compute indexes in child processes

lib/storage/file.js

@@ -1024,16 +1024,17 @@ module.exports.create = function (conf, cb) {
         // make sure the store's directory exists
         Fse.mkdirp(env.root, PERMISSIVE, w(function (err) {
             if (err && err.code !== 'EEXIST') {
-                throw err;
+                throw err; // XXX
             }
         }));
         // make sure the cold storage directory exists
         Fse.mkdirp(env.archiveRoot, PERMISSIVE, w(function (err) {
             if (err && err.code !== 'EEXIST') {
-                throw err;
+                throw err; // XXX
             }
         }));
     }).nThen(function () {
+        // XXX leave a place for an error
         cb({
         // OLDER METHODS
             // write a new message to a log
@@ -1078,6 +1079,12 @@ module.exports.create = function (conf, cb) {
                 });
             },
 
+            getWeakLock: function (channelName, _cb) {
+                var cb = Util.once(Util.mkAsync(_cb));
+                if (!isValidChannelId(channelName)) { return void cb(new Error('EINVAL')); }
+                schedule.unordered(channelName, cb);
+            },
+
         // METHODS for deleting data
             // remove a channel and its associated metadata log if present
             removeChannel: function (channelName, cb) {