Assume that we go inside a method and start a transaction in main thread. In this method, there are some async methods so we created 2 more threads inside this method;
Thread 1 --> SubMethod1 --> Saving (t=1)
^
|
MainThread --> MainMethod --> Saving (t=3)
|
v
Thread 2 --> SubMethod2 --> Exception while saving (t=2).
Since thread 2 gets an exception, I want to rollback all transactions done by other threads. However, although transactions owned by main thread an Thread 2 can be roll-backed, I cannot roll-back thread 1 work. I am using Spring/Hibernate, so do you have any idea to manage this and how to apply?
Thanks
Your parent processing thread will (1.) create new threads to do parallel DB inserts, (2.) create a CountDownLatch object (this will hold your parent thread until all child threads which are doing db inserts are finished) (3.) create a db connection object with auto commit mode as FALSE.
Spring uses the underlying database implementation for transactions, so they are as thread safe as the underlying database can be.
The @Transactional annotation is the metadata that specifies the semantics of the transactions on a method. We have two ways to rollback a transaction: declarative and programmatic. In the declarative approach, we annotate the methods with the @Transactional annotation.
Learn more about multi-threading in Spring Boot Using CompletableFuture. Check out this post to learn more about multi-threading in Spring Boot. Multi-threading is similar to multi-tasking, but it enables the processing of executing multiple threads simultaneously, rather than multiple processes.
From Professional Java for Web Applications by Nicholas S. Williams
The transaction scope in Spring is limited to the thread the transaction begins in. The transaction manager then links the transaction to managed resources used in the same thread during the life of the transaction. When using the Java Persistence API, the resource you work with is the EntityManager
. It is the functional equivalent of Hibernate ORM’s Session and JDBC’s Connection. Normally, you would obtain an EntityManager
from the EntityManagerFactory
before beginning a transaction and performing JPA actions. However, this does not work with the Spring Framework model of managing transactions on your behalf. The solution to this problem is the org.springframework.orm.jpa.support.SharedEntityManagerBean
. When you configure JPA in Spring Framework, it creates a SharedEntityManagerBean
that proxies the EntityManager
interface. This proxy is then injected into your JPA repositories. When an EntityManager
method is invoked on this proxy instance, the following happens in the background:
➤➤ If the current thread already has a real EntityManager
with an active transaction, it delegates the call to the method on that EntityManager
.
➤➤ Otherwise, Spring Framework obtains a new EntityManager
from the EntityManagerFactory
, starts a transaction, and binds both to the current thread. It then delegates the call to the method on that EntityManager
. When the transaction is either committed or rolled back, Spring unbinds the transaction and the EntityManager
from the thread and then closes the EntityManager
. Future @Transactional
actions on the same thread (even within the same request) start the process over again, obtaining a new EntityManager
from the factory and beginning a new transaction. This way, no two threads use an EntityManager
at the same time, and a given thread has only one transaction and one EntityManager
active at any given time.
If you were not to use Spring MVC then you would have gotten the session using SessionFactory
in Hibernate. Hibernate Sessions represent the life of a transaction from start to finish. Depending on how your application is architected, that might be less than a second or several minutes; and in a web application, it could be one of several transactions in a request, a transaction lasting an entire request, or a transaction spanning multiple requests. A Session
, which is not thread-safe and must be used only in one thread at a time, is responsible for managing the state of entities.
This post https://dzone.com/articles/spring-transaction-management-over-multiple-thread-1 appears to cover the issue quite well and mentions a project that is doing something similar.
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