[Bugfix] Fix IllegalArgumentException thrown when creating a PIT

CHANGELOG.md

@@ -62,6 +62,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Tiered Caching] Fix bug in cache stats API ([#16560](https://github.com/opensearch-project/OpenSearch/pull/16560))
 - Bound the size of cache in deprecation logger ([16702](https://github.com/opensearch-project/OpenSearch/issues/16702))
 - Ensure consistency of system flag on IndexMetadata after diff is applied ([#16644](https://github.com/opensearch-project/OpenSearch/pull/16644))
+- Fix illegal argument exception when creating a PIT ([#16781](https://github.com/opensearch-project/OpenSearch/pull/16781))
 
 ### Security
 

server/src/main/java/org/opensearch/action/search/SearchRequestStats.java

@@ -73,20 +73,32 @@ public long getTookMetric() {
 
     @Override
     protected void onPhaseStart(SearchPhaseContext context) {
-        phaseStatsMap.get(context.getCurrentPhase().getSearchPhaseName()).current.inc();
+        try {
+            phaseStatsMap.get(context.getCurrentPhase().getSearchPhaseName()).current.inc();
+        } catch (IllegalArgumentException ignored) {
+            // Do nothing if the phase isn't found in SearchPhaseName.
+        }
     }
 
     @Override
     protected void onPhaseEnd(SearchPhaseContext context, SearchRequestContext searchRequestContext) {
-        StatsHolder phaseStats = phaseStatsMap.get(context.getCurrentPhase().getSearchPhaseName());
-        phaseStats.current.dec();
-        phaseStats.total.inc();
-        phaseStats.timing.inc(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - context.getCurrentPhase().getStartTimeInNanos()));
+        try {
+            StatsHolder phaseStats = phaseStatsMap.get(context.getCurrentPhase().getSearchPhaseName());
+            phaseStats.current.dec();
+            phaseStats.total.inc();
+            phaseStats.timing.inc(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - context.getCurrentPhase().getStartTimeInNanos()));
+        } catch (IllegalArgumentException ignored) {
+            // Do nothing if the phase isn't found in SearchPhaseName.
+        }
     }
 
     @Override
     protected void onPhaseFailure(SearchPhaseContext context, Throwable cause) {
-        phaseStatsMap.get(context.getCurrentPhase().getSearchPhaseName()).current.dec();
+        try {
+            phaseStatsMap.get(context.getCurrentPhase().getSearchPhaseName()).current.dec();
+        } catch (IllegalArgumentException ignored) {
+            // Do nothing if the phase isn't found in SearchPhaseName.
+        }
     }
 
     @Override

server/src/test/java/org/opensearch/action/search/SearchRequestStatsTests.java

@@ -205,4 +205,25 @@ public void testSearchRequestStatsOnPhaseFailureConcurrently() throws Interrupte
             assertEquals(0, testRequestStats.getPhaseCurrent(searchPhaseName));
         }
     }
+
+    public void testOtherPhaseNamesAreIgnored() {
+        // Unrecognized phase names shouldn't be tracked, but should not throw any error.
+        ClusterSettings clusterSettings = new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS);
+        SearchRequestStats testRequestStats = new SearchRequestStats(clusterSettings);
+        SearchPhaseContext ctx = mock(SearchPhaseContext.class);
+        SearchPhase mockSearchPhase = new SearchPhase("unrecognized_phase") {
+            @Override
+            public void run() {}
+        };
+        when(ctx.getCurrentPhase()).thenReturn(mockSearchPhase);
+        testRequestStats.onPhaseStart(ctx);
+        testRequestStats.onPhaseEnd(
+            ctx,
+            new SearchRequestContext(
+                new SearchRequestOperationsListener.CompositeListener(List.of(), LogManager.getLogger()),
+                new SearchRequest(),
+                () -> null
+            )
+        );
+    }
 }