Class: Fluent::Plugin::SystemdEntryMutator

Inherits:
Object
  • Object
show all
Defined in:
lib/fluent/plugin/systemd/entry_mutator.rb

Overview

A simple stand-alone configurable mutator for systemd journal entries.

Note regarding field mapping: The input field_map option is meant to have a structure that is intuative or logical for humans when declaring a field map. 

"<source_field1>" => "<new_field1>",
"<source_field2>" => ["<new_field1>", "<new_field2>"]

Internally the inverse of the human-friendly field_map is computed (and cached) upon object creation and used as a “mapped model” 

"<new_field1>" => ["<source_field1>", "<source_field2>"],
"<new_field2>" => ["<source_field2>"]

Defined Under Namespace

Classes: Options

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(**options) ⇒ SystemdEntryMutator

Constructor keyword options (all other kwargs are ignored): field_map - hash describing the desired field mapping in the form:

{"<source_field>" => "<new_field>", ...}
where `new_field` is a string or array of strings

field_map_strict - boolean if true will only include new fields

defined in `field_map`

fields_strip_underscores - boolean if true will strip all leading

underscores from non-mapped fields

fields_lowercase - boolean if true lowercase all non-mapped fields

raises Fluent::ConfigError for invalid options



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# File 'lib/fluent/plugin/systemd/entry_mutator.rb', line 45

def initialize(**options)
  @opts = options_from_hash(options)
  validate_options(@opts)
  @map = invert_field_map(@opts.field_map)
  @map_src_fields = @opts.field_map.keys
  @no_transform = @opts == self.class.default_opts
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(sym, *args) ⇒ Object

Expose config state as read-only instance properties of the mutator.



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# File 'lib/fluent/plugin/systemd/entry_mutator.rb', line 54

def method_missing(sym, *args)
  return @opts[sym] if @opts.members.include?(sym)
  super
end

Class Method Details

.default_opts ⇒ Object 



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# File 'lib/fluent/plugin/systemd/entry_mutator.rb', line 30

def self.default_opts
  Options.new({}, false, false, false)
end

Instance Method Details

#format_fields(entry, mapped = nil) ⇒ Object

Run field formatting (mutations applied to all non-mapped fields) against a single journal entry. Returns the mutated entry hash. entry - hash or Systemd::Journal:Entry mapped - Optional hash that represents a previously mapped entry to

which the formatted fields will be added



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# File 'lib/fluent/plugin/systemd/entry_mutator.rb', line 86

def format_fields(entry, mapped = nil)
  mapped ||= {}
  entry.each do |fld, val|
    # don't mess with explicitly mapped fields
    next if @map_src_fields.include?(fld)
    fld = fld.gsub(/\A_+/, "") if @opts.fields_strip_underscores
    fld = fld.downcase if @opts.fields_lowercase
    # account for mapping (appending) to an existing systemd field
    mapped[fld] = mapped.key?(fld) ? [val, mapped[fld]].join(" ") : val
  end
  mapped
end

#map_fields(entry) ⇒ Object

Run field mapping against a single journal entry. Returns the mutated entry hash. entry - hash or Systemd::Journal:Entry



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# File 'lib/fluent/plugin/systemd/entry_mutator.rb', line 71

def map_fields(entry)
  mapped = {}
  @map.each do |cstm, sysds|
    vals = sysds.collect { |fld| entry[fld] }.compact
    next if vals.empty? # systemd field does not exist in source entry
    mapped[cstm] = vals.length == 1 ? vals[0] : vals.join(" ")
  end
  mapped
end

#run(entry) ⇒ Object

The main run method that performs all configured mutations, if any, against a single journal entry. Returns the mutated entry hash. entry - hash or Systemd::Journal:Entry



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# File 'lib/fluent/plugin/systemd/entry_mutator.rb', line 62

def run(entry)
  return entry.to_h if @no_transform
  return map_fields(entry) if @opts.field_map_strict
  format_fields(entry, map_fields(entry))
end