Plugin Helper: Storage

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The storage plugin helper manages the plugin's internal states.
Here is an example:
require 'fluent/plugin/input'
​
module Fluent::Plugin
  class ExampleInput < Input
    Fluent::Plugin.register_input('awesome_example', self)
​
    # 1. Load storage helper
    helpers :storage, :thread
​
    DEFAULT_STORAGE_TYPE = 'local'
​
    # Omit `shutdown` and other plugin APIs
​
    def initialize
      super
​
      @storage = nil
    end
​
    def configure(conf)
      super
​
      # 2. Create storage with unique name
      config = conf.elements(name: 'storage').first
      @storage = storage_create(usage: 'awesome_index', conf: config, default_type: DEFAULT_STORAGE_TYPE)
    end
​
    def start
      super
​
      # 3. Call storage plugin helpers get/put methods
      @storage.put(:awesome_index, 0) unless @storage.get(:awesome_index)
      thread_create(:awesome_input_runner, &method(:run))
    end
​
    def run
      while thread_current_running?
        current_time = Time.now.to_i
        break unless (thread_current_running? && Time.now.to_i <= current_time)
        router.emit('awesome', Fluent::Engine.now, generate)
        sleep 0.1
      end
    end
​
    def generate
      # 4. Update storage plugin helper's storing value
      @storage.update(:awesome_index) { |v| v + 1 }
    end
  end
end
The created storage is managed by the plugin helper. No need of storage shutdown code in plugin's shutdown. It shutdowns the created storages automatically.
For more details, see Storage section.
Methods
storage_create(usage: '', type: nil, conf: nil, default_type: nil)
This method executes storage with the given parameters and routine.
usage: unique string value (default: '')
type: storage plugin type (default: nil)
conf: storage plugin configuration (default: nil)
default_conf: storage plugin default configuration (default: nil)
Storage Plugin Helper Instance Types
Instance Type
Attributes
Raw | persistent && persistent_always? || otherwise | Persistent Wrapper | persistent | Synchronized Wrapper | !synchronized? |
Raw
Storage plugins will handle as-is.
Persistent Wrapper
This wrapper makes the handled storage plugin operate values persistently.
Synchronized Wrapper
This wrapper makes handled storage plugin operate values synchronically.
Common Methods
Storage plugin helper encapsulates storage plugin implementation. Normally, the following methods will be called by the owner plugin through this plugin helper:
load
This method loads persistently stored value.
save
This method saves value persistently.
get(key)
key: symbol value.
This method obtains stored value by key.
fetch(key, defval)
key: symbol value.
defval: default value.
This method obtains the stored value by key. If missing, it returns the default value.
put(key, value)
key: symbol value.
value: store value.
This method updates the stored value by key.
delete(key)
key: symbol value.
This method deletes the stored value by key.
update(key, &block)
key: symbol value.
&block: a Proc object.
This method updates the stored value using a Proc object.
Plugins using storage
​in_sample​
​in_windows_eventlog​
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.

Plugin Helper: Socket

Plugin Helper: Thread

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Methods

storage_create(usage: '', type: nil, conf: nil, default_type: nil)

Storage Plugin Helper Instance Types

Common Methods

Plugins using storage

Methods

`storage_create(usage: '', type: nil, conf: nil, default_type: nil)`

Storage Plugin Helper Instance Types

Raw

Persistent Wrapper

Synchronized Wrapper

Common Methods

`load`

`save`

`get(key)`

`fetch(key, defval)`

`put(key, value)`

`delete(key)`

`update(key, &block)`

Plugins using `storage`