Fix Stats Collector to not divide by zero

[lucas-a-martins]

Description

Currently, the Stats Collector can throw an arithmetic exception when trying to divide by zero if interval = 0.

This PR fixes this issue by setting the loadHistory.add value to zero when the interval variable is equal to zero.

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)
• build/CI
• test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• Major
• Minor

Screenshots (if appropriate):

How Has This Been Tested?

In debug mode, I tested by setting the interval value to zero. Before the changes, an arithmetic exception was thrown. After the changes, I got no exception and could check that the value added to loadHistory was equal to 0.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 16.00%. Comparing base (b92fd17) to head (eb52f72).
Report is 22 commits behind head on 4.20.

Files with missing lines	Patch %	Lines
...src/main/java/com/cloud/server/StatsCollector.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               4.20   #10492      +/-   ##
============================================
+ Coverage     15.98%   16.00%   +0.01%     
- Complexity    13086    13105      +19     
============================================
  Files          5650     5651       +1     
  Lines        495756   495841      +85     
  Branches      60018    60045      +27     
============================================
+ Hits          79261    79366     +105     
+ Misses       407641   407614      -27     
- Partials       8854     8861       +7     

Flag	Coverage Δ
uitests	4.00% <ø> (-0.01%)	⬇️
unittests	16.84% <0.00%> (+0.02%)	⬆️

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[Pearl1594]

@lucas-a-martins Could you please rebase this off 4.20 - I believe this could be an issue in 4.20 as well.

[Pearl1594]

code lgtm.

[Pearl1594]

@blueorangutan package

[blueorangutan]

@Pearl1594 a [SL] Jenkins job has been kicked to build packages. It will be bundled with KVM, XenServer and VMware SystemVM templates. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ debian ✔️ suse15. SL-JID 12642

[Pearl1594]

After having a conversation with @DaanHoogland on this offline, I understand that reporting a 0 could imply that there were no queries made at all at a specific time, would may not be entirely correct. Having a -1 would indicate an erroneous stats collection for that iteration.

[lucas-a-martins]

@DaanHoogland, @Pearl1594

I applied your suggestions by changing the value to -1 and fixed the maxsize bug. Can you guys take a look?

cc @rohityadavcloud

[DaanHoogland]

@blueorangutan package

[blueorangutan]

@DaanHoogland a [SL] Jenkins job has been kicked to build packages. It will be bundled with KVM, XenServer and VMware SystemVM templates. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ debian ✔️ suse15. SL-JID 12682

[DaanHoogland]

@blueorangutan test keepEnv

[blueorangutan]

@DaanHoogland a [SL] Trillian-Jenkins test job (ol8 mgmt + kvm-ol8) has been kicked to run smoke tests

[blueorangutan]

[SF] Trillian test result (tid-12608)
Environment: kvm-ol8 (x2), Advanced Networking with Mgmt server ol8
Total time taken: 61178 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr10492-t12608-kvm-ol8.zip
Smoke tests completed. 140 look OK, 1 have errors, 0 did not run
Only failed and skipped tests results shown below:

Test	Result	Time (s)	Test File
ContextSuite context=TestSharedNetworkWithConfigDrive>:setup	Error	1521.39	test_network.py

[Pearl1594]

code lgtm

[DaanHoogland]

the refresh fix works. I have no idea how to force the NPE situation (apart from changing the code/core in a debugger. @lucas-a-martins have you seen this happen without debugger?

[lucas-a-martins]

the refresh fix works. I have no idea how to force the NPE situation (apart from changing the code/core in a debugger. @lucas-a-martins have you seen this happen without debugger?

@DaanHoogland only one time and it wasn't in my environment. I don't know how to force it too

[DaanHoogland]

@Pearl1594 , I am fine with merging this, in spite of the corner caaase not being verified. Normal functionality is still working....