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From Pid <...@pidster.com>
Subject Re: Using Tomcat7 JDBC Connection Pool
Date Thu, 09 Feb 2012 13:35:21 GMT
On 09/02/2012 12:56, amit shah wrote:
> One more comment below about oracle UCP.

<snip>

>>>>> The pool returns members at random, so how would you know which cached
>>>>> credentials you were getting?
>>>>>
>>>>> The credentials which are passed to the getConnection(String username,
>>>> String password) method. When we configure the same pool to be used for
>>>> multiple schema's the pool will *not *be configured with default
>>> username
>>>> password.
>>>
>>> OK, so you create a bunch of connections with various credentials, you
>>> want to cache those connections and only return them if the creds match
>>> for the new request?
>>>
>>> So you're basically creating an uncontrolled pool per cred pair, inside
>>> the outer pool which is controlled?
>>>
>>
>> Yes right.

So why not create multiple controlled pools & not run into availability
problems?


<snip>

>>> What overhead?
>>>
>>
>> The application server and database server resources (memory, cpu etc) for
>> keeping the connections open?

That's a total connection count dependent metric.

So the overhead is virtually the same regardless of whether you have 5
pools or 1, if you have the same total number of connections.


>>> For e.g. If we have 5 tenants with 5
>>>> pools configured with 10 min pool size, we would have min 50 connections
>>>> always open to the database server. This count would be for each
>>>> application server. If we had the same pool for all 5 tenants, there
>>> would
>>>> be just 10 connections open per application server.
>>>
>>> There's a flaw in your logic.
>>>
>>> In your example there may be zero connections open for a given tenant
>>> because they use a shared pool.
>>>
>>> So you might has well have separate pools with the minimum set to 2 and
>>> still have more connections guaranteed per tenant, and the 10 you were
>>> aiming for.
>>>
>>> Worse, if you hit your max with other tenants, a remaining tenant might
>>> not be able to get a connection at all, thus failing to address one of
>>> the key requirements in a multi-tenant system - guaranteed availability.
>>>
>>> Probably true when all the tenants are actively used. As I said, there is
>> always a flexibility in the configuration to use a separate pool for a
>> particular tenant.

That should be the default IMO.  You're asking for trouble otherwise.


>>>> Also the application can always provide a configuration flexibility to
>>>> allow a tenant to use a separate pool instead of sharing it with other
>>>> tenants (like I said above).
>>>>
>>>> This flexibility is provided by the Oracle Universal Connection
>>>> Pool<http://docs.oracle.com/cd/E11882_01/java.112/e12265/toc.htm>
>>>
>>> So if that's a better fit for your requirement, why not use it?
>>>
>>>
> It provides the feature I mentioned about by has lock contention issues.
> Tomcat 7 jdbc pool seems to be better and hence I was trying it out.

!

<snip>

>>> If you are programmatically registering the pool, can you not just
>>> register it with the MBean server yourself?
>>>
>>> Ok I will try this and provide an update.

Cool.


p




-- 

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