At create database wait for synchronous replication to kick in.

js/server/upgrade-database.js

@@ -155,6 +155,33 @@
       return collectionExists(name);
     }
 
+    function waitForSyncRepl(dbName, collName) {
+      console.debug("waitForSyncRepl:", dbName, collName);
+      var cinfo = global.ArangoClusterInfo.getCollectionInfo(dbName, collName);
+      var count = 120;
+      while (--count > 0) {
+        var shards = Object.keys(cinfo.shards);
+        var ccinfo = shards.map(function(s) {
+          return global.ArangoClusterInfo.getCollectionInfoCurrent(dbName,
+                    collName, s).servers;
+        });
+        console.debug("waitForSyncRepl", shards, cinfo.shards, ccinfo);
+        var ok = true;
+        for (var i = 0; i < shards.length; ++i) {
+          if (cinfo.shards[shards[i]].length !== ccinfo[i].length) {
+            ok = false;
+          }
+        }
+        if (ok) {
+          console.debug("waitForSyncRepl: OK");
+          return true;
+        }
+        require("internal").wait(1.0);
+      }
+      console.warn("waitForSyncRepl: BAD");
+      return false;
+    }
+
     ////////////////////////////////////////////////////////////////////////////////
     // adds a task
     ///
@@ -773,6 +800,26 @@
       }
     });
 
+    // waitForSyncReplication
+    addTask({
+      name: "waitSyncReplSettle",
+      description: "wait until synchronous replication has settled",
+
+      system: DATABASE_ALL,
+      cluster: [CLUSTER_COORDINATOR_GLOBAL],
+      database: [DATABASE_INIT],
+
+      task: function() {
+        var dbName = db._name();
+        var colls = db._collections();
+        colls = colls.filter(c => c.name()[0] === "_");
+        colls.forEach(function(c) {
+          waitForSyncRepl(dbName, c.name());
+        });
+        return true;
+      }
+    });
+
     return upgradeDatabase();
   }