[Branch-2.7] Fix ledger roll over scheduler task

[gaoran10]

The PR #11116 couldn't be cherry-picked to branch-2.7, because there are too many conflicts.

In PR #8946 the ledger rollover task had been moved from BrokerService to ManagedLedgerImpl, and this PR is based on it.

Motivation

Currently, the ledger rollover scheduled task will execute before reach the ledger maximum rollover time, this will cause the ledger doesn't roll over in time.

Modifications

Only make the ledger rollover scheduled task after the ledger created successfully.
If the scheduled task was executed when there is no entry in the current ledger, the scheduled task will not be re-executed, and if there is new entry is added the ledger will rollover.

Verifying this change

Add a unit test to verify the ledger could be rolled over in time.

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (no)
• The public API: (no)
• The schema: (no)
• The default values of configurations: (no)
• The wire protocol: (no)
• The rest endpoints: (no)
• The admin cli options: (no)
• Anything that affects deployment: (no)

[eolivelli]

overall the change looks good to me.

but I am afraid that we are adding a new flaky test

can you please check my comment ?

[eolivelli]

I am not sure that on CI we can rely on making the difference in the order of 100ms

it is possible that the machine is very slow and then we will see the test failing

[gaoran10]

Yes, I'll increase the time order of magnitude, we could set the maximum rollover time to 10 seconds and wait 11 seconds? Maybe 1 second is more stable?

[eolivelli]

let's try

@lhotari what do you think ?

[lhotari]

In general, I think it's better not to test accurate timings. The test code is cleaner when .atMost is omitted. The default value is 10 seconds and that should be suitable for most cases where the operation is expected to complete in less than 10 seconds.