[Monitoring] Stop Accepting .monitoring-data-N index requests via REST (elastic/x-pack-elasticsearch#1318)

Now that the Monitoring UI no longer checks the `.monitoring-data-2` index
for Kibana, Logstash, or Beats data, we can stop accepting the duplicated
data in that index (the _exact_ same documents are also indexed into the
time-based index for each product).

This ignores rather than rejects requests that contain such documents to
allow older clients to communicate with a 5.5+ monitoring cluster.

Original commit: elastic/x-pack-elasticsearch@def472cf2e

plugin/src/main/java/org/elasticsearch/xpack/monitoring/action/MonitoringBulkRequest.java

@@ -94,13 +94,19 @@ public class MonitoringBulkRequest extends ActionRequest {
 
         for (DocWriteRequest request : bulkRequest.requests()) {
             if (request instanceof IndexRequest) {
-                IndexRequest indexRequest = (IndexRequest) request;
+                final IndexRequest indexRequest = (IndexRequest) request;
+
+                // we no longer accept non-timestamped indexes from Kibana, LS, or Beats because we do not use the data
+                // and it was duplicated anyway; by simply dropping it, we allow BWC for older clients that still send it
+                if (MonitoringIndex.from(indexRequest.index()) != MonitoringIndex.TIMESTAMPED) {
+                    continue;
+                }
 
                 // builds a new monitoring document based on the index request
                 MonitoringBulkDoc doc =
                         new MonitoringBulkDoc(defaultMonitoringId,
                                               defaultMonitoringApiVersion,
-                                              MonitoringIndex.from(indexRequest.index()),
+                                              MonitoringIndex.TIMESTAMPED,
                                               indexRequest.type(),
                                               indexRequest.id(),
                                               indexRequest.source(),

plugin/src/test/java/org/elasticsearch/xpack/monitoring/action/MonitoringBulkRequestTests.java

@@ -114,6 +114,7 @@ public class MonitoringBulkRequestTests extends ESTestCase {
         final MonitoringIndex[] indices = new MonitoringIndex[nbDocs];
         final String[] types = new String[nbDocs];
         final XContentType xContentType = XContentType.JSON;
+        int dataCount = 0;
         int i;
 
         try (BytesStreamOutput content = new BytesStreamOutput()) {
@@ -123,8 +124,13 @@ public class MonitoringBulkRequestTests extends ESTestCase {
                     if (rarely()) {
                         indices[i] = MonitoringIndex.DATA;
                         builder.field("_index", "_data");
+                        dataCount++;
                     } else {
                         indices[i] = MonitoringIndex.TIMESTAMPED;
+
+                        if (rarely()) {
+                            builder.field("_index", "");
+                        }
                     }
                     if (randomBoolean()) {
                         types[i] = randomAlphaOfLength(5);
@@ -143,17 +149,20 @@ public class MonitoringBulkRequestTests extends ESTestCase {
 
             MonitoringBulkRequest request = new MonitoringBulkRequest();
             request.add(content.bytes(), defaultMonitoringId, defaultMonitoringVersion, defaultType, xContentType);
-            assertThat(request.getDocs(), hasSize(nbDocs));
+            assertThat(request.getDocs(), hasSize(nbDocs - dataCount));
 
             i = 0;
 
-            for (MonitoringBulkDoc doc : request.getDocs()) {
-                String expectedType = types[i] != null ? types[i] : defaultType;
+            for (final MonitoringBulkDoc doc : request.getDocs()) {
+                // we actively ignore IndexRequests for the _data index; this provides BWC to older versions
+                if (indices[i] != MonitoringIndex.DATA) {
+                    final String expectedType = types[i] != null ? types[i] : defaultType;
 
-                assertThat(doc.getMonitoringId(), equalTo(defaultMonitoringId));
-                assertThat(doc.getMonitoringVersion(), equalTo(defaultMonitoringVersion));
-                assertThat(doc.getIndex(), sameInstance(indices[i]));
-                assertThat(doc.getType(), equalTo(expectedType));
+                    assertThat(doc.getMonitoringId(), equalTo(defaultMonitoringId));
+                    assertThat(doc.getMonitoringVersion(), equalTo(defaultMonitoringVersion));
+                    assertThat(doc.getIndex(), sameInstance(MonitoringIndex.TIMESTAMPED));
+                    assertThat(doc.getType(), equalTo(expectedType));
+                }
 
                 ++i;
             }

plugin/src/test/resources/rest-api-spec/test/monitoring/bulk/10_basic.yaml

@@ -71,12 +71,13 @@
 
   - match: { hits.total: 1 }
 
+  # We actively ignore indexing requests made to .monitoring-data-N starting with 5.5
   - do:
       search:
         index: .monitoring-data-*
         type:  kibana
 
-  - match: { hits.total: 1 }
+  - match: { hits.total: 0 }
 
   # Missing a system_id causes it to fail
   - do:

plugin/src/test/resources/rest-api-spec/test/monitoring/bulk/20_privileges.yaml

@@ -107,11 +107,12 @@ teardown:
         type:  logstash_metric
   - match: { hits.total: 1 }
 
+  # We actively ignore indexing requests made to .monitoring-data-N starting with 5.5
   - do:
       search:
         index: .monitoring-data-*
         type:  logstash_info
-  - match: { hits.total: 1 }
+  - match: { hits.total: 0 }
 
   - do:
       catch: forbidden