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https://github.com/fluent/fluent-logger-ruby

A structured logger for Fluentd (Ruby)
https://github.com/fluent/fluent-logger-ruby

fluentd fluentd-logger ruby

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A structured logger for Fluentd (Ruby)

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# Fluent logger



[![Build Status](https://github.com/fluent/fluent-logger-ruby/actions/workflows/linux.yml/badge.svg?branch=master)](https://github.com/fluent/fluent-logger-ruby/actions/workflows/linux.yml)



A structured event logger



## Installation



Add this line to your application's Gemfile:



```ruby

gem 'fluent-logger'

```



And then execute:



    $ bundle install



Or install it yourself as:



    $ gem install fluent-logger



## Examples



### Simple



```ruby

require 'fluent-logger'



# API: FluentLogger.new(tag_prefix, options)

log = Fluent::Logger::FluentLogger.new(nil, :host => 'localhost', :port => 24224)

unless log.post("myapp.access", {"agent" => "foo"})

  p log.last_error # You can get last error object via last_error method

end



# output: myapp.access {"agent":"foo"}

```



### UNIX socket



```ruby

require 'fluent-logger'



log = Fluent::Logger::FluentLogger.new(nil, :socket_path => "/tmp/fluent.sock")

unless log.post("myapp.access", {"agent" => "foo"})

  # Passed records are stored into logger's internal buffer so don't re-post same event.

  p log.last_error # You can get last error object via last_error method

end



# output: myapp.access {"agent":"foo"}

```



### Tag prefix

```ruby

require 'fluent-logger'



log = Fluent::Logger::FluentLogger.new('myapp', :host => 'localhost', :port => 24224)

log.post("access", {"agent" => "foo"})



# output: myapp.access {"agent":"foo"}

```



### Nonblocking write



```ruby

require 'fluent-logger'



log = Fluent::Logger::FluentLogger.new(nil, :host => 'localhost', :port => 24224, :use_nonblock => true, :wait_writeable => false)

# When wait_writeable is false

begin

  log.post("myapp.access", {"agent" => "foo"})

rescue IO::EAGAINWaitWritable => e

  # wait code for avoding "Resource temporarily unavailable"

  # Passed records are stored into logger's internal buffer so don't re-post same event.

end



# When wait_writeable is true

unless log.post("myapp.access", {"agent" => "foo"})

  # same as other example

end



# output: myapp.access {"agent":"foo"}

```



### TLS setting



```ruby

require 'fluent-logger'



tls_opts = {

  :ca   => '/path/to/cacert.pem',

  :cert => '/path/to/client-cert.pem',

  :key  => '/path/to/client-key.pem',

  :key_passphrase => 'test'

}

log = Fluent::Logger::FluentLogger.new(nil, :host => 'localhost', :port => 24224, :tls_options => tls_opts)

```



`in_forward` config example:



```



  @type forward

  

    version TLS1_2

    ca_path /path/to/cacert.pem

    cert_path /path/to/server-cert.pem

    private_key_path /path/to/server-key.pem

    private_key_passphrase test

    client_cert_auth true

  



```



### Singleton

```ruby

require 'fluent-logger'



Fluent::Logger::FluentLogger.open(nil, :host => 'localhost', :port => 24224)

Fluent::Logger.post("myapp.access", {"agent" => "foo"})



# output: myapp.access {"agent":"foo"}

```



### Logger options



#### host (String)



fluentd instance host



#### port (Integer)



fluentd instance port



#### socket_path (String)



If specified, fluentd uses unix domain socket instead of TCP.



#### nanosecond_precision (Bool)



Use nano second event time instead of epoch. See also "Tips" section.



#### use_nonblock (Bool)



Use nonblocking write(`IO#write_nonblock`) instead of normal write(`IO#write`). If `Logger#post` stuck on your environment, specify `true`.  Default: `false`



#### wait_writeable (Bool)



If `false`, `Logger#post` raises an error when nonblocking write gets `EAGAIN` (i.e. `use_nonblock` must be `true`, otherwise this will have no effect).  Default: `true`



#### buffer_overflow_handler (Proc)



Pass callback for handling buffer overflow with pending data. See "Buffer overflow" section.



#### tls_options (Hash)



Pass TLS related options.



- use_default_ca: Set `true` if you want to use default CA

- ca: CA file path

- cert: Certificate file path

- key: Private key file path

- key_passphrase: Private key passphrase

- version: TLS version. Default is `OpenSSL::SSL::TLS1_2_VERSION`

- ciphers: The list of cipher suites. Default is `ALL:!aNULL:!eNULL:!SSLv2`

- insecure: Set `true` when `in_forward` uses `insecure true`



### Standard ::Logger compatible interface



#### Example1



```ruby

require 'fluent-logger'

f = Fluent::Logger::LevelFluentLogger.new('fluent')



f.info("some application running.")

# output: fluent.info: {"level":"INFO","message":"some application running."}



f.warn("some application running.")

# output: fluent.warn: {"level":"WARN","message":"some application running."}

```



#### Example2(add progname)



```ruby

require 'fluent-logger'

f = Fluent::Logger::LevelFluentLogger.new('fluent')

f.info("some_application") {"some application running."}

# output: fluent.info: {"level":"INFO","message":"some application running.","progname":"some_application"}

```



#### Example3(set log level)



```ruby

require 'fluent-logger'

f = Fluent::Logger::LevelFluentLogger.new('fluent')

f.level = Logger::WARN

f.info("some_application") {"some application running."}

```



Log level is ERROR so no output.



default log level is debug.



#### Example4(customize format for Rails)



```ruby

require 'fluent-logger'

f = Fluent::Logger::LevelFluentLogger.new('fluent')



f.formatter = proc do |severity, datetime, progname, message|

  map = { level: severity }

  map[:message] = message if message

  map[:progname] = progname if progname

  map[:stage] = ENV['RAILS_ENV']

  map[:service_name] = "SomeApp"

  map

end



f.info("some_application"){"some application running."}

# output: fluent.info: {"level":"INFO","message":"some application running.","progname":"some_application","stage":"production","service_name":"SomeApp"}

```



## Loggers



### Fluent

```ruby

Fluent::Logger::FluentLogger.open('tag_prefix', :host => 'localhost', :port => 24224)

```



### Console

```ruby

Fluent::Logger::ConsoleLogger.open(io)

```



### Null

```ruby

Fluent::Logger::NullLogger.open

```



## Tips



### Use nanosecond-precision time



To send events with nanosecond-precision time (Fluent 0.14 and up), specify `nanosecond_precision` to `FluentLogger` constructor.



```ruby

log = Fluent::Logger::FluentLogger.new(nil, :host => 'localhost', :port => 24224, :nanosecond_precision => true)

# Use nanosecond time instead

log.post("myapp.access", {"agent" => "foo"})

log.post_with_time("myapp.access", {"agent" => "foo"}, Time.now) # Need Time object for post_with_time

```



### Buffer overflow



You can inject your own custom proc to handle buffer overflow in the event of connection failure. This will mitigate the loss of data instead of simply throwing data away.



Your proc must accept a single argument, which will be the internal buffer of messages from the logger. A typical use-case for this would be writing to disk or possibly writing to Redis.



##### Example

```ruby

class BufferOverflowHandler

  attr_accessor :buffer



  def flush(messages)

    @buffer ||= []

    MessagePack::Unpacker.new.feed_each(messages) do |msg|

      @buffer << msg

    end

  end

end



handler = Proc.new { |messages| BufferOverflowHandler.new.flush(messages) }



Fluent::Logger::FluentLogger.new(nil,

  :host => 'localhost', :port => 24224,

  :buffer_overflow_handler => handler)

```



## Information



|name|description|

|---|---|

|Web site|http://fluentd.org/ |

|Documents|http://docs.fluentd.org/ |

|Source repository|https://github.com/fluent/fluent-logger-ruby |

|Author|Sadayuki Furuhashi|

|Copyright|(c) 2011 FURUHASHI Sadayuki|

|License|Apache License, Version 2.0|