Enqueue jobs one by one to the queue can cause the jobs not being executed #1365
Description
Describe the bug
The issue is related to the nature of Helix/ZK and can be reproduced if the user adds jobs in a loop. So if this is the behavior, it is better to do batch job addition. So let's say a user is adding jobs one by one. Let's say the user is job1, job2, and job3.
At T1: Job1 and job2 are added and jobDAG is changed.
At T2: We get children of config and know new configs of job1 and job2 and change in DAG.
At T3: job3 is added and is being added to DAG.
At T4: Refresh is started and the controller sees config of job1, job2 and DAG will be Job1, job2, and job3.
Now in the pipeline, since we see job3 in the DAG and we do not see config, we purge job3 and remove config from ZK. Hence job3 will not be finished at all.
To Reproduce
Add multiple jobs in a loop
Expected behavior
Jobs should be executed and such race conditions should be avoided.