[HIVE-24363] Current order of transactional event listeners is prone to deadlock in backend DB connections

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Labels: pull-request-available
• Assignee: Pravin Sinha
• Reporter: Pravin Sinha
• Created: 10/Nov/20 04:35
• Updated: 19/Jan/21 01:32
• Resolved: 12/Nov/20 12:01

Description

Currently the AcidEventListener is added to the end of list of transactional event listeners. When DbNotificationListener is configured as 'hive.metastore.transactional.event.listeners'. The final list will be formed as :

{"DbNotificationListener" , "AcidEventListener"}

This will result in backend DB lock acquisition in this order:

 lock(a) {
        // perform some op on a
        lock(b) {
          // perform some op on b
        }
  }

On the other hand, there are some HMS API say for example commit_txn(), which calls the TxnHandler method directly, followed by DbNotificationListener processing. Which will result in the lock acquisition in reverse order:

lock(b) {
    // perform some op on b        
    lock(a) {
        // perform some op on a
    }   
 }

Note: 'a' and 'b' above are backend  DB lock and not jvm locks.

Issue Links

• links to: GitHub Pull Request #1657