note also that you can check the effectivePropertyCycle parameter
(programmatically or via JMX) of any c3p0 PooledDataSource. This will
either be the propertyCycle you've explicitly set, or c3p0's default
if you haven't set one.
good luck!
Steve
On Feb 23, 2007, at 2:40 PM, Luke Dang wrote:
> Ok, I've found it: propertyCycle
>
> When not set, a "suitable" period will be set automatically, which
> is 1
> sec. Isn't that a bit too frequent?
>
> Thanks.
> Luke
>
> Luke Dang wrote:
>> Hi,
>> I'm quite new to c3p0. I've noticed that the pool checks for expired
>> resources every second, as shown below. Is there a way to change this
>> interval?
>> Thanks.
>> Luke
>>
>> [Timer-4] DEBUG com.mchange.v2.resourcepool.BasicResourcePool -
>> Checking for expired resources - Fri Feb 23 10:54:41 EST 2007
>> [com.mchange.v2.resourcepool.BasicResourcePool@fab5b1]
>> [Timer-4] DEBUG com.mchange.v2.resourcepool.BasicResourcePool -
>> BEGIN
>> check for expired resources.
>> [com.mchange.v2.resourcepool.BasicResourcePool@fab5b1]
>> [Timer-4] DEBUG com.mchange.v2.resourcepool.BasicResourcePool -
>> FINISHED check for expired resources.
>> [com.mchange.v2.resourcepool.BasicResourcePool@fab5b1]
>> [Timer-4] DEBUG com.mchange.v2.resourcepool.BasicResourcePool -
>> Checking for expired resources - Fri Feb 23 10:54:42 EST 2007
>> [com.mchange.v2.resourcepool.BasicResourcePool@fab5b1]
>> [Timer-4] DEBUG com.mchange.v2.resourcepool.BasicResourcePool -
>> BEGIN
>> check for expired resources.
>> [com.mchange.v2.resourcepool.BasicResourcePool@fab5b1]
>> [Timer-4] DEBUG com.mchange.v2.resourcepool.BasicResourcePool -
>> FINISHED check for expired resources.
>> [com.mchange.v2.resourcepool.BasicResourcePool@fab5b1]
>>
>>
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