HDDS-13586. [DiskBalancer] Refactor DiskBalancer to remove unused methods and improve naming

[Gargi-jais11]

What changes were proposed in this pull request?

1. Improve data structures and type safety :

• In DiskBalancerService, use ContainerID instead of Long for container id.
• Use Objects.requireNonNull(..) instead of Preconditions.checkNotNull(..).
• In DiskBalancerService do not throw RuntimeException instead throw IOException.
• Use StorageVolume.TMP_DIR_NAME to replace DiskBalancerService.DISK_BALANCER_TMP_DIR.
• In DefaultVolumeChoosingPolicy.chooseVolume(..), getCurrentUsage() is called multiple times so it can return different values.

2. Replace the use of Optional for method parameters in DiskBalancer:
As a general rule, parameters should be explicitly required or nullable, not wrapped in an Optional. For context, see: https://www.reddit.com/r/java/comments/sat1j4/opinions_on_using_optional_as_parameter/

3. Cleanup of Dead Code:

• Remove the new Container.importContainerData(Path containerPath) method since it is never used.
• Rename Container.copyContainerData to copyContainerDirectory. As, it sounds like copy/import the ContainerData class.
• SlidingWindow and TestSlidingWindow remove since unused.

4. parameterize disk balancer related unit tests with different container schema versions.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-13586

How was this patch tested?

Passed Existing Tests.

[ChenSammi]

Hi @Gargi-jais11 , it looks like there are a few comments missed to be addressed.

1. Use StorageVolume.TMP_DIR_NAME to replace DiskBalancerService.DISK_BALANCER_TMP_DIR
2. • In DiskBalancerService, use ContainerID instead of Long for container id.
3. • In DefaultVolumeChoosingPolicy.chooseVolume(..), getCurrentUsage() is called multiple times so it can return different values.
4. SlidingWindow and TestSlidingWindow, what's the usage of SlidingWindow here?

[ChenSammi]

Forgot one, parameterize disk balancer related unit tests with different container schema versions.
You can refer to TestBlockDeletingService.java, mainly using "@ContainerTestVersionInfo.ContainerTest" to achieve that.

[Gargi-jais11]

Hi @Gargi-jais11 , it looks like there are a few comments missed to be addressed.

1. Use StorageVolume.TMP_DIR_NAME to replace DiskBalancerService.DISK_BALANCER_TMP_DIR
2. • In DiskBalancerService, use ContainerID instead of Long for container id.
3. • In DefaultVolumeChoosingPolicy.chooseVolume(..), getCurrentUsage() is called multiple times so it can return different values.

Correct. Thank you for pointing out.

4. SlidingWindow and TestSlidingWindow, what's the usage of SlidingWindow here?

Related to this I need to check where it is used.
It seems to be added by me during recent rebase but don't have idea how it got added. I will remove these two classes.

[ChenSammi]

Thanks @Gargi-jais11 .