diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -746,6 +746,7 @@
     'DiffusionRepositoryBasicsManagementPanel' => 'applications/diffusion/management/DiffusionRepositoryBasicsManagementPanel.php',
     'DiffusionRepositoryByIDRemarkupRule' => 'applications/diffusion/remarkup/DiffusionRepositoryByIDRemarkupRule.php',
     'DiffusionRepositoryClusterEngine' => 'applications/diffusion/protocol/DiffusionRepositoryClusterEngine.php',
+    'DiffusionRepositoryClusterEngineLogInterface' => 'applications/diffusion/protocol/DiffusionRepositoryClusterEngineLogInterface.php',
     'DiffusionRepositoryClusterManagementPanel' => 'applications/diffusion/management/DiffusionRepositoryClusterManagementPanel.php',
     'DiffusionRepositoryController' => 'applications/diffusion/controller/DiffusionRepositoryController.php',
     'DiffusionRepositoryCreateController' => 'applications/diffusion/controller/DiffusionRepositoryCreateController.php',
@@ -4854,7 +4855,10 @@
     'DiffusionGitReceivePackSSHWorkflow' => 'DiffusionGitSSHWorkflow',
     'DiffusionGitRequest' => 'DiffusionRequest',
     'DiffusionGitResponse' => 'AphrontResponse',
-    'DiffusionGitSSHWorkflow' => 'DiffusionSSHWorkflow',
+    'DiffusionGitSSHWorkflow' => array(
+      'DiffusionSSHWorkflow',
+      'DiffusionRepositoryClusterEngineLogInterface',
+    ),
     'DiffusionGitUploadPackSSHWorkflow' => 'DiffusionGitSSHWorkflow',
     'DiffusionHistoryController' => 'DiffusionController',
     'DiffusionHistoryQueryConduitAPIMethod' => 'DiffusionQueryConduitAPIMethod',
diff --git a/src/applications/diffusion/protocol/DiffusionRepositoryClusterEngine.php b/src/applications/diffusion/protocol/DiffusionRepositoryClusterEngine.php
--- a/src/applications/diffusion/protocol/DiffusionRepositoryClusterEngine.php
+++ b/src/applications/diffusion/protocol/DiffusionRepositoryClusterEngine.php
@@ -13,6 +13,7 @@
   private $viewer;
   private $clusterWriteLock;
   private $clusterWriteVersion;
+  private $logger;
 
 
 /* -(  Configuring Synchronization  )---------------------------------------- */
@@ -36,6 +37,11 @@
     return $this->viewer;
   }
 
+  public function setLog(DiffusionRepositoryClusterEngineLogInterface $log) {
+    $this->logger = $log;
+    return $this;
+  }
+
 
 /* -(  Cluster Synchronization  )-------------------------------------------- */
 
@@ -92,8 +98,36 @@
       $repository_phid,
       $device_phid);
 
-    // TODO: Raise a more useful exception if we fail to grab this lock.
-    $read_lock->lock(phutil_units('2 minutes in seconds'));
+    $lock_wait = phutil_units('2 minutes in seconds');
+
+    $this->logLine(
+      pht(
+        'Waiting up to %s second(s) for a cluster read lock on "%s"...',
+        new PhutilNumber($lock_wait),
+        $device->getName()));
+
+    try {
+      $start = PhabricatorTime::getNow();
+      $read_lock->lock($lock_wait);
+      $waited = (PhabricatorTime::getNow() - $start);
+
+      if ($waited) {
+        $this->logLine(
+          pht(
+            'Acquired read lock after %s second(s).',
+            new PhutilNumber($waited)));
+      } else {
+        $this->logLine(
+          pht(
+            'Acquired read lock immediately.'));
+      }
+    } catch (Exception $ex) {
+      throw new PhutilProxyException(
+        pht(
+          'Failed to acquire read lock after waiting %s second(s). You '.
+          'may be able to retry later.',
+          new PhutilNumber($lock_wait)));
+    }
 
     $versions = PhabricatorRepositoryWorkingCopyVersion::loadVersions(
       $repository_phid);
@@ -126,6 +160,12 @@
           $repository_phid,
           $device_phid,
           $max_version);
+      } else {
+        $this->logLine(
+          pht(
+            'Device "%s" is already a cluster leader and does not need '.
+            'to be synchronized.',
+            $device->getName()));
       }
 
       $result_version = $max_version;
@@ -210,8 +250,35 @@
     $write_lock = PhabricatorRepositoryWorkingCopyVersion::getWriteLock(
       $repository_phid);
 
-    // TODO: Raise a more useful exception if we fail to grab this lock.
-    $write_lock->lock(phutil_units('2 minutes in seconds'));
+    $lock_wait = phutil_units('2 minutes in seconds');
+
+    $this->logLine(
+      pht(
+        'Waiting up to %s second(s) for a cluster write lock...',
+        new PhutilNumber($lock_wait)));
+
+    try {
+      $start = PhabricatorTime::getNow();
+      $write_lock->lock($lock_wait);
+      $waited = (PhabricatorTime::getNow() - $start);
+
+      if ($waited) {
+        $this->logLine(
+          pht(
+            'Acquired write lock after %s second(s).',
+            new PhutilNumber($waited)));
+      } else {
+        $this->logLine(
+          pht(
+            'Acquired write lock immediately.'));
+      }
+    } catch (Exception $ex) {
+      throw new PhutilProxyException(
+        pht(
+          'Failed to acquire write lock after waiting %s second(s). You '.
+          'may be able to retry later.',
+          new PhutilNumber($lock_wait)));
+    }
 
     $versions = PhabricatorRepositoryWorkingCopyVersion::loadVersions(
       $repository_phid);
@@ -393,13 +460,20 @@
    */
   private function synchronizeWorkingCopyFromBinding($binding) {
     $repository = $this->getRepository();
+    $device = AlmanacKeys::getLiveDevice();
+
+    $this->logLine(
+      pht(
+        'Synchronizing this device ("%s") from cluster leader ("%s") before '.
+        'read.',
+        $device->getName(),
+        $binding->getDevice()->getName()));
 
     $fetch_uri = $repository->getClusterRepositoryURIFromBinding($binding);
     $local_path = $repository->getLocalPath();
 
     if ($repository->isGit()) {
       if (!Filesystem::pathExists($local_path)) {
-        $device = AlmanacKeys::getLiveDevice();
         throw new Exception(
           pht(
             'Repository "%s" does not have a working copy on this device '.
@@ -429,7 +503,36 @@
 
     $future->setCWD($local_path);
 
-    $future->resolvex();
+    try {
+      $future->resolvex();
+    } catch (Exception $ex) {
+      $this->logLine(
+        pht(
+          'Synchronization of "%s" from leader "%s" failed: %s',
+          $device->getName(),
+          $binding->getDevice()->getName(),
+          $ex->getMessage()));
+      throw $ex;
+    }
+  }
+
+
+  /**
+   * @task internal
+   */
+  private function logLine($message) {
+    return $this->logText("# {$message}\n");
   }
 
+
+  /**
+   * @task internal
+   */
+  private function logText($message) {
+    $log = $this->logger;
+    if ($log) {
+      $log->writeClusterEngineLogMessage($message);
+    }
+    return $this;
+  }
 }
diff --git a/src/applications/diffusion/protocol/DiffusionRepositoryClusterEngineLogInterface.php b/src/applications/diffusion/protocol/DiffusionRepositoryClusterEngineLogInterface.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/protocol/DiffusionRepositoryClusterEngineLogInterface.php
@@ -0,0 +1,7 @@
+<?php
+
+interface DiffusionRepositoryClusterEngineLogInterface {
+
+  public function writeClusterEngineLogMessage($message);
+
+}
diff --git a/src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php
--- a/src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php
@@ -16,21 +16,37 @@
   protected function executeRepositoryOperations() {
     $repository = $this->getRepository();
     $viewer = $this->getViewer();
+    $device = AlmanacKeys::getLiveDevice();
 
     // This is a write, and must have write access.
     $this->requireWriteAccess();
 
     $cluster_engine = id(new DiffusionRepositoryClusterEngine())
       ->setViewer($viewer)
-      ->setRepository($repository);
+      ->setRepository($repository)
+      ->setLog($this);
 
     if ($this->shouldProxy()) {
       $command = $this->getProxyCommand();
       $did_synchronize = false;
+
+      if ($device) {
+        $this->writeClusterEngineLogMessage(
+          pht(
+            "# Push received by \"%s\", forwarding to cluster host.\n",
+            $device->getName()));
+      }
     } else {
       $command = csprintf('git-receive-pack %s', $repository->getLocalPath());
       $did_synchronize = true;
       $cluster_engine->synchronizeWorkingCopyBeforeWrite();
+
+      if ($device) {
+        $this->writeClusterEngineLogMessage(
+          pht(
+            "# Ready to receive on cluster host \"%s\".\n",
+            $device->getName()));
+      }
     }
 
     $caught = null;
diff --git a/src/applications/diffusion/ssh/DiffusionGitSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionGitSSHWorkflow.php
--- a/src/applications/diffusion/ssh/DiffusionGitSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionGitSSHWorkflow.php
@@ -1,12 +1,18 @@
 <?php
 
-abstract class DiffusionGitSSHWorkflow extends DiffusionSSHWorkflow {
+abstract class DiffusionGitSSHWorkflow
+  extends DiffusionSSHWorkflow
+  implements DiffusionRepositoryClusterEngineLogInterface {
 
   protected function writeError($message) {
     // Git assumes we'll add our own newlines.
     return parent::writeError($message."\n");
   }
 
+  public function writeClusterEngineLogMessage($message) {
+    parent::writeError($message);
+  }
+
   protected function identifyRepository() {
     $args = $this->getArgs();
     $path = head($args->getArg('dir'));
diff --git a/src/applications/diffusion/ssh/DiffusionGitUploadPackSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionGitUploadPackSSHWorkflow.php
--- a/src/applications/diffusion/ssh/DiffusionGitUploadPackSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionGitUploadPackSSHWorkflow.php
@@ -16,18 +16,34 @@
   protected function executeRepositoryOperations() {
     $repository = $this->getRepository();
     $viewer = $this->getUser();
+    $device = AlmanacKeys::getLiveDevice();
 
     $skip_sync = $this->shouldSkipReadSynchronization();
 
     if ($this->shouldProxy()) {
       $command = $this->getProxyCommand();
+
+      if ($device) {
+        $this->writeClusterEngineLogMessage(
+          pht(
+            "# Fetch received by \"%s\", forwarding to cluster host.\n",
+            $device->getName()));
+      }
     } else {
       $command = csprintf('git-upload-pack -- %s', $repository->getLocalPath());
       if (!$skip_sync) {
         $cluster_engine = id(new DiffusionRepositoryClusterEngine())
           ->setViewer($viewer)
           ->setRepository($repository)
+          ->setLog($this)
           ->synchronizeWorkingCopyBeforeRead();
+
+        if ($device) {
+          $this->writeClusterEngineLogMessage(
+            pht(
+              "# Cleared to fetch on cluster host \"%s\".\n",
+              $device->getName()));
+        }
       }
     }
     $command = PhabricatorDaemon::sudoCommandAsDaemonUser($command);