MySQL: Transactions across multiple threads

Question

Preliminary:

I have an application which maintains a thread pool of about 100 threads. Each thread can last about 1-30 seconds before a new task re

Answer 1

Sharing connections between lots of threads is usually implemented by using a connection pool. Every thread can request a connection from the pool, use it for its purposes (one or more transactions, committed or rolled back) and hand it back to the pool once the task is finished.

This is what application servers offer you. They will take care of transactions, too, i. e. when the method that requested the transaction finishes normally, changes are committed, if it throws an exception, the database transaction is rolled back.

I suggest you have a look at Java EE 5 or 6 - it is very easy to use and can even be employed in embedded systems. For easy start, have a look at Netbeans and the Glassfish application server. However the general concepts apply to all application servers alike.

As for InnoDB, it will not have any problems handling lots of transactions. Under the supervision of the app server you can concentrate on the business logic and do not have to worry about half-written updates or anyone seeing updates/inserts before the transaction they originate from has been committed.

InnoDB uses MVCC (multi version concurrency control), effectively presenting each transaction with a snapshot of the whole database as of the time when it was started. You can read more about MVCC here in a related question: Question 812512