Hikari connection pool with oracle on azure

Question

We are using Hikari Connection pool to connect to Oracle on Azure. We tried increasing the timeout value to 12000000 after consecutive connection time out error with a value 600000.

Error is intermittent

2022-04-06 08:32:18 java.lang.Exception: Error while getting connection 
from connection pool for:#### Connection is not available, request 
timed out after 300001ms.

What ever be the time we get this error intermittently.

Answer 1

Connection is not available, request timed out after 300001ms.

As suggested by brettwooldridge, adding gist as a community wiki answer to help other community members who might face the similar issue.

The connection timeout issue could be due to multiple reasons:

• The application or database server CPUs are overloaded and pegged at 100% for more than 30 seconds.
• The server is a virtual machine, and the VM was suspended for more than 30 seconds.
• The application has some long-running queries (> 30 seconds).
• The number of application threads vastly outnumbers the maximumPoolSize combined with somewhat slow queries.