Move starting world state download process inside WorldDownloadState (#1104)

Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/worldstate/WorldDownloadState.java

@@ -13,6 +13,7 @@
 package tech.pegasys.pantheon.ethereum.eth.sync.worldstate;
 
 import tech.pegasys.pantheon.ethereum.core.BlockHeader;
+import tech.pegasys.pantheon.ethereum.eth.manager.EthScheduler;
 import tech.pegasys.pantheon.ethereum.eth.manager.task.EthTask;
 import tech.pegasys.pantheon.ethereum.worldstate.WorldStateStorage;
 import tech.pegasys.pantheon.ethereum.worldstate.WorldStateStorage.Updater;
@@ -200,4 +201,23 @@ class WorldDownloadState {
   public synchronized void notifyTaskAvailable() {
     notifyAll();
   }
+
+  public CompletableFuture<Void> startDownload(
+      final WorldStateDownloadProcess worldStateDownloadProcess, final EthScheduler ethScheduler) {
+    this.worldStateDownloadProcess = worldStateDownloadProcess;
+    final CompletableFuture<Void> processFuture = worldStateDownloadProcess.start(ethScheduler);
+
+    processFuture.whenComplete(
+        (result, error) -> {
+          if (error != null
+              && !(ExceptionUtils.rootCause(error) instanceof CancellationException)) {
+            // The pipeline is only ever cancelled by us or shutdown closing the EthScheduler
+            // In either case we don't want to consider the download failed as we either already
+            // dealing with it or it's just a normal shutdown. Hence, don't propagate
+            // CancellationException
+            internalFuture.completeExceptionally(error);
+          }
+        });
+    return downloadFuture;
+  }
 }

ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/worldstate/WorldStateDownloader.java

@@ -19,9 +19,7 @@ import tech.pegasys.pantheon.ethereum.worldstate.WorldStateStorage;
 import tech.pegasys.pantheon.metrics.MetricCategory;
 import tech.pegasys.pantheon.metrics.MetricsSystem;
 import tech.pegasys.pantheon.services.tasks.CachingTaskCollection;
-import tech.pegasys.pantheon.util.ExceptionUtils;
 
-import java.util.concurrent.CancellationException;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Function;
@@ -130,19 +128,7 @@ public class WorldStateDownloader {
 
       newDownloadState.setWorldStateDownloadProcess(downloadProcess);
 
-      final CompletableFuture<Void> downloadProcessFuture =
-          downloadProcess.start(ethContext.getScheduler());
-      downloadProcessFuture.whenComplete(
-          (result, error) -> {
-            if (error != null
-                && !(ExceptionUtils.rootCause(error) instanceof CancellationException)) {
-              // If the pipeline was cancelled it's because the download state cancelled it
-              // so don't propagate the cancellation or we'll interfere with the clean up it's
-              // doing.
-              newDownloadState.getDownloadFuture().completeExceptionally(error);
-            }
-          });
-      return newDownloadState.getDownloadFuture();
+      return newDownloadState.startDownload(downloadProcess, ethContext.getScheduler());
     }
   }