Plugin Helper: Record Accessor

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The record_accessor plugin helper provides unified access to the event record. It uses jsonpath like syntax for the target field. With this helper, you can easily access/delete a nested field in the plugin.
Here is an example:
require 'fluent/plugin/filter'
​
module Fluent::Plugin
  class ExampleFilter < Filter
    Fluent::Plugin.register_filter('example', self)
​
    # 1. Load record_accessor helper
    helpers :record_accessor
​
    def configure(conf)
      super
​
      # 2. Call `record_accessor_create` to create object
      @accessor = record_accessor_create('$.user.name')
    end
​
    # Omit `super`, `shutdown` and other plugin APIs
​
    def filter(tag, time, record)
      # 3. Call `call` method to get value
      value = @accessor.call(record) # With `$.user.name`, access to record["user"]["name"]
      # ...
    end
  end
end
Syntax
dot notation: $. is the starting parameter. Chain fields with dots ..
For example:
$.event.level for record["event"]["level"]
$.key1[0].key2 for record["key1"][0]["key2"]
bracket notation: $[ starting parameter. Chain fields with [].
Useful for special characters, ., whitespace, etc.
$['dot.key'][0]['space key'] for record["dot.key"][0]["space key"]
If you set non $. or $[ starting value, e.g. key log, it is the same as record["log"]. So, using record_accessor does not break the existing plugin behavior.
Methods
record_accessor_create(param)
This method returns the accessor object of the event record.
The param is a String.
See the "Syntax" section for more details.
record_accessor_create("log")
record_accessor_create("$.key1.key2")
record_accessor_create("$['key1'][0]['key2']")
After creating an object, call call/delete/set method with the record object.
accessor.call(record)       # get record field
accessor.delete(record)     # delete record field
accessor.set(record, value) # set new value to record field
NOTE: set method is supported since v1.10.3
Plugins using record_accessor
​filter_grep​
​filter_parser​
​filter_record_transformer​
If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.

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Syntax

Methods

record_accessor_create(param)

Plugins using record_accessor

Syntax

Methods

`record_accessor_create(param)`

Plugins using `record_accessor`