Fixed the bug in CacheConfigMetricsCollector (#657) (#661)

* Fixed the bug in CacheConfigMetricsCollector

Signed-off-by: Atharva Sharma <atharvasharma61@gmail.com>

* Fixes error logging

Signed-off-by: Gagan Juneja <gjjuneja@amazon.com>

---------

Signed-off-by: Atharva Sharma <atharvasharma61@gmail.com>
Signed-off-by: Gagan Juneja <gjjuneja@amazon.com>
Co-authored-by: Gagan Juneja <gjjuneja@amazon.com>
(cherry picked from commit 489f318)

Co-authored-by: Atharva Sharma <60044988+atharvasharma61@users.noreply.github.com>

src/main/java/org/opensearch/performanceanalyzer/collectors/CacheConfigMetricsCollector.java

@@ -17,6 +17,8 @@
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import org.apache.commons.lang3.reflect.FieldUtils;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.opensearch.common.cache.Cache;
 import org.opensearch.indices.IndicesService;
 import org.opensearch.performanceanalyzer.OpenSearchResources;
@@ -43,6 +45,7 @@ public class CacheConfigMetricsCollector extends PerformanceAnalyzerMetricsColle
         implements MetricsProcessor {
     public static final int SAMPLING_TIME_INTERVAL =
             MetricsConfiguration.CONFIG_MAP.get(CacheConfigMetricsCollector.class).samplingInterval;
+    private static final Logger LOG = LogManager.getLogger(CacheConfigMetricsCollector.class);
     private static final int KEYS_PATH_LENGTH = 0;
     private StringBuilder value;
 
@@ -104,10 +107,14 @@ public void collectMetrics(long startTime) {
                                                         indicesService,
                                                         "indicesRequestCache",
                                                         true);
+                                        Object openSearchOnHeapCache =
+                                                FieldUtils.readField(reqCache, "cache", true);
                                         Cache requestCache =
                                                 (Cache)
                                                         FieldUtils.readField(
-                                                                reqCache, "cache", true);
+                                                                openSearchOnHeapCache,
+                                                                "cache",
+                                                                true);
                                         Long requestCacheMaxSize =
                                                 (Long)
                                                         FieldUtils.readField(
@@ -118,10 +125,15 @@ public void collectMetrics(long startTime) {
                                                 SHARD_REQUEST_CACHE.toString(),
                                                 requestCacheMaxSize);
                                     } catch (Exception e) {
-                                        return new CacheMaxSizeStatus(
-                                                SHARD_REQUEST_CACHE.toString(), null);
+                                        LOG.error("Error while evaluating requestCacheMaxSize", e);
+                                        return null;
                                     }
                                 });
+
+        if (shardRequestCacheMaxSizeStatus == null) {
+            return;
+        }
+
         value.append(PerformanceAnalyzerMetrics.sMetricNewLineDelimitor)
                 .append(shardRequestCacheMaxSizeStatus.serialize());
         saveMetricValues(value.toString(), startTime);