Check pending requests runs in an infinite loop

[robbynshaw]

Describe the bug
As soon as kafkajs initiates a connection to a Kafka cluster, requestQueue.fullfillRequest is hit which begins an infinite loop in the RequestQueue of the checkPendingRequests command. This is due to the fact that checkPendingRequests schedules a new check every time it finishes, regardless of whether or not any requests are pending.

In addition, the scheduleAt parameter for the next check is set to a negative value by default, so the scheduled check runs immediately, and then the cycle starts again. This results in the process running as fast as your little CPU can handle.

In a bare setup, this does not result in any real issue, it simply consumes a lot of cycles without any benefit (AFAIK). However, if you are using the newrelic package to monitor your code, it will shim setTimeout during an transaction and create a SegmentTrace object. As there are thousands of these being created, if the transaction continues, you will quickly run out of memory in your Node heap or your server.

To Reproduce
Link to PR with failing tests: #1703
Failing test output: https://github.com/tulios/kafkajs/pull/1703/checks?check_run_id=27018283006
Shows that within one second, upon initial connection, this method is hit 694 times.

Note: Code for a fix is commented out in the PR.

Expected behavior
checkPendingRequests should only be run when there are pending requests possible. If nothing has been throttled or queued up, there is no reason to re-run this code, as pushing a new message will still flush the queue appropriately.

Observed behavior
Infinite loop. See above.

Environment:

• OS: verified on Ubuntu and RHEL
• KafkaJS version 2.2.4
• Kafka version 3.4.0
• NodeJS version 18.16.0