Different behaviour of MySQL 5.5 and MySQL 5.7 when connection is closed (no replies)

Hi,

I'm not sure what should be correct category where to put my question so I put it to General.

I'm testing MySQL database configured as XA resource in JBoss EAP 6. Running jdbc driver in version 5.1.33.

The scenario which I run is following:
1. start transaction
2. prepare transaction (ie. prepare MySQL db resource)
3. commit transaction (ie. commit MySQL db resource)
4. the message that transaction was commited is not received by transaction manager on JBoss side as at time when MySQL database starts to send the reply the connection is deliberately put down

The behaviour of MySQL 5.5 was that as commit message from JBoss side was received the transaction was commited and data change was reflected in database.
The behavour of MySQL 5.7 is different. Commit message is received but probably (my speculation) as connection is presently closed the transaction is thrown away. The result is that transaction log in database (xa recover;) is empty and data change is not reflected in database.

Do you have some idea what could be behind this behaviour? And do you consider this difference as possible bug which could be raised?

Thank you
Ondra Chaloupka