avoid two instances of EarliestAvailableBlockSlot and minor improvements (#9906)

Author: tbenr

services/beaconchain/src/main/java/tech/pegasys/teku/services/beaconchain/BeaconChainController.java

@@ -327,6 +327,7 @@ public class BeaconChainController extends Service implements BeaconChainControl
   protected volatile AttestationManager attestationManager;
   protected volatile SignatureVerificationService signatureVerificationService;
   protected volatile CombinedChainDataClient combinedChainDataClient;
+  protected volatile EarliestAvailableBlockSlot earliestAvailableBlockSlot;
   protected volatile Eth1DataCache eth1DataCache;
   protected volatile SlotProcessor slotProcessor;
   protected volatile OperationPool<AttesterSlashing> attesterSlashingPool;
@@ -1182,7 +1183,7 @@ private boolean getLivenessTrackingEnabled(final BeaconChainConfiguration beacon
 
   protected void initCombinedChainDataClient() {
     LOG.debug("BeaconChainController.initCombinedChainDataClient()");
-    final EarliestAvailableBlockSlot earliestAvailableBlockSlot =
+    earliestAvailableBlockSlot =
         new EarliestAvailableBlockSlot(
             storageQueryChannel,
             timeProvider,
@@ -1585,10 +1586,7 @@ protected void initP2PNetwork() {
                   recentChainData,
                   throttlingStorageQueryChannel,
                   spec,
-                  new EarliestAvailableBlockSlot(
-                      throttlingStorageQueryChannel,
-                      timeProvider,
-                      beaconConfig.storeConfig().getEarliestAvailableBlockSlotFrequency())));
+                  earliestAvailableBlockSlot));
     }
 
     this.p2pNetwork =

storage/src/main/java/tech/pegasys/teku/storage/client/EarliestAvailableBlockSlot.java

@@ -28,9 +28,8 @@ public class EarliestAvailableBlockSlot {
 
   private final int earliestAvailableBlockSlotFrequency;
 
-  private UInt64 queryTime = UInt64.ZERO;
-
-  private SafeFuture<Optional<UInt64>> earliestAvailableBlockSlotFuture =
+  private volatile UInt64 queryTime = UInt64.ZERO;
+  private volatile SafeFuture<Optional<UInt64>> earliestAvailableBlockSlotFuture =
       SafeFuture.completedFuture(Optional.empty());
 
   public EarliestAvailableBlockSlot(
@@ -64,10 +63,7 @@ private synchronized SafeFuture<Optional<UInt64>> actuallyGetEarliestBlockSlot()
     } else {
       return earliestAvailableBlockSlotFuture;
     }
-    if (!earliestAvailableBlockSlotFuture.isDone()) {
-      // if the current query is not done, we should just return the same future
-      return earliestAvailableBlockSlotFuture;
-    }
+
     LOG.trace("Fetching earliestBlockSlot...");
     earliestAvailableBlockSlotFuture = historicalChainData.getEarliestAvailableBlockSlot();
     return earliestAvailableBlockSlotFuture;