Fix 1585 - Multiple cumulative metric collections without measurement recording.

[lalitb]

Fixes #1585

Changes

In case cumulative metric collection is done without any measurement recorded in between, the same metrics should be returned. Merge was not happening properly if there is no unreported metrics. This is fixed now. Also added the tests to validate.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #1586 (9d20c60) into main (e27fc88) will increase coverage by 0.11%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1586      +/-   ##
==========================================
+ Coverage   84.96%   85.06%   +0.11%     
==========================================
  Files         156      156              
  Lines        4977     4978       +1     
==========================================
+ Hits         4228     4234       +6     
+ Misses        749      744       -5     

Impacted Files	Coverage Δ
sdk/src/metrics/state/temporal_metric_storage.cc	96.67% <100.00%> (+3.45%)	⬆️
ext/src/http/client/curl/http_client_curl.cc	81.44% <0.00%> (+1.14%)	⬆️

[tauseef-ah]

Hi lalit, I just tested your changes, and I observe the when counter metrics are not sent from application side, then the metrics are displayed as 0. However, when the metrics values are sent the counter correctly accumulates from past data:
{
scope name : ostream_metric_example
schema url :
version : 1.2.0
start time : Thu Sep 1 06:41:35 2022
end time : Thu Sep 1 06:41:36 2022
instrument name : ostream_metric_example
description : description
unit :
type : SumPointData
value : 107
attributes :
resources :
service.name: unknown_service
telemetry.sdk.language: cpp
telemetry.sdk.name: opentelemetry
telemetry.sdk.version: 1.6.0
}
{
scope name : ostream_metric_example
schema url :
version : 1.2.0
start time : Thu Sep 1 06:41:36 2022
end time : Thu Sep 1 06:41:37 2022
instrument name : ostream_metric_example
description : description
unit :
type : SumPointData
value : 0
attributes :
resources :
service.name: unknown_service
telemetry.sdk.language: cpp
telemetry.sdk.name: opentelemetry
telemetry.sdk.version: 1.6.0
}
{
scope name : ostream_metric_example
schema url :
version : 1.2.0
start time : Thu Sep 1 06:41:37 2022
end time : Thu Sep 1 06:41:38 2022
instrument name : ostream_metric_example
description : description
unit :
type : SumPointData
value : 108
attributes :
resources :
service.name: unknown_service
telemetry.sdk.language: cpp
telemetry.sdk.name: opentelemetry
telemetry.sdk.version: 1.6.0
}

[lalitb]

@tauseef-ah - Thanks for testing this. How can I reproduce the scenario?

Record(2) -> Record(3) -> Collect(5) -> Collect(5) -> Record(4) -> Collect(9) -> Collect(9)

I tested something like the above and got the expected result with this PR.

[tauseef-ah]

hi @lalitb , sorry there seems to have been an issue with us picking the wrong binaries at runtime. This solution works fine for us too. Thanks

[ThomsonTan]

Is this jus reformat?

[lalitb]

yes, this is done by clang-format. The only changes are lines 103, and 104 below. To handle the else scenario when there are no measurements recorded since the last collection.