list_keys_verbose: preserve ordering with multiple queryworkers

When multiple queryworkers are used in the tracker, it's
possible to receive responses out-of-order.  We need to
hold onto responses while the pipeline is being processed
and only make callbacks when they can be made in the
order the keys were given to us in.

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/mogilefs/mogilefs.rb b/lib/mogilefs/mogilefs.rb
index 5f22152..cfbf082 100644
--- a/lib/mogilefs/mogilefs.rb
+++ b/lib/mogilefs/mogilefs.rb
@@ -250,10 +250,17 @@ class MogileFS::MogileFS < MogileFS::Client
 
   def list_keys_verbose(keys, block) # :nodoc:
     # emulate the MogileFS::Mysql interface, slowly...
+    ordered = keys.dup
+    ready = {}
     on_file_info = lambda do |info|
       Hash === info or raise info
       file_info_cleanup(info)
-      block.call(info["key"], info["length"], info["devcount"])
+
+      # deal with trackers with multiple queryworkers responding out-of-order
+      ready[info["key"]] = info
+      while info = ready.delete(ordered[0])
+        block.call(ordered.shift, info["length"], info["devcount"])
+      end
     end
     opts = { :domain => @domain }
     keys.each do |key|