Fix index not found reported as server error bug

[dai-chen]

Description

IndexNotFoundException thrown from OpenSearch get index mapping API is treated as server error. This caused breaking behavior as reported in issue below. More importantly, this may cause false alarm if monitoring logic on SQL plugin.

Root Cause

Due to security concern, we switched from OpenSearch's ClusterService.getIndexMapping() to our current OpenSearchNodeClient.getIndexMapping(). OpenSearchNodeClient captures every exception thrown from underlying OpenSearch API, including IndexNotFoundException, and wrap it by IllegalStateException. On the high level, isClientError() determines if this is a client error on IllegalStateException instead of the IndexNotFoundException wrapped inside.

Quick Fix

1. Capture IndexNotFoundException individually and re-throw it directly to fix the issue
2. Add IT in PPLPluginIT because no better place in SQL IT. Confirmed it can reproduce the issue without the fix
3. Clean up the unused resolver field and mockNodeClient() handy

Issues Resolved

#851

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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[Yury-Fridlyand]

Maybe add an integration test which proves the fix in the end-to-end flow?

[dai-chen]

Maybe add an integration test which proves the fix in the end-to-end flow?

Yes, just found a place to add it.

[codecov-commenter]

Codecov Report

Merging #1353 (911c769) into main (114e02a) will increase coverage by 0.00%.
The diff coverage is 100.00%.

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@@            Coverage Diff            @@
##               main    #1353   +/-   ##
=========================================
  Coverage     98.38%   98.38%           
  Complexity     3693     3693           
=========================================
  Files           343      343           
  Lines          9106     9107    +1     
  Branches        585      585           
=========================================
+ Hits           8959     8960    +1     
  Misses          142      142           
  Partials          5        5           

Flag	Coverage Δ
sql-engine	98.38% <100.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
...ch/sql/opensearch/client/OpenSearchNodeClient.java	100.00% <100.00%> (ø)

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