"Number of Connections in Pool" is the number of database connections which will be created. These connections get put in a pool, and each request will grab a connection from the pool, use it, and then put the connection back in to the pool.
"Max Usage For Each Connection" is the maximum number of times that a connection will be used. Once this limit has been hit, the connection will be closed and a new one will be opened to replace it. A large value is probably best, as closing and opening database connections is rather expensive. Some databases and/or JDBC drivers may encounter problems (either functional problems or reduced performance) if you keep the connection open for too many requests though. So you may have to experiment a bit.
I haven't personally tried using the default config elements with a JDBC sampler, but I've heard one or two reports recently that it doesn't work. I've been doing some development with the JDBC sampler recently, so when I get a bit of time I'll take a look at it. It could be a few weeks though...I'm moving at the end of this month, and don't have a lot of spare time right now.
I haven't really noticed the behavior you described where only one active connection is used, but I haven't really been looking out for that kind of issue. So I'd have to check a few things before I could tell you whether it is a bug in JMeter or if it is something else. I'll try to look into that too when I get a chance.
Jeremy http://xirr.com/~jeremy_a
Ryszard Lach wrote:
Hi!
I'm trying to test my postgresql database using jmeter. I have created a
thread group with a couple of (ca. 100) jdbc samplers (under one random
controller). Everything works fine, but I cannot understand what is the
meaning of "Number of Connections in Pool" and "Max Usage For Each
Connection" in "JDBC Database Connection Pool defaults" and in "JDBC
Sampler".
Normally (i.e. with http samplers) one can leave a field blank knowing it will be filled with value defined in default config element, but with JDBC Sampler it doesn't work. Why?
The other thing: I suppose, that setting number of connections to 5 and
max usage to a large value - I will have 5 concurrent connections
between jmeter and database still open and used by testing threads.
Unfortunately, I see one active connection. Thus increasing number of
threads from 5 to 10 - I can not observe bigger load on database server.
Could the random controller be the cause of such a behaviour? All in
all, each single test contains only one (random) request.
Richard.
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