[ML] Correctly collect datafeed stats for _all (elastic/x-pack-elasticsearch#776)

Datafeed state was always stopped when the stats
endpoint was called with _all. The reason is that
_all was not being expanded into all datafeed IDs.

This commit fixes the issue by expanding _all into
all datafeed IDs in the cluster. Stats are then fetched
for all of them.

relates elastic/x-pack-elasticsearch#693

Original commit: elastic/x-pack-elasticsearch@ccbdb35b6e

plugin/src/main/java/org/elasticsearch/xpack/ml/action/GetDatafeedsStatsAction.java

@@ -43,9 +43,12 @@ import org.elasticsearch.xpack.persistent.PersistentTasks.PersistentTask;
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.stream.Collectors;
 
 public class GetDatafeedsStatsAction extends Action<GetDatafeedsStatsAction.Request, GetDatafeedsStatsAction.Response,
         GetDatafeedsStatsAction.RequestBuilder> {
@@ -299,32 +302,42 @@ public class GetDatafeedsStatsAction extends Action<GetDatafeedsStatsAction.Requ
         }
 
         @Override
-        protected void masterOperation(Request request, ClusterState state, ActionListener<Response> listener) throws Exception {
+        protected void masterOperation(Request request, ClusterState state,
+                                       ActionListener<Response> listener) throws Exception {
             logger.debug("Get stats for datafeed '{}'", request.getDatafeedId());
 
-            Map<String, DatafeedStats> results = new HashMap<>();
             MlMetadata mlMetadata = state.metaData().custom(MlMetadata.TYPE);
-            PersistentTasks tasksInProgress = state.getMetaData().custom(PersistentTasks.TYPE);
+
-            if (request.getDatafeedId().equals(ALL) == false && mlMetadata.getDatafeed(request.getDatafeedId()) == null) {
+            if (request.getDatafeedId().equals(ALL) == false
+                    && mlMetadata.getDatafeed(request.getDatafeedId()) == null) {
                 throw ExceptionsHelper.missingDatafeedException(request.getDatafeedId());
             }
 
-            for (DatafeedConfig datafeedConfig : mlMetadata.getDatafeeds().values()) {
+            List<String> expandedDatafeedsIds = request.getDatafeedId().equals(ALL) ?
-                if (request.getDatafeedId().equals(ALL) || datafeedConfig.getId().equals(request.getDatafeedId())) {
+                    mlMetadata.getDatafeeds().values().stream()
-                    PersistentTask<?> task = MlMetadata.getDatafeedTask(request.getDatafeedId(), tasksInProgress);
+                            .map(d -> d.getId()).collect(Collectors.toList())
-                    DatafeedState datafeedState = MlMetadata.getDatafeedState(request.getDatafeedId(), tasksInProgress);
+                    : Collections.singletonList(request.getDatafeedId());
+
+            PersistentTasks tasksInProgress = state.getMetaData().custom(PersistentTasks.TYPE);
+            List<DatafeedStats> results = expandedDatafeedsIds.stream()
+                    .map(datafeedId -> getDatafeedStats(datafeedId, state, tasksInProgress))
+                    .collect(Collectors.toList());
+            QueryPage<DatafeedStats> statsPage = new QueryPage<>(results, results.size(),
+                    DatafeedConfig.RESULTS_FIELD);
+            listener.onResponse(new Response(statsPage));
+        }
+
+        private static DatafeedStats getDatafeedStats(String datafeedId, ClusterState state,
+                                                      PersistentTasks tasks) {
+            PersistentTask<?> task = MlMetadata.getDatafeedTask(datafeedId, tasks);
+            DatafeedState datafeedState = MlMetadata.getDatafeedState(datafeedId, tasks);
             DiscoveryNode node = null;
             String explanation = null;
             if (task != null) {
                 node = state.nodes().get(task.getExecutorNode());
                 explanation = task.getAssignment().getExplanation();
             }
-                    results.put(datafeedConfig.getId(), new DatafeedStats(datafeedConfig.getId(), datafeedState, node, explanation));
+            return new DatafeedStats(datafeedId, datafeedState, node, explanation);
-                }
-            }
-            QueryPage<DatafeedStats> statsPage = new QueryPage<>(new ArrayList<>(results.values()), results.size(),
-                    DatafeedConfig.RESULTS_FIELD);
-            listener.onResponse(new Response(statsPage));
         }
 
         @Override

plugin/src/test/resources/rest-api-spec/test/ml/get_datafeed_stats.yaml

@@ -98,7 +98,36 @@ setup:
   - match: { datafeeds.0.node.attributes.max_running_jobs: "10"}
 
 ---
-"Test explicit get all datafeed stats":
+"Test implicit get all datafeed stats given started datafeeds":
+
+  - do:
+      xpack.ml.open_job:
+        job_id: job-1
+
+  - do:
+      xpack.ml.start_datafeed:
+        "datafeed_id": "datafeed-1"
+        "start": 0
+
+  - do:
+      xpack.ml.open_job:
+        job_id: job-2
+
+  - do:
+      xpack.ml.start_datafeed:
+        "datafeed_id": "datafeed-2"
+        "start": 0
+
+  - do:
+      xpack.ml.get_datafeed_stats: {}
+  - match: { count: 2 }
+  - match: { datafeeds.0.datafeed_id: "datafeed-1"}
+  - match: { datafeeds.0.state: "started"}
+  - match: { datafeeds.1.datafeed_id: "datafeed-2"}
+  - match: { datafeeds.1.state: "started"}
+
+---
+"Test explicit get all datafeed stats given stopped datafeeds":
 
   - do:
       xpack.ml.get_datafeed_stats:
@@ -110,7 +139,7 @@ setup:
   - match: { datafeeds.1.state: "stopped"}
 
 ---
-"Test implicit get all datafeed stats":
+"Test implicit get all datafeed stats given stopped datafeeds":
 
   - do:
       xpack.ml.get_datafeed_stats: {}