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Posted to users@tomcat.apache.org by Rob Sargent <rs...@xmission.com> on 2020/11/20 17:25:24 UTC

Details of connection pooling

I'm using tomcat 9.0.+ and wish to use the built in connection pooling 
to connect to a postgres server.

I would like to understand the lookup mechanism for the next available 
connection. I create a context

    contextResource.setName("jdbc/sgsdb");
    contextResource.setType("javax.sql.DataSource");
    String turl =String.format("jdbc:postgresql://%s:%d/%s", host, port, dbname);
    contextResource.setProperty("url",turl);
    contextResource.setProperty("driverClassName","org.postgresql.Driver");

which names a specific database.  Then I make a user specific connection

    DataSource ds = (DataSource)env.lookup("jdbc/sgsdb");
    conn =ds.getConnection(user, pwd);

1. To access a different database do I need to make a database-specific 
DataSource?

2. Is the username used to locate an available connection for that user 
(maybe creating one if not found) or is the user overlain on an existing 
connection (perhaps "set role user")?

Re: Details of connection pooling

Posted by Phil Steitz <ph...@gmail.com>.

On 11/20/20 10:25 AM, Rob Sargent wrote:
> I'm using tomcat 9.0.+ and wish to use the built in connection pooling 
> to connect to a postgres server.
>
> I would like to understand the lookup mechanism for the next available 
> connection. I create a context
>
>    contextResource.setName("jdbc/sgsdb");
>    contextResource.setType("javax.sql.DataSource");
>    String turl =String.format("jdbc:postgresql://%s:%d/%s", host, 
> port, dbname);
>    contextResource.setProperty("url",turl);
> contextResource.setProperty("driverClassName","org.postgresql.Driver");
>
> which names a specific database.  Then I make a user specific connection
>
>    DataSource ds = (DataSource)env.lookup("jdbc/sgsdb");
>    conn =ds.getConnection(user, pwd);
>
> 1. To access a different database do I need to make a 
> database-specific DataSource?

Yes.

>
> 2. Is the username used to locate an available connection for that 
> user (maybe creating one if not found) or is the user overlain on an 
> existing connection (perhaps "set role user")?

No, all connections from a (default, DBCP BasicDatacsource) pool share 
the same database credentials.

If you need separate pools per user, have a look at  the 
PerUserPoolDataSource [1] provided by Commons DBCP.

[1] https://s.apache.org/dlghr <https://s.apache.org/dlghr>

Phil

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