Prevent putting V2 index template when overlapping with existing temp…

…late (elastic#54933)

* Prevent putting V2 index template when overlapping with existing template

This change prevents putting V2 index template when it would overlap with existing V2 template
of the same priority

Relates to elastic#53101

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateService.java

@@ -305,7 +305,23 @@ ClusterState addIndexTemplateV2(final ClusterState currentState, final boolean c
             throw new IllegalArgumentException("index template [" + name + "] already exists");
         }
 
-        Map<String, List<String>> overlaps = findConflictingV1Templates(currentState, name, template.indexPatterns());
+        Map<String, List<String>> overlaps = findConflictingV2Templates(currentState, name, template.indexPatterns(), true,
+            template.priority());
+        if (overlaps.size() > 0) {
+            String error = String.format(Locale.ROOT, "index template [%s] has index patterns %s matching patterns from " +
+                    "existing templates [%s] with patterns (%s) that have the same priority [%d], multiple index templates may not " +
+                    "match during index creation, please use a different priority",
+                name,
+                template.indexPatterns(),
+                Strings.collectionToCommaDelimitedString(overlaps.keySet()),
+                overlaps.entrySet().stream()
+                    .map(e -> e.getKey() + " => " + e.getValue())
+                    .collect(Collectors.joining(",")),
+                template.priority());
+            throw new IllegalArgumentException(error);
+        }
+
+        overlaps = findConflictingV1Templates(currentState, name, template.indexPatterns());
         if (overlaps.size() > 0) {
             String warning = String.format(Locale.ROOT, "index template [%s] has index patterns %s matching patterns from " +
                     "existing older templates [%s] with patterns (%s); this template [%s] will take precedence during new index creation",
@@ -385,16 +401,27 @@ static Map<String, List<String>> findConflictingV1Templates(final ClusterState s
      */
     static Map<String, List<String>> findConflictingV2Templates(final ClusterState state, final String candidateName,
                                                                 final List<String> indexPatterns) {
+        return findConflictingV2Templates(state, candidateName, indexPatterns, false, null);
+    }
+
+    /**
+     * Return a map of v2 template names to their index patterns for v2 templates that would overlap
+     * with the given template's index patterns.
+     */
+    static Map<String, List<String>> findConflictingV2Templates(final ClusterState state, final String candidateName,
+                                                                final List<String> indexPatterns, boolean checkPriority, Long priority) {
         Automaton v1automaton = Regex.simpleMatchToAutomaton(indexPatterns.toArray(Strings.EMPTY_ARRAY));
         Map<String, List<String>> overlappingTemplates = new HashMap<>();
         for (Map.Entry<String, IndexTemplateV2> entry : state.metadata().templatesV2().entrySet()) {
             String name = entry.getKey();
             IndexTemplateV2 template = entry.getValue();
             Automaton v2automaton = Regex.simpleMatchToAutomaton(template.indexPatterns().toArray(Strings.EMPTY_ARRAY));
             if (Operations.isEmpty(Operations.intersection(v1automaton, v2automaton)) == false) {
-                logger.debug("old template {} and index template {} would overlap: {} <=> {}",
-                    candidateName, name, indexPatterns, template.indexPatterns());
-                overlappingTemplates.put(name, template.indexPatterns());
+                if (checkPriority == false || Objects.equals(priority, template.priority())) {
+                    logger.debug("old template {} and index template {} would overlap: {} <=> {}",
+                        candidateName, name, indexPatterns, template.indexPatterns());
+                    overlappingTemplates.put(name, template.indexPatterns());
+                }
             }
         }
         return overlappingTemplates;

server/src/test/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateServiceTests.java

@@ -300,12 +300,16 @@ public void testAddIndexTemplateV2() throws Exception {
         assertNotNull(state.metadata().templatesV2().get("foo"));
         assertTemplatesEqual(state.metadata().templatesV2().get("foo"), template);
 
+
+        IndexTemplateV2 newTemplate = randomValueOtherThanMany(t -> Objects.equals(template.priority(), t.priority()),
+            IndexTemplateV2Tests::randomInstance);
+
         final ClusterState throwState = ClusterState.builder(state).build();
         IllegalArgumentException e = expectThrows(IllegalArgumentException.class,
-            () -> metadataIndexTemplateService.addIndexTemplateV2(throwState, true, "foo", template));
+            () -> metadataIndexTemplateService.addIndexTemplateV2(throwState, true, "foo", newTemplate));
         assertThat(e.getMessage(), containsString("index template [foo] already exists"));
 
-        state = metadataIndexTemplateService.addIndexTemplateV2(state, randomBoolean(), "bar", template);
+        state = metadataIndexTemplateService.addIndexTemplateV2(state, randomBoolean(), "bar", newTemplate);
         assertNotNull(state.metadata().templatesV2().get("bar"));
     }
 
@@ -471,6 +475,18 @@ public void testUpdatingV1NonStarWithChangedPatternsTemplateGeneratesError() thr
             "templates (/_index_template) instead"));
     }
 
+    public void testPuttingOverlappingV2Template() throws Exception {
+        IndexTemplateV2 template = new IndexTemplateV2(Arrays.asList("egg*", "baz"), null, null, 1L, null, null);
+        MetadataIndexTemplateService metadataIndexTemplateService = getMetadataIndexTemplateService();
+        ClusterState state = metadataIndexTemplateService.addIndexTemplateV2(ClusterState.EMPTY_STATE, false, "foo", template);
+        IndexTemplateV2 newTemplate = new IndexTemplateV2(Arrays.asList("abc", "baz*"), null, null, 1L, null, null);
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class,
+            () -> metadataIndexTemplateService.addIndexTemplateV2(state, false, "foo2", newTemplate));
+        assertThat(e.getMessage(), equalTo("index template [foo2] has index patterns [abc, baz*] matching patterns from existing " +
+            "templates [foo] with patterns (foo => [egg*, baz]) that have the same priority [1], multiple index templates may not " +
+            "match during index creation, please use a different priority"));
+    }
+
     public void testFindV2Templates() throws Exception {
         final MetadataIndexTemplateService service = getMetadataIndexTemplateService();
         ClusterState state = ClusterState.EMPTY_STATE;