- translate #240 by hand to a patch. Credit to Py Rho for the

original implemenation.

lib/logstash/filters/mutate.rb

@@ -207,12 +207,14 @@ class LogStash::Filters::Mutate < LogStash::Filters::Base
   def replace(event)
     # TODO(sissel): use event.sprintf on the field names?
     @replace.each do |field, newvalue|
+      next unless event.include?(field)
       event[field] = event.sprintf(newvalue)
     end
   end # def replace
 
   def convert(event)
     @convert.each do |field, type|
+      next unless event.include?(field)
       original = event[field]
 
       # calls convert_{string,integer,float} depending on type requested.