Rails <> OpenTelemetry Logs

[adenta]

@kaylareopelle check out the rails logs integration I put together:

# frozen_string_literal: true

require 'opentelemetry-logs-sdk'
require 'opentelemetry/exporter/otlp_logs'

module Loggers
  class OtelLogger < Logger
    def initialize(logdev)
      super
      setup_opentelemetry
    end

    private

    def setup_opentelemetry
      # Create a LoggerProvider
      logger_provider = OpenTelemetry::SDK::Logs::LoggerProvider.new

      # Create a batching processor configured to export to the OTLP exporter
      processor = OpenTelemetry::SDK::Logs::Export::BatchLogRecordProcessor.new(
        OpenTelemetry::Exporter::OTLP::Logs::LogsExporter.new(endpoint: "#{ENV['OTEL_EXPORTER_OTLP_ENDPOINT']}/v1/logs")
      )

      # Add the processor to the LoggerProvider
      logger_provider.add_log_record_processor(processor)

      # Access a Logger for your library from your LoggerProvider
      @otel_logger = logger_provider.logger(name: Rails.application.class.module_parent_name)

      # Ensure the logger provider is properly shut down when the application exits
      at_exit { logger_provider.shutdown }
    end

    def format_message(severity, datetime, progname, msg)
      @otel_logger.on_emit(
        timestamp: datetime,
        severity_text: severity,
        body: msg.to_s
        # attributes: { 'progname' => progname }
      )
      super
    end
  end
end

This is nice because it only needs a single line of config in production.rb to get logs flowing to OTEL:
config.logger = Loggers::OtelLogger.new(STDOUT)

[kaylareopelle]

Hi @adenta! Thanks for sharing your example! I think this could be a good candidate for a Rails logger bridge distributed within the open-telemetry/opentelemetry-ruby-contrib repo.

One option to distribute it would be to create a new gem, maybe opentelemetry-bridge-rails-logger or opentelemetry-instrumentation-rails-logger. We have an instrumentation contributor's guide. It describes, among other things, our instrumentation generator that can be used to help set up the general structure of any new contrib gems to match our other gems.

Since this is so lightweight, it might be that adding something to the existing opentelemetry-instrumentation-rails gem may be more appropriate than creating an entirely new gem. It has a Railtie that defines an initializer and configures the SDK. Maybe the logger bridge would fit here too?

We haven't released any logs bridges yet, so we're open to brainstorming together on the best way to distribute this code.

[seuros]

To keep consistent with Rails default
config.logger = ActiveSupport::TaggedLogging.new(Loggers::OtelLogger.new($stdout))

[tomash]

I like it! The only thing it needs is using OTEL_EXPORTER_OTLP_HEADERS.

[fguillen]

Hi @adenta thanks for sharing this code snippet. I am trying to integrate my Rails app with Otel_collector and the only missing piece is Logs. I don't find any documentation of how to do the integration (no README in the library).

Checking your code, it is not clear to me how to use the defined Loggers module.

I am using lograge to format the logs. But I can use any other thing if this makes things easier to integration with Otel_collector