Kiev

Kiev is a comprehensive logging library aimed at covering a wide range of frameworks and tools from the Ruby ecosystem:

Rails
Sinatra
Rack and other Rack-based frameworks
Sidekiq
Que
Shoryuken
Her and other Faraday-based libraries
HTTParty

The main goal of Kiev is consistent logging across distributed systems, like tracking HTTP requests across various Ruby micro-services. Kiev will generate and propagate request IDs and make it easy for you to identify service calls and branching requests, including background jobs triggered by these requests.

Aside from web requests and background jobs, which are tracked out of the box, Kiev makes it easy to append additional information or introduce custom events.

Kiev produces structured logs in the JSON format, which are ready to be ingested by ElasticSearch or other similar JSON-driven data stores. It eliminates the need for Logstash in a typical ELK stack.

In development mode, Kiev can print human-readable logs - pretty much like the default Rails logger, but including all the additional information that you've provided via Kiev events.

Install

Add the gem to your Gemfile:

gem "kiev"

Don't forget to bundle install.

Configure

Rails

Place your configuration under config/initializers/kiev.rb:

require "kiev"

Kiev.configure do |config|
  config.app = :my_app
  config.development_mode = Rails.env.development?
  config.log_path = Rails.root.join("log", "structured.log") unless Rails.env.development? || $stdout.isatty
end

The middleware stack is included automatically via a Railtie.

Sinatra

Somewhere in your code, ideally before the server configuration, add the following lines:

require "kiev"

Kiev.configure do |config|
  config.app = :my_app
  config.log_path = File.join("log", "structured.log")
end

Within your Sinatra::Base implementation, include the Kiev::Rack module, in order to register the middleware stack:

require "kiev"
require "sinatra/base"

class MyController < Sinatra::Base
  include Kiev::Rack

  use SomeOtherMiddleware

  get "/hello" do
    "world"
  end
end

Rack

Somewhere in your code, ideally before the server configuration, add the following lines:

require "kiev"

Kiev.configure do |config|
  config.app = :my_app
  config.log_path = File.join("log", "structured.log")
end

Within your Rack::Builder implementation, include the Kiev::Rack module, in order to register the middleware stack:

require "kiev"
require "rack"

app = Rack::Builder.new do
  include Kiev::Rack

  use SomeOtherMiddleware

  run labmda { |env| [ 200, {}, [ "hello world" ] ] }
end

run(app)

Hanami

Place your configuration under config/initializers/kiev.rb:

require "kiev"

Kiev.configure do |config|
  config.app = :my_app
  config.development_mode = Hanami.env?(:development)
  config.log_path = File.join("log", "structured.log")
end

Within your MyApp::Application file, include the Kiev::Hanami module, in order to register the middleware stack. The include should be added before configure block.

module MyApp
  class Application < Hanami::Application
    include Kiev::Hanami

    configure do
      # ...
    end
  end
end

Sidekiq

Add the following lines to your initializer code:

Kiev::Sidekiq.enable

Shoryuken

Add the following lines to your initializer code:

Kiev::Shoryuken.enable

The name of the worker class is not logged by default. Configure persistent_log_fields option to include "shoryuken_class" if you want this.

Que

Add the following lines to your initializer code:

require "kiev/que/job"

class MyJob < Kiev::Que::Job
  ...
end

Her

Add the following lines to your initializer code:

Her::API.setup(url: "https://api.example.com") do |c|
  c.use Kiev::HerExt::ClientRequestId
  # other middleware
end

Loading only the required parts

You can load only parts of the gem, if you don't want to use all features:

require "kiev/her_ext/client_request_id"

Logging

Requests

For web requests the Kiev middleware will log the following information by default:

{
  "application":"my_app",
  "event":"request_finished",
  "level":"INFO",
  "timestamp":"2017-01-27T16:11:44.123Z",
  "host":"localhost",
  "verb":"GET",
  "path":"/",
  "params":"{\"hello\":\"world\",\"password\":\"[FILTERED]\"}",
  "ip":"127.0.0.1",
  "request_id":"UUID",
  "request_depth":0,
  "route":"RootController#index",
  "user_agent":"curl/7.50.1",
  "status":200,
  "request_duration":62.3773,
  "body":"See #log_response_body_condition",
  "error_message": "...",
  "error_class": "...",
  "error_backtrace": "...",
  "tree_path": "ACE",
  "tree_leaf": true
}

params attribute will store both query parameters and request body fields (as long as they are parseable). Sensitive fields will be filtered out - see the #filtered_params option.
request_id is the correlation ID and will be the same across all requests within a chain of requests. It's represented as a UUID (version 4).
request_depth represents the position of the current request within a chain of requests. It starts with 0.
route attribute will be set to either the Rails route (RootController#index) or Sinatra route (/) or the path, depending on the context.
request_duration is measured in miliseconds.
body attribute coresponds to the response body and will be logged depending on the #log_response_body_condition option.
tree_path attribute can be used to follow the branching of requests within a chain of requests. It's a lexicographically sortable string.
tree_leaf points out that this request is a leaf in the request chain tree structure.

Background jobs

For background jobs, Kiev will log the following information by default:

{
  "application":"my_app",
  "event":"job_finished",
  "level":"INFO",
  "timestamp":"2017-01-27T16:11:44.123Z",
  "job_name":"name",
  "params": "...",
  "jid":123,
  "request_id":"UUID",
  "request_depth":0,
  "request_duration":0.000623773,
  "error_message": "...",
  "error_class": "...",
  "error_backtrace": "...",
  "tree_path": "BDF",
  "tree_leaf": true
}

Appending data to the request log entry

You can also append arbitrary data to the request log by calling:

# Append structured data (will be merged)
Kiev.payload(first_name: "john", last_name: "smith")

# Same thing
Kiev[:first_name] = "john"
Kiev[:last_name] = "smith"

Other events

Kiev allows you to log custom events as well.

The recommended way to do this is by using the #event method:

# Log event without any data
Kiev.event(:my_event)

# Log structured data (will be merged)
Kiev.event(:my_event, { some_array: [1, 2, 3] })

# Log other data types (will be available under the `message` key)
Kiev.event(:my_event, "hello world")

However, Kiev.logger implements the Ruby Logger class, so all the other methods are available as well:

Kiev.logger.info("hello world")
Kiev.logger.debug({ first_name: "john", last_name: "smith" })

Note that, even when logging custom events, Kiev will try to append request information to the entries: the HTTP verb and path for web request or job_name and jid for background jobs. The payload, however, will be logged only for the request_finished or job_finished events. If you want to add a payload to a custom event, use the second argument of the event method.

Advanced configuration

development_mode

Kiev offers human-readable logging for development purposes. You can enable it via the development_mode option:

Kiev.configure do |config|
  config.development_mode = Rails.env.development?
end

filtered_params

By default, Kiev filters out the values for the following parameters:

client_secret
token
password,
password_confirmation
old_password
credit_card_number
credit_card_cvv

You can override this behaviour via the filtered_params option:

Kiev.configure do |config|
  config.filtered_params = %w(email first_name last_name)
end

ignored_params

By default, Kiev ignores the following parameters:

controller
action
format
authenticity_token
utf8

You can override this behaviour via the ignored_params option:

Kiev.configure do |config|
  config.ignored_params = %w(some_field some_other_field)
end

log_request_condition

By default, Kiev doesn't log requests to /ping or /health or requests to assets.

You can override this behaviour via the log_request_condition option, which should be a proc returning a boolean:

Kiev.configure do |config|
  config.log_request_condition = proc do |request, response|
    !%r{(^(/ping|/health))|(\.(js|css|png|jpg|gif)$)}.match(request.path)
  end
end

log_request_error_condition

Kiev logs Ruby exceptions. By default, it won't log the exceptions produced by 404s.

You can override this behaviour via the log_request_error_condition option, which should be a proc returning a boolean:

Kiev.configure do |config|
  config.log_request_error_condition = proc do |request, response|
    response.status != 404
  end
end

log_response_body_condition

Kiev can log the response body. By default, it will only log the response body when the status code is in the 4xx range and the content type is JSON or XML.

You can override this behaviour via the log_response_body_condition option, which should be a proc returning a boolean:

Kiev.configure do |config|
  config.log_response_body_condition = proc do |request, response|
    response.status >= 400 && response.status < 500 && response.content_type =~ /(json|xml)/
  end
end

persistent_log_fields

If you need to log some data for every event in the session (e.g. the user ID), you can do this via the persistent_log_fields option.

Kiev.configure do |config|
  config.persistent_log_fields = [:user_id]
end

# Somewhere in application
before do
  Kiev[:user_id] = current_user.id
end

get "/" do
  "hello world"
end

nginx

If you want to log 499 and 50x errors in nginx, which will not be captured by Ruby application, consider adding this to your nginx configuration:

log_format kiev '{"application":"app_name", "event":"request_finished",'
  '"timestamp":"$time_iso8601", "request_id":"$http_x_request_id",'
  '"user_agent":"$http_user_agent", "status":$status,'
  '"request_duration_seconds":$request_time, "host":"$host",'
  '"verb":"$request_method", "path":"$request_uri", "tree_path": "$http_x_tree_path"}';

log_format simple_log '$remote_addr - $remote_user [$time_local] '
                       '"$request" $status $bytes_sent '
                       '"$http_referer" "$http_user_agent"';

map $status $not_loggable {
  ~(499) 0;
  default 1;
}

map $status $loggable {
  ~(499) 1;
  default 0;
}

server {
  access_log /var/log/nginx/access.kiev.log kiev if=$loggable;
  access_log /var/log/nginx/access.log simple_log if=$not_loggable;

  location = /50x.html {
    access_log /var/log/nginx/access.kiev.log kiev;
  }
}

If you'd like to measure nginx queue latency, add the following to your nginx configuration:

server {
  ...
  proxy_set_header X-Request-Start "${msec}";
  ...
}

Other libs/technologies using X-Request-Start are rack-timeout and NewRelic. There's no support for ELB :(

Logstash, Logrotate, Filebeat

Kiev does not provide facilities to log directly to ElasticSearch. This is done for simplicity. Instead we recommend using Filebeat to deliver logs to ElasticSearch.

When storing logs on disk, we recommend using Logrotate in truncate mode.

You can use jq to traverse JSON log files, when you're not running Kiev in development mode.

Suffixing `tree_path`

Kiev is built upon the assumption that one request is handled once. This isn't always true.

A practical example: multiple Amazon SQS queues subscribed to one Amazon SNS topic. You send one message to SNS and queues receive identical copies that are impossible to distinguish in the trace without any help from the outside.

You can solve this by adding a fixed unique suffix inside each queue processor. Preferably a single character with an even number in the alphabet (B, D, F and so on), to maintain the notion of "asynchronous processing" used throughout Kiev.

For a combination of SNS and Shoryuken (SQS consumer). Here's how you can use it:

Enable "Raw Message Delivery" in your SQS-to-SNS subscriptions
On sender, write Kiev::SubrequestHelper.payload into the message attributes
On each receiver, use Kiev::Shoryuken::suffix_tree_path with a unique tag, like this:

  # Suffix a single worker class:
  class MyWorker
    include Shoryuken::Worker
    Kiev::Shoryuken.suffix_tree_path(self, "B")
    # ...
  end

  # Or use a suffix process-wide:
  Shoryuken.configure_server do |config|
    Kiev::Shoryuken.suffix_tree_path(config, "B")
  end

Here's an example of the possble tree_path sequence you could get by configuring two consumers with suffixes 1 and 2 (note ordering by tree_path):

`tree_path`	Meaning
`A`	An entry point into the system, a synchronous request
`AB`	Background job caused by `A` executed
`ABA`	Synchoronous request made from `AB`
`ABD`	(Not logged by Kiev itself) `AB` sends out an SNS message
`ABD1`	Message `ABD` handled by susbcriber `1`
`ABD1A`	Synchronous request sent by `1` when handling the message `ABD`
`ABD1C`	Synchronous request sent by `1` when handling the message `ABD`
`ABD2`	Message `ABD` handled by susbcriber `2`
`ABD2A`	Synchronous request sent by `2` when handling the message `ABD`
`ABF`	Another backgound job from `AB` executed
`AD`	Background job caused by `A` executed
`AE`	Synchronous request made from `A`

Without suffixing you won't see at a glance who made the request ABDC and you will have two entries for both ABD and ABDA. As different subscribers may log different fields, you might be able to tell apart ABDs. But both ABDAs could happen on the same node and be logged with the same lines of code.

Alternatives

Logging

Request-Id

Development

Pull the code:

git clone git@github.com:blacklane/kiev.git

Run tests:

bundle exec rake

Run tests for different rubies, frameworks and framework versions:

# Create a Postgres test database for Que
createdb que_test

# Run the tests (replace myuser with your username)
DATABASE_URL=postgres://myuser:@localhost/que_test bundle exec wwtd

Kiev

Install

Configure

Rails

Sinatra

Rack

Hanami

Sidekiq

Shoryuken

Que

Her

Loading only the required parts

Logging

Requests

Background jobs

Appending data to the request log entry

Other events

Advanced configuration

development_mode

filtered_params

ignored_params

log_request_condition

log_request_error_condition

log_response_body_condition

persistent_log_fields

nginx

Logstash, Logrotate, Filebeat

Suffixing tree_path

Alternatives

Logging

Request-Id

Development

Suffixing `tree_path`