Hello Chris, Thank you for your reply, but I'm still unsure. You seem to be implying that I have a memory leak, i.e., many connection objects being created that are not being closed. However, I really don't think this is happening. My code closes each connection immediately after using it.
My understanding is that the only way the maximum pool size of X, whatever that is, would be a limitation is if there was an attempt to create X+1 simultaneous connections. When you do this in Glassfish, it outputs an error message saying that no more connections can be created and then crashes. You have to go back in and manually restart it. I believe that the essential problem, as explained in a previous email to Rob Sargent, is that I'm getting several hundred database requests per day from web crawlers. I just spent some time reading through my ngnix access.log and found that the vast majority of these are from GoogleBot. My guess it that, due to a time lag between opening and closing connections, many connections will be opened simultaneously. This is why a small pool size won't work. Also, I'm advised to not block the web crawlers because this assists with SEO. My understanding is that you just have to live with this. I don't think there is an issue with my code. The only answer I can come up with is to have a large maximum pool size, larger that the expected number of simultaneous accesses. I originally wrote to this email list because I was thinking of shifting from Glassfish to Tomcat, and was trying to learn how to do this. I think I do know how to do this now, and might try doing this. My understanding is that the connection pooling that works with Tomcat doesn't have that same limitation as Glassfish, and one can have connections that exist outside the pool. This would resolve the issue I'm currently having with Glassfish. Best regards, Dan Schwartz ---Original Message----- From: Christopher Schultz <ch...@christopherschultz.net> Sent: Thursday, August 7, 2025 2:58 PM To: users@tomcat.apache.org Subject: Re: How to access a REST service Daniel, On 8/5/25 12:43 PM, Daniel Schwartz wrote: > My understanding is that only as many connection objects are created > and placed in the pool as are needed, so even if you set the upper > limit high it doesn’t necessarily mean that you will have that many. This is correct. > Once a database session terminates, then that connection object becomes > available for future use. Correct, as long as we agree on the definition of "database session". In the case of both JDBC and connection pools based upon JDBC connections, the definition of the "end of a session" is "calling Connection.close". If you never call Connection.close, then every connection leaks, and most pools have features to help deal with those circumstances so that badly-written applications don't run out of resources. > So at any given time, the number of connection objects in the pool would be > the maximum number of simultaneous connections that have been made so far, > and not necessarily the total maximum that are allowed (in my case 1000). Is > this correct? More or less, though the pool may grown and shrink slightly around that value. The pool Tomcat uses has features for logging and closing "abandoned connections" which are those which are checked-out of the pool but not properly-returned. I highly recommend enabling those features to investigate what is happening in your environment. Otherwise, your 1000 connections will eventually be exhausted... it will just take much longer than the default 32 where you were observing that behavior. -chris --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
