kvm: remove unnecessary new String

[ustcweizhou]

Description

Thanks @rubieHess to point it out.
see #4800 (comment)

I detect that this code is problematic. According to the Performance (PERFORMANCE), Dm: Method invokes inefficient new String(String) constructor (DM_STRING_CTOR).
Using the java.lang.String(String) constructor wastes memory because the object so constructed will be functionally indistinguishable from the String passed as a parameter.  Just use the argument String directly.

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• Major
• Minor

Bug Severity

• BLOCKER
• Critical
• Major
• Minor
• Trivial

Screenshots (if appropriate):

How Has This Been Tested?

[GabrielBrascher]

Thanks for this PR, @ustcweizhou. I am +1 on removing the String constructors, they should be avoided indeed.

I would also suggest externalizing them to constants, what do you think?

In terms of performance, I think that it does not change much being a constant or not. The way you are doing the String object is created only once. Java will detect the duplicated Strings in runtime and reuse them from the String's constant pool.

However, constants help code maintainability and readability. Especially on the duplicated Strings where a developer can easily change all occurrences by simply altering the constant.

[weizhouapache]

Thanks for this PR, @ustcweizhou. I am +1 on removing the String constructors, they should be avoided indeed.

I would also suggest externalizing them to constants, what do you think?

In terms of performance, I think that it does not change much being a constant or not. The way you are doing the String object is created only once. Java will detect the duplicated Strings in runtime and reuse them from the String's constant pool.

However, constants help code maintainability and readability. Especially on the duplicated Strings where a developer can easily change all occurrences by simply altering the constant.

@GabrielBrascher
agree. I will update this pr.

[yadvr]

@blueorangutan package

[blueorangutan]

@rhtyd a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result: ✔️ centos7 ✔️ centos8 ✖️ debian. SL-JID 280

[yadvr]

@blueorangutan test

[blueorangutan]

@rhtyd a Trillian-Jenkins test job (centos7 mgmt + kvm-centos7) has been kicked to run smoke tests

[blueorangutan]

Trillian test result (tid-285)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 46496 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr4870-t285-kvm-centos7.zip
Intermittent failure detected: /marvin/tests/smoke/test_affinity_groups_projects.py
Intermittent failure detected: /marvin/tests/smoke/test_affinity_groups.py
Intermittent failure detected: /marvin/tests/smoke/test_kubernetes_clusters.py
Intermittent failure detected: /marvin/tests/smoke/test_privategw_acl.py
Intermittent failure detected: /marvin/tests/smoke/test_vpc_redundant.py
Intermittent failure detected: /marvin/tests/smoke/test_vpc_router_nics.py
Intermittent failure detected: /marvin/tests/smoke/test_hostha_kvm.py
Smoke tests completed. 81 look OK, 5 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File
test_DeployVmAntiAffinityGroup_in_project	Error	63.57	test_affinity_groups_projects.py
test_DeployVmAntiAffinityGroup	Error	41.98	test_affinity_groups.py
test_04_deploy_and_scale_kubernetes_cluster	Failure	23.21	test_kubernetes_clusters.py
test_07_deploy_kubernetes_ha_cluster	Failure	0.04	test_kubernetes_clusters.py
test_08_deploy_and_upgrade_kubernetes_ha_cluster	Failure	0.04	test_kubernetes_clusters.py
test_09_delete_kubernetes_ha_cluster	Failure	0.04	test_kubernetes_clusters.py
ContextSuite context=TestKubernetesCluster>:teardown	Error	60.13	test_kubernetes_clusters.py
test_04_rvpc_network_garbage_collector_nics	Failure	326.07	test_vpc_redundant.py
test_hostha_kvm_host_degraded	Failure	677.61	test_hostha_kvm.py
test_hostha_kvm_host_fencing	Failure	642.08	test_hostha_kvm.py
test_hostha_kvm_host_recovering	Failure	643.95	test_hostha_kvm.py

[DaanHoogland]

pl wait with merging @rhtyd , I think @weizhouapache wants to externalise those strings to constants as well.

[Pearl1594]

@blueorangutan package

[blueorangutan]

@Pearl1594 a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result: ✔️ centos7 ✖️ centos8 ✔️ debian. SL-JID 295

[GabrielBrascher]

Thanks for the updates, @ustcweizhou.
Code LGTM.

[yadvr]

@blueorangutan test

[blueorangutan]

@rhtyd a Trillian-Jenkins test job (centos7 mgmt + kvm-centos7) has been kicked to run smoke tests

[blueorangutan]

Trillian test result (tid-324)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 40567 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr4870-t324-kvm-centos7.zip
Intermittent failure detected: /marvin/tests/smoke/test_kubernetes_clusters.py
Intermittent failure detected: /marvin/tests/smoke/test_vm_life_cycle.py
Intermittent failure detected: /marvin/tests/smoke/test_vpc_redundant.py
Smoke tests completed. 84 look OK, 2 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File
ContextSuite context=TestKubernetesCluster>:teardown	Error	69.81	test_kubernetes_clusters.py
test_01_migrate_VM_and_root_volume	Error	69.20	test_vm_life_cycle.py
test_02_migrate_VM_with_two_data_disks	Error	49.03	test_vm_life_cycle.py

[DaanHoogland]

great work once a gain @weizhouapache. ok to merge @rhtyd / @shwstppr ?