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translate.rb
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translate.rb
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# encoding: utf-8
require "logstash/filters/base"
require "logstash/namespace"
# A general search and replace tool which uses a configured hash
# and/or a YAML file to determine replacement values.
#
# The dictionary entries can be specified in one of two ways: First,
# the "dictionary" configuration item may contain a hash representing
# the mapping. Second, an external YAML file (readable by logstash) may be specified
# in the "dictionary_path" configuration item. These two methods may not be used
# in conjunction; it will produce an error.
#
# Operationally, if the event field specified in the "field" configuration
# matches the EXACT contents of a dictionary entry key (or matches a regex if
# "regex" configuration item has been enabled), the field's value will be substituted
# with the matched key's value from the dictionary.
#
# By default, the translate filter will replace the contents of the
# maching event field (in-place). However, by using the "destination"
# configuration item, you may also specify a target event field to
# populate with the new translated value.
#
# Alternatively, for simple string search and replacements for just a few values
# you might consider using the gsub function of the mutate filter.
class LogStash::Filters::Translate < LogStash::Filters::Base
config_name "translate"
milestone 1
# The name of the logstash event field containing the value to be compared for a
# match by the translate filter (e.g. "message", "host", "response_code").
#
# If this field is an array, only the first value will be used.
config :field, :validate => :string, :required => true
# If the destination (or target) field already exists, this configuration item specifies
# whether the filter should skip translation (default) or overwrite the target field
# value with the new translation value.
config :override, :validate => :boolean, :default => false
# The dictionary to use for translation, when specified in the logstash filter
# configuration item (i.e. do not use the @dictionary_path YAML file)
# Example:
#
# filter {
# %PLUGIN% {
# dictionary => [ "100", "Continue",
# "101", "Switching Protocols",
# "merci", "thank you",
# "old version", "new version" ]
# }
# }
# NOTE: it is an error to specify both dictionary and dictionary_path
config :dictionary, :validate => :hash, :default => {}
# The full path of the external YAML dictionary file. The format of the table
# should be a standard YAML file. Make sure you specify any integer-based keys
# in quotes. The YAML file should look something like this:
#
# "100": Continue
# "101": Switching Protocols
# merci: gracias
# old version: new version
#
# NOTE: it is an error to specify both dictionary and dictionary_path
config :dictionary_path, :validate => :path
# When using a dictionary file, this setting will indicate how frequently
# (in seconds) logstash will check the YAML file for updates.
config :refresh_interval, :validate => :number, :default => 300
# The destination field you wish to populate with the translated code. The default
# is a field named "translation". Set this to the same value as source if you want
# to do a substitution, in this case filter will allways succeed. This will clobber
# the old value of the source field!
config :destination, :validate => :string, :default => "translation"
# When `exact => true`, the translate filter will populate the destination field
# with the exact contents of the dictionary value. When `exact => false`, the
# filter will populate the destination field with the result of any existing
# destination field's data, with the translated value substituted in-place.
#
# For example, consider this simple translation.yml, configured to check the `data` field:
# foo: bar
#
# If logstash receives an event with the `data` field set to "foo", and `exact => true`,
# the destination field will be populated with the string "bar".
# If `exact => false`, and logstash receives the same event, the destination field
# will be also set to "bar". However, if logstash receives an event with the `data` field
# set to "foofing", the destination field will be set to "barfing".
#
# Set both `exact => true` AND `regex => `true` if you would like to match using dictionary
# keys as regular expressions. A large dictionary could be expensive to match in this case.
config :exact, :validate => :boolean, :default => true
# If you'd like to treat dictionary keys as regular expressions, set `exact => true`.
# Note: this is activated only when `exact => true`.
config :regex, :validate => :boolean, :default => false
# In case no translation occurs in the event (no matches), this will add a default
# translation string, which will always populate "field", if the match failed.
#
# For example, if we have configured `fallback => "no match"`, using this dictionary:
#
# foo: bar
#
# Then, if logstash received an event with the field `foo` set to "bar", the destination
# field would be set to "bar". However, if logstash received an event with `foo` set to "nope",
# then the destination field would still be populated, but with the value of "no match".
config :fallback, :validate => :string
public
def register
if @dictionary_path
@next_refresh = Time.now + @refresh_interval
registering = true
load_yaml(registering)
end
@logger.debug? and @logger.debug("#{self.class.name}: Dictionary - ", :dictionary => @dictionary)
if @exact
@logger.debug? and @logger.debug("#{self.class.name}: Dictionary translation method - Exact")
else
@logger.debug? and @logger.debug("#{self.class.name}: Dictionary translation method - Fuzzy")
end
end # def register
public
def load_yaml(registering=false)
if !File.exists?(@dictionary_path)
@logger.warn("dictionary file read failure, continuing with old dictionary", :path => @dictionary_path)
return
end
begin
@dictionary.merge!(YAML.load_file(@dictionary_path))
rescue Exception => e
if registering
raise "#{self.class.name}: Bad Syntax in dictionary file #{@dictionary_path}"
else
@logger.warn("#{self.class.name}: Bad Syntax in dictionary file, continuing with old dictionary", :dictionary_path => @dictionary_path)
end
end
end
public
def filter(event)
return unless filter?(event)
if @dictionary_path
if @next_refresh < Time.now
load_yaml
@next_refresh = Time.now + @refresh_interval
@logger.info("refreshing dictionary file")
end
end
return unless event.include?(@field) # Skip translation in case event does not have @event field.
return if event.include?(@destination) and not @override # Skip translation in case @destination field already exists and @override is disabled.
begin
#If source field is array use first value and make sure source value is string
source = event[@field].is_a?(Array) ? event[@field].first.to_s : event[@field].to_s
matched = false
if @exact
if @regex
key = @dictionary.keys.detect{|k| source.match(Regexp.new(k))}
if key
event[@destination] = @dictionary[key]
matched = true
end
elsif @dictionary.include?(source)
event[@destination] = @dictionary[source]
matched = true
end
else
translation = source.gsub(Regexp.union(@dictionary.keys), @dictionary)
if source != translation
event[@destination] = translation
matched = true
end
end
if not matched and @fallback
event[@destination] = @fallback
matched = true
end
filter_matched(event) if matched or @field == @destination
rescue Exception => e
@logger.error("Something went wrong when attempting to translate from dictionary", :exception => e, :field => @field, :event => event)
end
end # def filter
end # class LogStash::Filters::Translate