Fix testGetSnapshotsMultipleRepos (#43993)

The order tested in the equals check in the un-muted test needs exact timestamps. Otherwise two subsequent snapshots might have the same timestamps and hence will get ordered differently than the list of snapshot names that was built as the snapshots were created => Fixed by having exact timestamps in this test.

Author: original-brownbear

server/src/test/java/org/elasticsearch/snapshots/SharedClusterSnapshotRestoreIT.java

@@ -157,6 +157,13 @@ protected Collection<Class<? extends Plugin>> nodePlugins() {
             MockRepository.Plugin.class);
     }
 
+    @Override
+    protected Settings nodeSettings(int nodeOrdinal) {
+        return Settings.builder().put(super.nodeSettings(nodeOrdinal))
+            .put(ThreadPool.ESTIMATED_TIME_INTERVAL_SETTING.getKey(), 0) // We have tests that check by-timestamp order
+            .build();
+    }
+
     private Settings randomRepoSettings() {
         Settings.Builder repoSettings = Settings.builder();
         repoSettings.put("location", randomRepoPath());
@@ -1340,8 +1347,7 @@ public void testGetSnapshotsNoRepos() {
         assertTrue(getSnapshotsResponse.getSuccessfulResponses().isEmpty());
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/pull/43993")
-    public void testGetSnapshotsMultipleRepos() {
+    public void testGetSnapshotsMultipleRepos() throws Exception {
         final Client client = client();
 
         List<String> snapshotList = new ArrayList<>();
@@ -1370,6 +1376,11 @@ public void testGetSnapshotsMultipleRepos() {
             for (int snapshotIndex = 0; snapshotIndex < randomIntBetween(2, 5); snapshotIndex++) {
                 final String snapshotName = randomAlphaOfLength(10).toLowerCase(Locale.ROOT);
                 snapshotList.add(snapshotName);
+                // Wait for at least 1ms to ensure that snapshots can be ordered by timestamp deterministically
+                for (final ThreadPool threadPool : internalCluster().getInstances(ThreadPool.class)) {
+                    final long startMillis = threadPool.absoluteTimeInMillis();
+                    assertBusy(() -> assertThat(threadPool.absoluteTimeInMillis(), greaterThan(startMillis)));
+                }
                 logger.info("--> create snapshot with index {} and name {} in repository {}", snapshotIndex, snapshotName, repoName);
                 CreateSnapshotResponse createSnapshotResponse = client.admin()
                         .cluster()