---- On Mon, 15 Mar 2021 11:25:17 -0500 Christopher Schultz <ch...@christopherschultz.net> wrote ----
> Alex, > > On 3/13/21 10:20, My Subs wrote: > > ---- On Fri, 12 Mar 2021 20:24:48 -0500 Christopher Schultz > > <ch...@christopherschultz.net> wrote ---- > > > > > > > > Alex, > > > > > > On 3/12/21 16:32, My Subs wrote: > > > > ---- On Fri, 12 Mar 2021 02:35:27 -0500 Mark Thomas > > <ma...@apache.org> wrote ---- > > > > > > > > > On 12/03/2021 03:57, My Subs wrote: > > > > > > Hello, > > > > > > > > > > > > I'm using Tomcat 10.0.0. Suppose I call setAutoCommit(false) > > on a connection obtained from a Tomcat JDBC Connection Pool. Then I do > > some stuff with the connection, call commit() or rollback() and finally > > call close() on it without ever calling setAutocommit(true). > > > > > > > > > > > > What will the autocommit state of that connection be, the next > > time the pool gives it to my code? Will it be in the same state I left > > it, that is, with autocommit set to false, or will it be reverted back to > > the default state (autocommit set to true)? > > > > > > > > > > The simplest way to be sure is to run a test with a pool size of > > 1. > > > > > > > > > > A quick look at the code (I might have missed something) > > suggests that > > > > > if defaultAutoCommit is configured then it will be reset to that > > default > > > > > value. Otherwise it will be unchanged from when the connection > > was > > > > > returned to the pool. > > > > > > > > > > Mark > > > > > > > > > > > > --------------------------------------------------------------------- > > > > > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > > > > > For additional commands, e-mail: users-h...@tomcat.apache.org > > > > > > > > Hi Mark, > > > > > > > > Thanks for your comment. I found this on > > https://tomcat.apache.org/tomcat-10.0-doc/jdbc-pool.html: > > > > > > > > "The only state the pool itself inserts are defaultAutoCommit, > > defaultReadOnly, defaultTransactionIsolation, defaultCatalog if these are > > set. These 4 properties are only set upon connection creation. Should > > these properties be modified during the usage of the connection, the pool > > itself will not reset them." > > > > > > > > It seems to say that connections will not be reverted back to the > > default auto-commit state even if defaultAutoCommit is set. Given your > > reading of the source code, might it be that the docs are wrong? > > > > > > I think the docs can easily be misunderstood. > > > > > > I don't use the tomcat-pool but I do use the *other* pool provided by > > > Tomcat and they are generally expected to be (mostly) interchangeable. > > > > > > A connection pool which doesn't reset the auto-commit state on > > > connection-return operation would IMO be considered very badly broken. > > > > > > tomcat-pool allows you to NOT specify a default in which case > > > Connection.setAutoCommit() will never be called *at all* by the pool. > > > That seems like reasonable behavior (don't mess with my stuff!), but > > it > > > means that the application will *always* have to reset the auto-commit > > > state to a known value *every single time* a connection is borrowed. > > > > > > Since the whole point of the pool is to manage this kind of thing, I > > > would argue that having defaultAutoCommit NOT set to anything would be > > > considered very bad practice. > > > > > > If you set defaultAutoCommit="true", you should expect that, when your > > > connections are returned to the pool, that setAutoCommit(true) will be > > > called every single time the connection is returned to the pool -- > > > usually by the application calling Connection.close(). > > > > > > Are you worried about a particular use-case or are you just being > > > extra-vigilant? Or are you observing some unexpected behavior? > > > > > > -chris > > > > > > --------------------------------------------------------------------- > > > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > > > For additional commands, e-mail: users-h...@tomcat.apache.org > > > > > > > > > > Hi Chris, > > > > I’m trying to wrap my head around on whether I can end transaction blocks > > in a try clause with a simple call to commit(). That would be the case if > > the pool resets the auto-commit state to the value of defaultAutoCommit. > > Try blocks would end with commit(), catch blocks with rollback(), and the > > pool takes care of setting auto-commit back to true. > > > > On the other hand, if as the docs say, “the pool itself will not reset” > > the state of connection attributes like auto-commit, then I’d need to tack > > to every try/catch a finally clause having setAutoCommit(true). But this > > would be unnecessary boilerplate if, as Mark says —and you believe should > > be the case—, the pool does effect the reset. > > > > I’d rather not bloat the code, hence my question. I guess that puts me in > > the extra-vigilant camp. > > It should work like any other connection pool you have used in the past. > > Just be sure to set defaultAutoCommit="true" in your configuration. Then > it will *always* set autocommit=true when you return your connections to > the pool. > > Just some more food for thought: > https://blog.christopherschultz.net/2009/03/16/properly-handling-pooled-jdbc-connections/ > > > -chris > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > > Hi Chris, Thank you for the advice and the great article. The example it gives on how to prevent partial commits using multiple catch clauses that roll back on every possible exception scenario has me thinking whether all that is necessary when the pool attribute rollbackOnReturn is set to true. I understand that in such case any exception thrown from within a TWR's try block will make TWR to call close() on the connection declared on the TWR header. And given that rollbackOnReturn is set to true, this will make the pool to call rollback() on the connection before returning it to the pool. By the time control reaches any catch clause, the transaction has already been rolled back. Am I missing something and rolling back on the catch clauses is nevertheless necessary? Best, Alex --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
