       # Create a job to make a thumbnail for each newly uploaded image
       addedFileJob = (file) ->
          # Don't make new jobs for files tha already have them in process...
-         # findAndModify is atomic, so only one server will succeed and go on to create a job
+         # findAndModify is atomic, so in a multi-server environment,
+         # only one server can succeed and go on to create a job
          myData.rawCollection().findAndModify(
             { _id: new MongoInternals.NpmModule.ObjectID(file._id.toHexString()), 'metadata._Job': {$exists: false}},
             [],

               if err
                  return console.error "Error locking file document in job creation: ", err
               if doc  # This is null if update above didn't succeed
                  console.log "Successfully modified raw collection"
                  outputFileId = myData.insert
                     filename: "tn_#{file.filename}.png"
                     contentType: 'image/png'

                     myData.update({ _id: outputFileId }, { $set: { 'metadata._Job': jobId, 'metadata.thumbOf': file._id }})
                  else
                     console.error "Error saving new job for file #{file._id}"
         )

      # If a removed file has an associated cancellable job, cancel it.
