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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: DBCP params different for the Tomcat JDBC (not DBCP) implementation in Tomcat 8?
Date Wed, 07 Oct 2015 19:50:49 GMT
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Bradley,

On 10/7/15 3:21 PM, Bradley Wagner wrote:
> Ah, I see what you're saying. My apologies for not seeing that
> sooner.
> 
> That post was also very helpful in explaining why both exist.
> Thank you!

It's definitely confusing to those you don't already understand.
"DBCP" usually just means "database connection pool", but in the
Apache world, it usually specifically means commons-dbcp.

> Is it your recommendation then to use DBCP 2 over Tomcat JDBC in
> Tomcat 8? If so, I think it would be helpful to have a page on the
> public Tomcat website about why both exist and which one is
> recommended.

The general recommendation is to use the default pool (commons-dbcp).

Unless you have narrowed a performance problem to the pool itself,
there's no reason to use one over the other. I suspect that there are
only a few companies in the world where the connection pool
implementation's overhead makes a noticeable difference in the
performance of their web applications.

Not doing a million transactions a minute? Don't worry about a thing.

> Also, in my case, after some more digging, I found that Tomcat JDBC
> was simply ignoring my badly named params. I had specified
> maxWaitMillis="5000" in my <Resource> in context.xml. Yet on
> initialization, I saw the following in my log:
> 
> Using DataSource 
> [org.apache.tomcat.jdbc.pool.DataSource@41a91006{ConnectionPool[defaul
tAutoCommit=null;
>
> 
defaultReadOnly=null; defaultTransactionIsolation=-1; defaultCatalog=nul
l;
> driverClassName=com.mysql.jdbc.Driver; maxActive=100; maxIdle=10; 
> minIdle=10; initialSize=10; maxWait=30000; testOnBorrow=true; 
> testOnReturn=false; timeBetweenEvictionRunsMillis=5000; 
> numTestsPerEvictionRun=0; minEvictableIdleTimeMillis=60000; 
> testWhileIdle=false; testOnConnect=false; password=********; 
> url=jdbc:mysql://localhost:3306/<REDACTED>?useUnicode=true&characterEn
coding=UTF-8;
>
> 
username=root; validationQuery=SELECT 1; validationQueryTimeout=-1;
> validatorClassName=null; validationInterval=30000; 
> accessToUnderlyingConnectionAllowed=true; removeAbandoned=false; 
> removeAbandonedTimeout=300; logAbandoned=true;
> connectionProperties=null; initSQL=null; jdbcInterceptors=null;
> jmxEnabled=true;
> 
> which shows maxWait=30000.

Of course. No component is going to guess that the number you put in
configuration (5000) should be applied to some other setting.

> So it looks Tomcat JDBC is forgiving with badly named params in
> that it doesn't fail on startup. Whereas if I try to instantiate a
> Tomcat JDBC DataSource directly, it fails when I try to set
> properties that don't exist.

I think this has more to do with the tolerance of the Spring
configuration component relative to the tolerance of the Tomcat
configuration component: both are creating a new DataSource and
calling setFoo() on them, but only Spring fails when a setter is not
available, while Tomcat just gives a warning and continues on its way.

- -chris
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