Handle negative search request nodes stats

[dzane17]

Description

We identified a bug where negative search stats are causing an exception when processed using VLong in the following line:

https://github.com/opensearch-project/OpenSearch/blob/main/server/src/main/java/org/opensearch/index/search/stats/SearchStats.java#L89

out.writeVLong(current);

The issue occurs because the VLong is used as a counter for tracking number of active phases. However, since there can be multiple paths for exiting a phase, the counters can be decremented more than once.

Solution

Check for negative values before read/write using VLong. If negative, write 0 instead.

I explored using ZLong, but this can cause serde issues between different OpenSearch versions.

Related Issues

Resolves #16598

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❌ Gradle check result for 6560f5e: FAILURE

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❌ Gradle check result for 751d5ac: null

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❌ Gradle check result for ed3c69e: FAILURE

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❌ Gradle check result for 65b5bc9: FAILURE

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[jainankitk]

Ideally we should fix the issue of negative stats itself, but node should not be going down due to serialization issue, so LGTM!

[jainankitk]

The test failures look related to me. I am wondering if this can break backward compatibility is some way:

[Test Result](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/) (14 failures / +14)

    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/10_basic/Nodes stats}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_10_basic_Nodes_stats_/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/20_response_filtering/Nodes Stats filtered using both includes and excludes filters}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_20_response_filtering_Nodes_Stats_filtered_using_both_includes_and_excludes_filters_/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/20_response_filtering/Nodes Stats with response filtering}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_20_response_filtering_Nodes_Stats_with_response_filtering_/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/11_indices_metrics/Metric - _all include_segment_file_sizes}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_11_indices_metrics_Metric____all_include_segment_file_sizes_/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/11_indices_metrics/Metric - indices _all}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_11_indices_metrics_Metric___indices__all_/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/10_basic/Nodes stats}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_10_basic_Nodes_stats__2/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/20_response_filtering/Nodes Stats with response filtering}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_20_response_filtering_Nodes_Stats_with_response_filtering__2/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/11_indices_metrics/Metric - _all include_segment_file_sizes}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_11_indices_metrics_Metric____all_include_segment_file_sizes__2/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/10_basic/Nodes stats}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_10_basic_Nodes_stats__3/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/20_response_filtering/Nodes Stats with response filtering}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_20_response_filtering_Nodes_Stats_with_response_filtering__3/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/11_indices_metrics/Metric - _all include_segment_file_sizes}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_11_indices_metrics_Metric____all_include_segment_file_sizes__3/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/10_basic/Nodes stats}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_10_basic_Nodes_stats__4/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/20_response_filtering/Nodes Stats with response filtering}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_20_response_filtering_Nodes_Stats_with_response_filtering__4/)
    [org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=nodes.stats/11_indices_metrics/Metric - _all include_segment_file_sizes}](https://build.ci.opensearch.org/job/gradle-check/64475/testReport/junit/org.opensearch.backwards/MixedClusterClientYamlTestSuiteIT/test__p0_nodes_stats_11_indices_metrics_Metric____all_include_segment_file_sizes__4/)

[github-actions]

❌ Gradle check result for 092cb9d: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[dzane17]

@jainankitk @sgup432 I revised the solution to avoid serde issues. No longer using ZLong

[github-actions]

✅ Gradle check result for cbc5507: SUCCESS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.92%. Comparing base (b4583c3) to head (8e664f8).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #19340      +/-   ##
============================================
- Coverage     72.96%   72.92%   -0.04%     
- Complexity    70117    70125       +8     
============================================
  Files          5687     5687              
  Lines        321659   321669      +10     
  Branches      46525    46527       +2     
============================================
- Hits         234684   234587      -97     
- Misses        68041    68171     +130     
+ Partials      18934    18911      -23     

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[github-actions]

❌ Gradle check result for fb422fd: TIMEOUT

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[github-actions]

❕ Gradle check result for 8e664f8: UNSTABLE

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.