Configuration Parameter Types

Types of Configuration Parameters

Common Options

  • default: Specifies the default value for a parameter. If omitted, the

    parameter is required. On startup, Fluentd uses the default value instead if

    the parameter is not configured.

# Required parameter: The configuration must have this parameter like 'param1 10'.
config_param :param1, :integer
# Optional parameter: If the configuration doesn't have 'param2', 100 is used.
config_param :param2, :integer, default: 100
  • secret: If true, the parameter will be masked when Fluentd dumps its

    configuration on the standard output on startup.

config_param :secret_param, :string, secret: true
  • deprecated: Specifies the deprecation warning message. If users use this

    parameter in the configuration, they will see the deprecation warning on

    startup.

config_param :old_param, :string, deprecated: "Use new_param instead"
  • obsoleted: Specifies the obsolete error message. If users use this parameter

    in the configuration, Fluentd raises Fluent::ConfigError and stops.

config_param :dead_param, :string, obsoleted: "This parameter doesn't work anymore"
  • alias: Alias for this parameter as a symbol.

  • skip_accessor: If true, skip adding accessor to the plugin. For internal

    use only!

Data Types

:string

Defines a string parameter.

Code Example:

config_param :name, :string, default: "John Doe", alias: :full_name
config_param :password, :string, secret: true
def configure(conf)
super
log.info(name: @name, password: @password)
end

Configuration Example:

name John Titor
passowrd very-secret-password

:regexp

Defines a regexp parameter. Since v1.2.0.

Code Example:

config_param :pattern, :regexp, default: /^key_/
def configure(conf)
super
log.info(pattern: @pattern)
end
def filter(tag, time, record)
new_record = record.select do |k, v|
@pattern.match(k)
end
new_record
end

Configuration Example:

pattern /^name_/
pattern ^name_ # Also support pattern without slashes

:integer

Defines an integer parameter.

Code Example:

config_param :num_children, :integer, default: 1
def start
super
# ...
@num_children.times do |n|
# do something...
end
end

Configuration Example:

num_children 10

:float

Defines a float parameter.

Code Example:

helpers :timer
config_param :interval, :float, default: 0.5
def start
super
# ...
timer_execute(:in_example, @interval) do
# do something periodically
end
end

Configuration Example:

interval 1.5

:size

Defines a size parameter in bytes.

Available suffixes: { k, m, g, t } (ignore case)

Code Example:

config_param :limit, :size
def do_something
raise "overflow!" if @limit < current
# ...
end

Configuration Example:

limit 10 # 10 byte
limit 10k # 10240 byte
limit 10m # 10485760 byte
limit 10g # 10737418240 byte
limit 10t # 10995116277760 byte

Configuration Example:

limit 10m

:time

Defines the length of the time parameter.

Available suffixes: { s, m, h, d } (lower case only).

If omitted, to_f is applied to the value which converts it to seconds.

Code Example:

config_param :interval, :time
def start
timer_execute(:in_example, @interval) do
# do something periodically
end
end

Configuration Example:

interval 0.5 # 0.5 seconds
interval 1s # 1 second
interval 1m # 1 minute = 60 seconds
interval 1h # 1 hour = 3600 seconds
interval 1d # 1 day = 86400 seconds

Configuration Example:

interval 10m

:bool

Defines a Boolean parameter.

Code Example:

config_param :deep_copy, :bool, default: false
def copy(object)
if @deep_copy
# deep copy
else
# shallow copy
end
end

Configuration Example:

deep_copy true

:enum

Defines an enumerated parameter.

Users can choose a value from the list. If a non-listed value is chosen, an error occurs on startup.

  • Available options

    • list: List of available values.

Code Example:

config_param :protocol_type, :enum, list: [:udp, :tcp], default: :udp
def send
case @protocol_type
when :udp
send_udp
when :tcp
send_tcp
end
end

Configuration Example:

protocol_type tcp

:array

Defines an array parameter.

Users can set an array value for a parameter.

  • Available options

    • value_type: Defines the type of the value.

      Available types: { :string, :integer, :float, :size, :bool, :time }

Code Example:

config_param :users, :array, default: [], value_type: :string
def available_user?(user)
@users.include?(user)
end

Configuration Example:

users user1, user2, user3
users ["user1", "user2", "user3"] # written in JSON

This configuration will be converted to:

["user1", "user2", "user3"]

:hash

Defines a hash parameter.

  • Available options

    • symbolize_keys: If true, the keys are symbolized.

    • value_type: Defines the same type for all values.

Code Example:

config_param :key_values, :hash, default: {}, symbolize_keys: true, value_type: :string
def do_something
value1 = @key_values[:key1]
value2 = @key_values[:key2]
# ...
end

Configuration Example:

key_values {"key1": "value1", "key2": "value2"} # written in JSON
key_values key1:value1,key2:value2

This configurations will be converted to:

{ key1: "value1", key2: "value2" }

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.