[Tests] Make testEngineGCDeletesSetting deterministic

server/src/main/java/org/elasticsearch/threadpool/ThreadPool.java

@@ -550,22 +550,39 @@ static class CachedTimeThread extends Thread {
             this.absoluteMillis = System.currentTimeMillis();
             this.counter = new TimeCounter();
             setDaemon(true);
+            if (interval <= 0) {
+                this.running = false;
+            }
         }
 
         /**
          * Return the current time used for relative calculations. This is
          * {@link System#nanoTime()} truncated to milliseconds.
+         * <p>
+         * If {@link ThreadPool#ESTIMATED_TIME_INTERVAL_SETTING} is set to 0
+         * then the cache is disabled and the method calls {@link System#nanoTime()}
+         * whenever called. Typically used for testing.
          */
         long relativeTimeInMillis() {
-            return relativeMillis;
+            if (running) {
+                return relativeMillis;
+            }
+            return TimeValue.nsecToMSec(System.nanoTime());
         }
 
         /**
          * Return the current epoch time, used to find absolute time. This is
          * a cached version of {@link System#currentTimeMillis()}.
+         * <p>
+         * If {@link ThreadPool#ESTIMATED_TIME_INTERVAL_SETTING} is set to 0
+         * then the cache is disabled and the method calls {@link System#currentTimeMillis()}
+         * whenever called. Typically used for testing.
          */
         long absoluteTimeInMillis() {
-            return absoluteMillis;
+            if (running) {
+                return absoluteMillis;
+            }
+            return System.currentTimeMillis();
         }
 
         @Override

server/src/test/java/org/elasticsearch/indices/settings/UpdateSettingsIT.java

@@ -32,6 +32,7 @@
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.test.ESIntegTestCase;
+import org.elasticsearch.threadpool.ThreadPool;
 
 import java.util.Arrays;
 import java.util.Collection;
@@ -126,6 +127,16 @@ public List<Setting<?>> getSettings() {
         }
     }
 
+    /**
+     * Needed by {@link UpdateSettingsIT#testEngineGCDeletesSetting()}
+     */
+    @Override
+    protected Settings nodeSettings(int nodeOrdinal) {
+        return Settings.builder().put(super.nodeSettings(nodeOrdinal))
+            .put("thread_pool.estimated_time_interval", 0)
+            .build();
+    }
+
     public void testUpdateDependentClusterSettings() {
         IllegalArgumentException iae = expectThrows(IllegalArgumentException.class, () ->
             client().admin().cluster().prepareUpdateSettings().setPersistentSettings(Settings.builder()
@@ -435,23 +446,31 @@ public void testOpenCloseUpdateSettings() throws Exception {
         assertThat(getSettingsResponse.getSetting("test", "index.final"), nullValue());
     }
 
-    public void testEngineGCDeletesSetting() throws InterruptedException {
+    public void testEngineGCDeletesSetting() {
         createIndex("test");
         client().prepareIndex("test", "type", "1").setSource("f", 1).get();
         DeleteResponse response = client().prepareDelete("test", "type", "1").get();
         long seqNo = response.getSeqNo();
         long primaryTerm = response.getPrimaryTerm();
         // delete is still in cache this should work
         client().prepareIndex("test", "type", "1").setSource("f", 2).setIfSeqNo(seqNo).setIfPrimaryTerm(primaryTerm).get();
-        client().admin().indices().prepareUpdateSettings("test").setSettings(Settings.builder().put("index.gc_deletes", 0)).get();
+        assertAcked(client().admin().indices().prepareUpdateSettings("test").setSettings(Settings.builder().put("index.gc_deletes", 0)));
 
         response = client().prepareDelete("test", "type", "1").get();
         seqNo = response.getSeqNo();
-        Thread.sleep(300); // wait for cache time to change TODO: this needs to be solved better. To be discussed.
+
+        // Make sure the time has advanced for InternalEngine#resolveDocVersion()
+        for (ThreadPool tPool : internalCluster().getInstances(ThreadPool.class)) {
+            long time1 = tPool.relativeTimeInMillis();
+            long time2 = tPool.relativeTimeInMillis();
+            while (time1 == time2) {
+                time2 = tPool.relativeTimeInMillis();
+            }
+        }
+
         // delete is should not be in cache
         assertThrows(client().prepareIndex("test", "type", "1").setSource("f", 3).setIfSeqNo(seqNo).setIfPrimaryTerm(primaryTerm),
             VersionConflictEngineException.class);
-
     }
 
     public void testUpdateSettingsWithBlocks() {