Fix exceptions in IntervalCalculation and ResultIndexingHandler

[kaituo]

Description

• IntervalCalculation: Prevent an ArrayIndexOutOfBoundsException by returning early when there are fewer than two timestamps. Previously, the code assumed at least two timestamps, causing an exception when only one was present.

• ResultIndexingHandler: Handle exceptions from asynchronous calls by logging error messages instead of throwing exceptions. Since the caller does not wait for these asynchronous operations, throwing exceptions had no effect and could lead to unhandled exceptions. Logging provides visibility without disrupting the caller's flow.

Testing done:

1. added UT and ITs.

Signed-off-by: Kaituo Li [email protected]

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

Attention: Patch coverage is 97.14286% with 1 line in your changes missing coverage. Please review.

Project coverage is 81.61%. Comparing base (1a3b8c9) to head (b85e825).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...eries/transport/handler/ResultIndexingHandler.java	96.96%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1379      +/-   ##
============================================
+ Coverage     80.11%   81.61%   +1.50%     
- Complexity     5710     5826     +116     
============================================
  Files           533      533              
  Lines         23527    23522       -5     
  Branches       2367     2367              
============================================
+ Hits          18848    19197     +349     
+ Misses         3557     3167     -390     
- Partials       1122     1158      +36     

Flag	Coverage Δ
plugin	81.61% <97.14%> (+1.50%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...t/transport/ForecastResultBulkTransportAction.java	48.14% <ø> (ø)
...h/timeseries/rest/handler/IntervalCalculation.java	93.20% <100.00%> (ø)
...eries/transport/handler/ResultIndexingHandler.java	86.25% <96.96%> (+21.54%)	⬆️

... and 28 files with indirect coverage changes

[owaiskazi19]

Took an initial pass

[owaiskazi19]

LG

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/anomaly-detection/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/anomaly-detection/backport-2.x
# Create a new branch
git switch --create backport/backport-1379-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 0adf906017229fc11498c3307237e4ee6bd6ca8c
# Push it to GitHub
git push --set-upstream origin backport/backport-1379-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/anomaly-detection/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-1379-to-2.x.