Ruby OpenTelemetry auto-instrumentation

Obtaining telemetry data from applications written in Ruby has never been easier. Thanks to Opentelemetry-Ruby the instrumentation process is very simple. Enabling auto-instrumentation requires you to perform three steps, explained in detail below. First, installation of the required gems, which hold the OpenTelemetry SDK and library-specific instrumentation. Second, code changes required for instrumentation enable and lastly, the exporter configuration.

How to instrument your Ruby application?

There are a few simple steps to instrument the application and export the telemetry data by OpenTelemetry Protocol exporter - version sdk=1.5.0, exporter=0.28.1.

Step 1. Gems Installation

Installation of the packages listed below is required to apply the instrumentation and export telemetry data. All listed gems are located on RubyGems.org and they can be installed in two different ways:

• gem command

  gem install opentelemetry-sdk -v 1.5.0
  gem install opentelemetry-exporter-otlp -v 0.28.1

• bundler, the packages have to be inserted into your gemfile and bundle install command has to be run

  gem 'opentelemetry-sdk', '1.5.0'
  gem 'opentelemetry-exporter-otlp', '0.28.1'

Installation of the gems above is mandatory. The next step is to install instrumentation packages corresponding to the libraries used in the application. A complete list of available plugins can be found here.

There are two solutions:

• Installation of the specific packages - for example, if the application is a Sinatra HTTP server which is also performing some HTTP requests using Net HTTP package. To instrument all the incoming and outgoing requests corresponding instrumented packages have to be installed:

  gem install opentelemetry-instrumentation-sinatra -v 0.24.1
  gem install opentelemetry-instrumentation-net_http -v 0.22.7

• Installation of the “all in one” package - installing this package will install all available instrumentation packages:

  gem install opentelemetry-instrumentation-all -v 0.62.1

Step 2. Required code changes

To enable instrumentation in the application and export the telemetry data it is enough to add the code below to the project. Two examples below present a specific package and an “all in one” instrumentation. 

• Specific package instrumentation - in this example only Sinatra and Net HTTP libraries will be instrumented.

  require 'opentelemetry/sdk'
  Bundler.require
  OpenTelemetry::SDK.configure do |c|
     c.use 'OpenTelemetry::Instrumentation::Sinatra'
     c.use 'OpenTelemetry::Instrumentation::Net::HTTP'
  end

• "All in one" instrumentation - this configuration will instrument all available package:

  require 'opentelemetry/sdk'
  Bundler.require
  OpenTelemetry::SDK.configure do |c|
     c.use_all
  end

Step 3. Telemetry data exporter configuration

The final step is to configure the exporter host and service name. This can be done directly in the code or by environment variables. In this example, the exporter will be configured by environment variables.

• Environment variable sets the exporter to OTLP:

  OTEL_EXPORTER=otlp

• Environment variable configures the endpoint where telemetry data will be sent:

  OTEL_EXPORTER_OTLP_ENDPOINT=http://OTLP_ENDPOINT:4318

  This should be OpenTelemetry Collector/Agent endpoint address or OTLP/HTTP source. For Kubernetes environments, see the available endpoints for a direct connection. For other environments see endpoints and protocols.

• Configure the service name. Ensure the string value represents its business logic, such as FinanceServiceCall.  This will appear as a tracing service name in Sumo Logic.

  OTEL_SERVICE_NAME=SERVICE_NAME

• Configure the application name. This will appear as a tracing application name in Sumo Logic. Additional attributes can be added here as comma separated key=value pairs:

  OTEL_RESOURCE_ATTRIBUTES=application=APPLICATION_NAME

TraceID, SpanID and operation data injection into logs

Additional information like TraceID, SpanID or operation data in the application logs could be very helpful to correlate traces, spans and operations with specific logs. To add this data to the logs it is required to obtain it from OpenTelemetry::Trace and modify logger.

Please see example code:

logger = ::Logger.new(STDOUT)
logger.formatter = proc do |severity, time, progname, msg|
  span_id = OpenTelemetry::Trace.current_span.context.hex_span_id
  trace_id = OpenTelemetry::Trace.current_span.context.hex_trace_id
  if defined? OpenTelemetry::Trace.current_span.name
    operation = OpenTelemetry::Trace.current_span.name
  else
    operation = 'undefined'
  end

  "#{time}, #{severity}: #{msg} - trace_id=#{trace_id} - span_id=#{span_id} - operation=#{operation}\n"
end
set :logger, logger

Example output:

"2022-02-28 13:01:25 +0000, INFO: {:remote_ip\>\"127.0.0.6\", :request_path\>\"/get_beans\", :query_string\>\"\", :request_method\>\"POST\", :execution_time_sec\>0.00033453479409217834, :response_status_code\>200} - trace_id=cdd460d538917f82560cbb91373a05a6 - span_id=12a09921c89fd6e9 - operation=POST /get_beans