Add/enhance various log lines in order to improve debuggability

Author: Przemyslaw Witek

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/utils/MlIndexAndAlias.java

@@ -132,6 +132,7 @@ private static void createFirstConcreteIndex(Client client,
                                                  String alias,
                                                  boolean addAlias,
                                                  ActionListener<Boolean> listener) {
+        logger.info("About to create first concrete index [{}] with alias [{}]", index, alias);
         CreateIndexRequestBuilder requestBuilder = client.admin()
             .indices()
             .prepareCreate(index);
@@ -163,6 +164,7 @@ private static void updateWriteAlias(Client client,
                                          @Nullable String currentIndex,
                                          String newIndex,
                                          ActionListener<Boolean> listener) {
+        logger.info("About to move write alias [{}] from index [{}] to index [{}]", alias, currentIndex, newIndex);
         IndicesAliasesRequestBuilder requestBuilder = client.admin()
             .indices()
             .prepareAliases()

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/action/TransportStartDataFrameAnalyticsAction.java

@@ -643,9 +643,9 @@ public PersistentTasksCustomMetadata.Assignment getAssignment(StartDataFrameAnal
         @Override
         protected void nodeOperation(AllocatedPersistentTask task, StartDataFrameAnalyticsAction.TaskParams params,
                                      PersistentTaskState state) {
-            logger.info("[{}] Starting data frame analytics", params.getId());
             DataFrameAnalyticsTaskState analyticsTaskState = (DataFrameAnalyticsTaskState) state;
             DataFrameAnalyticsState analyticsState = analyticsTaskState == null ? null : analyticsTaskState.getState();
+            logger.info("[{}] Starting data frame analytics from state [{}]", params.getId(), analyticsState);
 
             // If we are "stopping" there is nothing to do and we should stop
             if (DataFrameAnalyticsState.STOPPING.equals(analyticsState)) {

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/dataframe/process/AnalyticsProcessManager.java

@@ -11,7 +11,6 @@
 import org.apache.lucene.util.SetOnce;
 import org.elasticsearch.action.admin.indices.refresh.RefreshAction;
 import org.elasticsearch.action.admin.indices.refresh.RefreshRequest;
-import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.client.Client;
@@ -267,10 +266,6 @@ private void writeHeaderRecord(DataFrameDataExtractor dataExtractor, AnalyticsPr
         process.writeRecord(headerRecord);
     }
 
-    private void indexDataCounts(DataCounts dataCounts) {
-        IndexRequest indexRequest = new IndexRequest(MlStatsIndex.writeAlias());
-    }
-
     private void restoreState(DataFrameAnalyticsTask task, DataFrameAnalyticsConfig config, @Nullable BytesReference state,
                               AnalyticsProcess<AnalyticsResult> process) {
         if (config.getAnalysis().persistsState() == false) {

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/TrainedModelStatsService.java

@@ -105,6 +105,7 @@ public void queueStats(InferenceStats stats) {
     }
 
     void stop() {
+        logger.info("About to stop TrainedModelStatsService");
         stopped = true;
         statsQueue.clear();
 
@@ -115,6 +116,7 @@ void stop() {
     }
 
     void start() {
+        logger.info("About to start TrainedModelStatsService");
         stopped = false;
         scheduledFuture = threadPool.scheduleWithFixedDelay(this::updateStats,
             PERSISTENCE_INTERVAL,
@@ -126,11 +128,13 @@ void updateStats() {
             return;
         }
         if (verifiedStatsIndexCreated == false) {
+            logger.info("About to create the stats index as it does not exist yet");
             try {
                 PlainActionFuture<Boolean> listener = new PlainActionFuture<>();
                 MlStatsIndex.createStatsIndexAndAliasIfNecessary(client, clusterState, indexNameExpressionResolver, listener);
                 listener.actionGet();
                 verifiedStatsIndexCreated = true;
+                logger.info("Created stats index");
             } catch (Exception e) {
                 logger.error("failure creating ml stats index for storing model stats", e);
                 return;