Re: Tomcat DB Connection pool timeBetweenEvictionRunsMillis

[Christopher Schultz]

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Steve,

On 6/4/20 16:59, Sanders, Steve wrote:
> I'm working with an application team that wishes to set the
> timeBetweenEvictionRunsMillis setting of their database connection
> pool to a very low setting - 20ms.
Hah!

Sorry. Continue...

> According to the documentation
> (https://tomcat.apache.org/tomcat-8.5-doc/jdbc-pool.html), this
> setting should never be set below 1000ms, so I'm weary to allow
> this. Their claim is that application performance is poor when set
> to our default of 2000ms. To me this indicates that there is a bug
> in the application itself not closing connections after it is done
> with them and have to wait for an idle connection to be created by
> the pool, causing the performance lag.

My experience suggests that you are right.

> I'm curious if this advice in the documentation is given based on
> performance concerns or if there is some other underlying issue
> that could present itself if this setting is below 1000 ms?

With a 20ms eviction run, you are going to be thrashing the CPU with
that thread. Sure, the CPU can handle many context-switches in a short
amount of time, but evicting lost database connections isn't something
that really should be done /aggressively/ IMO.

- -chris
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Tomcat DB Connection pool timeBetweenEvictionRunsMillis

[Sanders, Steve]

Hi all,

Tomcat Version - 8.5.55
OS - OL7

I'm working with an application team that wishes to set the 
timeBetweenEvictionRunsMillis setting of their database connection pool to a 
very low setting - 20ms. According to the documentation 
(https://tomcat.apache.org/tomcat-8.5-doc/jdbc-pool.html), this setting should 
never be set below 1000ms, so I'm weary to allow this. Their claim is that 
application performance is poor when set to our default of 2000ms. To me this 
indicates that there is a bug in the application itself not closing connections 
after it is done with them and have to wait for an idle connection to be 
created by the pool, causing the performance lag.

I'm curious if this advice in the documentation is given based on performance 
concerns or if there is some other underlying issue that could present itself 
if this setting is below 1000 ms?

Thanks!
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