diff --git a/alerting/build.gradle b/alerting/build.gradle
index dc42cd126..5ca3c6ec0 100644
--- a/alerting/build.gradle
+++ b/alerting/build.gradle
@@ -92,6 +92,8 @@ dependencies {
 
     testImplementation "org.jetbrains.kotlin:kotlin-test:${kotlin_version}"
     testImplementation "org.mockito:mockito-core:4.7.0"
+    testImplementation "org.opensearch.plugin:reindex-client:${opensearch_version}"
+    testImplementation "org.opensearch.plugin:parent-join-client:${opensearch_version}"
 }
 
 javadoc.enabled = false // turn off javadoc as it barfs on Kotlin code
diff --git a/alerting/src/main/kotlin/org/opensearch/alerting/DocumentLevelMonitorRunner.kt b/alerting/src/main/kotlin/org/opensearch/alerting/DocumentLevelMonitorRunner.kt
index 787f2371c..ee31fe1a3 100644
--- a/alerting/src/main/kotlin/org/opensearch/alerting/DocumentLevelMonitorRunner.kt
+++ b/alerting/src/main/kotlin/org/opensearch/alerting/DocumentLevelMonitorRunner.kt
@@ -6,6 +6,7 @@
 package org.opensearch.alerting
 
 import org.apache.logging.log4j.LogManager
+import org.opensearch.ExceptionsHelper
 import org.opensearch.action.admin.indices.get.GetIndexRequest
 import org.opensearch.action.admin.indices.get.GetIndexResponse
 import org.opensearch.action.index.IndexRequest
@@ -173,14 +174,17 @@ object DocumentLevelMonitorRunner : MonitorRunner() {
                     }
                 }
             }
+            monitorResult = monitorResult.copy(inputResults = InputRunResults(listOf(inputRunResults)))
         } catch (e: Exception) {
-            logger.error("Failed to start Document-level-monitor $index. Error: ${e.message}", e)
-            val alertingException = AlertingException.wrap(e)
-            return monitorResult.copy(error = alertingException, inputResults = InputRunResults(emptyList(), alertingException))
+            logger.error("Failed to start Document-level-monitor ${monitor.name}", e)
+            val alertingException = AlertingException(
+                ExceptionsHelper.unwrapCause(e).cause?.message.toString(),
+                RestStatus.INTERNAL_SERVER_ERROR,
+                e
+            )
+            monitorResult = monitorResult.copy(error = alertingException, inputResults = InputRunResults(emptyList(), alertingException))
         }
 
-        monitorResult = monitorResult.copy(inputResults = InputRunResults(listOf(inputRunResults)))
-
         /*
          populate the map queryToDocIds with pairs of <DocLevelQuery object from queries in monitor metadata &
          list of matched docId from inputRunResults>
@@ -531,15 +535,46 @@ object DocumentLevelMonitorRunner : MonitorRunner() {
         return hits.map { hit ->
             val sourceMap = hit.sourceAsMap
 
-            var xContentBuilder = XContentFactory.jsonBuilder().startObject()
-            sourceMap.forEach { (k, v) ->
-                xContentBuilder = xContentBuilder.field("${k}_${index}_$monitorId", v)
-            }
-            xContentBuilder = xContentBuilder.endObject()
+            transformDocumentFieldNames(sourceMap, "_${index}_$monitorId")
+
+            var xContentBuilder = XContentFactory.jsonBuilder().map(sourceMap)
 
             val sourceRef = BytesReference.bytes(xContentBuilder)
 
+            logger.debug("Document [${hit.id}] payload after transform: ", sourceRef.utf8ToString())
+
             Pair(hit.id, sourceRef)
         }
     }
+
+    /**
+     * Traverses document fields in leaves recursively and appends [fieldNameSuffix] to field names.
+     *
+     * Example for index name is my_log_index and Monitor ID is TReewWdsf2gdJFV:
+     * {                         {
+     *   "a": {                     "a": {
+     *     "b": 1234      ---->       "b_my_log_index_TReewWdsf2gdJFV": 1234
+     *   }                          }
+     * }
+     *
+     * @param jsonAsMap               Input JSON (as Map)
+     * @param fieldNameSuffix         Field suffix which is appended to existing field name
+     */
+    private fun transformDocumentFieldNames(
+        jsonAsMap: MutableMap<String, Any>,
+        fieldNameSuffix: String
+    ) {
+        val tempMap = mutableMapOf<String, Any>()
+        val it: MutableIterator<Map.Entry<String, Any>> = jsonAsMap.entries.iterator()
+        while (it.hasNext()) {
+            val entry = it.next()
+            if (entry.value is Map<*, *>) {
+                transformDocumentFieldNames(entry.value as MutableMap<String, Any>, fieldNameSuffix)
+            } else if (entry.key.endsWith(fieldNameSuffix) == false) {
+                tempMap["${entry.key}$fieldNameSuffix"] = entry.value
+                it.remove()
+            }
+        }
+        jsonAsMap.putAll(tempMap)
+    }
 }