Fix IndexShardIT#testDurableFlagHasEffect to only test if operations have been synced

With global checkpoints we also take into account if a global checkpoint must be fsynced.
Yet, with recent addition of inlining global checkpoints into indexing operations from a
test perspective unnecessary fsyncs might be reported if `Translog#syncNeeded` is checked.
Now the test only check if the last write location triggers an fsync instead.

Closes #24600

core/src/test/java/org/elasticsearch/index/shard/IndexShardIT.java

@@ -69,6 +69,7 @@ import org.elasticsearch.test.IndexSettingsModule;
 import org.elasticsearch.test.InternalSettingsPlugin;
 
 import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
@@ -81,6 +82,8 @@ import java.util.concurrent.BrokenBarrierException;
 import java.util.concurrent.CyclicBarrier;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
 
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.emptySet;
@@ -168,33 +171,43 @@ public class IndexShardIT extends ESSingleNodeTestCase {
         IndicesService indicesService = getInstanceFromNode(IndicesService.class);
         IndexService test = indicesService.indexService(resolveIndex("test"));
         IndexShard shard = test.getShardOrNull(0);
-        shard.checkIdle(Long.MIN_VALUE);
+        Translog translog = ShardUtilsTests.getShardEngine(shard).getTranslog();
+        Predicate<Translog> needsSync = (tlog) -> {
+            // we can't use tlog.needsSync() here since it also takes the global checkpoint into account
+            // we explicitly want to check here if our durability checks are taken into account so we only
+            // check if we are synced upto the current write location
+            Translog.Location lastWriteLocation = tlog.getLastWriteLocation();
+            try {
+                // the lastWriteLocaltion has a Integer.MAX_VALUE size so we have to create a new one
+                return tlog.ensureSynced(new Translog.Location(lastWriteLocation.generation, lastWriteLocation.translogLocation, 0));
+            } catch (IOException e) {
+                throw new UncheckedIOException(e);
+            }
+        };
         setDurability(shard, Translog.Durability.REQUEST);
-        assertBusy(() -> assertFalse(ShardUtilsTests.getShardEngine(shard).getTranslog().syncNeeded()));
+        assertFalse(needsSync.test(translog));
         setDurability(shard, Translog.Durability.ASYNC);
         client().prepareIndex("test", "bar", "2").setSource("{}", XContentType.JSON).get();
-        assertTrue(ShardUtilsTests.getShardEngine(shard).getTranslog().syncNeeded());
+        assertTrue(needsSync.test(translog));
         setDurability(shard, Translog.Durability.REQUEST);
         client().prepareDelete("test", "bar", "1").get();
-        shard.checkIdle(Long.MIN_VALUE);
-        assertBusy(() -> assertFalse(ShardUtilsTests.getShardEngine(shard).getTranslog().syncNeeded()));
+        assertFalse(needsSync.test(translog));
 
         setDurability(shard, Translog.Durability.ASYNC);
         client().prepareDelete("test", "bar", "2").get();
-        assertTrue(ShardUtilsTests.getShardEngine(shard).getTranslog().syncNeeded());
+        assertTrue(translog.syncNeeded());
         setDurability(shard, Translog.Durability.REQUEST);
         assertNoFailures(client().prepareBulk()
             .add(client().prepareIndex("test", "bar", "3").setSource("{}", XContentType.JSON))
             .add(client().prepareDelete("test", "bar", "1")).get());
-        shard.checkIdle(Long.MIN_VALUE);
-        assertBusy(() -> assertFalse(ShardUtilsTests.getShardEngine(shard).getTranslog().syncNeeded()));
+        assertFalse(needsSync.test(translog));
 
         setDurability(shard, Translog.Durability.ASYNC);
         assertNoFailures(client().prepareBulk()
             .add(client().prepareIndex("test", "bar", "4").setSource("{}", XContentType.JSON))
             .add(client().prepareDelete("test", "bar", "3")).get());
         setDurability(shard, Translog.Durability.REQUEST);
-        assertTrue(ShardUtilsTests.getShardEngine(shard).getTranslog().syncNeeded());
+        assertTrue(needsSync.test(translog));
     }
 
     private void setDurability(IndexShard shard, Translog.Durability durability) {