class LogStash::Filters::Prune
The prune filter is for removing fields from events based on whitelists or blacklist of field names or their values (names and values can also be regular expressions).
This can e.g. be useful if you have a <<plugins-filters-json,json>> or <<plugins-filters-kv,kv>> filter that creates a number of fields with names that you don't necessarily know the names of beforehand, and you only want to keep a subset of them.
Usage help: To specify a exact field name or value use the regular expression syntax `^some_name_or_value$`. Example usage: Input data `{ “msg”:“hello world”, “msg_short”:“hw” }`
- source,ruby
-
filter {
%PLUGIN% { whitelist_names => [ "msg" ] }
}
Allows both `“msg”` and `“msg_short”` through.
While:
- source,ruby
-
filter {
%PLUGIN% { whitelist_names => ["^msg$"] }
}
Allows only `“msg”` through.
Logstash stores an event's `tags` as a field which is subject to pruning. Remember to `whitelist_names => [ “^tags$” ]` to maintain `tags` after pruning or use `blacklist_values => [ “^tag_name$” ]` to eliminate a specific `tag`.
NOTE: This filter currently only support operations on top-level fields, i.e. whitelisting and blacklisting of subfields based on name or value does not work.
Public Instance Methods
# File lib/logstash/filters/prune.rb, line 107 def filter(event) hash = event.to_hash # We need to collect fields which needs to be remove ,and only in the end # actually remove it since then interpolation mode you can get unexpected # results as fields with dynamic values will not match since the fields to # which they refer have already been removed. fields_to_remove = [] unless @whitelist_names.empty? @whitelist_names_regexp = Regexp.union(@whitelist_names.map {|x| Regexp.new(event.sprintf(x))}) if @interpolate hash.each_key do |field| fields_to_remove << field unless field.match(@whitelist_names_regexp) end end unless @blacklist_names.empty? @blacklist_names_regexp = Regexp.union(@blacklist_names.map {|x| Regexp.new(event.sprintf(x))}) if @interpolate hash.each_key do |field| fields_to_remove << field if field.match(@blacklist_names_regexp) end end @whitelist_values.each do |key, value| if @interpolate key = event.sprintf(key) value = Regexp.new(event.sprintf(value)) end if hash[key] if hash[key].is_a?(Array) subvalues_to_remove = hash[key].find_all{|x| not x.match(value)} unless subvalues_to_remove.empty? fields_to_remove << (subvalues_to_remove.length == hash[key].length ? key : { :key => key, :values => subvalues_to_remove }) end else fields_to_remove << key if not hash[key].match(value) end end end @blacklist_values.each do |key, value| if @interpolate key = event.sprintf(key) value = Regexp.new(event.sprintf(value)) end if hash[key] if hash[key].is_a?(Array) subvalues_to_remove = hash[key].find_all{|x| x.match(value)} unless subvalues_to_remove.empty? fields_to_remove << (subvalues_to_remove.length == hash[key].length ? key : { :key => key, :values => subvalues_to_remove }) end else fields_to_remove << key if hash[key].match(value) end end end fields_to_remove.each do |field| if field.is_a?(Hash) event.set(field[:key], hash[field[:key]] - field[:values]) else hash.delete(field) event.remove(field) end end filter_matched(event) end
# File lib/logstash/filters/prune.rb, line 93 def register unless @interpolate @whitelist_names_regexp = Regexp.union(@whitelist_names.map {|x| Regexp.new(x)}) @blacklist_names_regexp = Regexp.union(@blacklist_names.map {|x| Regexp.new(x)}) @whitelist_values.each do |key, value| @whitelist_values[key] = Regexp.new(value) end @blacklist_values.each do |key, value| @blacklist_values[key] = Regexp.new(value) end end end