Adjust AutoFollowIT#testDataStreams_autoFollowAfterDataStreamCreated(…

…) test (#74541)

Backporting #74468 to 7.13 branch.

Adjust ccr data stream test that tests following a backing index after the
data stream has been auto followed.

Avoid that a data stream matches with a builtin template that uses ilm.
The manual rollover that happens in this test, may cause ilm to add
`index.lifecycle.indexing_complete` setting, which causes explicit
follow index api call to fail in this test

Closes #72062

x-pack/plugin/ccr/qa/multi-cluster/src/test/java/org/elasticsearch/xpack/ccr/AutoFollowIT.java

@@ -309,12 +309,21 @@ public void testDataStreams_autoFollowAfterDataStreamCreated() throws Exception
 
         final int initialNumDocs = 16;
         int initialNumberOfSuccessfulFollowedIndices = getNumberOfSuccessfulFollowedIndices();
-        final String dataStreamName = "logs-syslog-prod";
-        final String autoFollowPatternName = getTestName().toLowerCase(Locale.ROOT);
+        // The data stream name shouldn't match with builtin ilm policies to avoid test instabilities.
+        // (the manual rollover that happens in this test, may cause ilm to add `index.lifecycle.indexing_complete` setting,
+        // which causes explicit follow index api call to fail in this test)
+        final String dataStreamName = getTestName().toLowerCase(Locale.ROOT) + "-logs-syslog-prod";
+        // Because the builtin logs template isn't used, a template should be defined here.
+        Request putComposableIndexTemplateRequest = new Request("POST", "/_index_template/" + getTestName().toLowerCase(Locale.ROOT));
+        putComposableIndexTemplateRequest.setJsonEntity("{\"index_patterns\":[\"" + dataStreamName + "*\"],\"data_stream\":{}}");
+        assertOK(client().performRequest(putComposableIndexTemplateRequest));
 
+        final String autoFollowPatternName = getTestName().toLowerCase(Locale.ROOT);
         try {
             // Initialize data stream prior to auto following
             try (RestClient leaderClient = buildLeaderClient()) {
+                assertOK(leaderClient.performRequest(putComposableIndexTemplateRequest));
+
                 for (int i = 0; i < initialNumDocs; i++) {
                     Request indexRequest = new Request("POST", "/" + dataStreamName + "/_doc");
                     indexRequest.addParameter("refresh", "true");
@@ -326,7 +335,7 @@ public void testDataStreams_autoFollowAfterDataStreamCreated() throws Exception
             }
 
             // Create auto follow pattern
-            createAutoFollowPattern(client(), autoFollowPatternName, "logs-syslog-*", "leader_cluster");
+            createAutoFollowPattern(client(), autoFollowPatternName, dataStreamName + "*", "leader_cluster");
 
             // Rollover and ensure only second backing index is replicated:
             try (RestClient leaderClient = buildLeaderClient()) {