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AWS Distro for OpenTelemetry Ruby - Sample App - Manual instrumentation - Ruby on Rails

This application validates the continual integration of manual instrumentation with the AWS Distro for OpenTelemetry Ruby and the AWS X-Ray back-end service. Validation is done using the AWS Test Framework for OpenTelemetry.

Application interface

The application uses Ruby on Rails to expose the following routes:

  1. /
    • Ensures the application is running.
  2. /outgoing-http-call
    • Makes a HTTP request to aws.amazon.com.
  3. /aws-sdk-call
    • Makes a call to AWS S3 to list buckets for the account corresponding to the provided AWS credentials.

Requirements

  • Ruby 2.7+
  • Rails 7.0+

While this example requires Ruby 2.7+, the OpenTelemetry Ruby documentation indicates compatibility with versions of Ruby 2.5 and higher.

Running the application

For more information on running a ruby application using manual instrumentation, please refer to the ADOT Ruby Manual Instrumentation Documentation. In this context, the ADOT Collector is being run locally as a sidecar.

Use LISTEN_ADDRESS=127.0.0.1:8080 rails server to run the application directly in your terminal.

Sending metrics to Amazon CloudWatch is not yet validated. Check out the OpenTelemetry Features Status Page to learn more about timelines for metrics.

Application structure

This section describes the decisions made when designing the sample apps instrumented with ADOT Ruby.

A minimal app

Although this app was created with the rails new ruby-on-rails --minimal command, it has been even further stripped down to focus on the OpenTelemetry changes needed to get tracing in this ruby on rails app.

The changes needed to trace with OpenTelemetry are found in sample-apps/manual-instrumentation/ruby-on-rails/config/initializers/opentelemetry.rb.

Running the app in production for tests

We build our application for a production environment because of #10.

However, to allow for a production environment, the rails app requires a "secret_base_key". Otherwise it will flood the log output with warnings thereby hiding useful logs.

To solve this, we added dummy credentials which don't do anything. Because this is an example, we directly commit the security credentials in the Dockerfile but this is NOT GOOD PRACTICE FOR REAL PRODUCTION ENVIRONMENTS. We allow it to be like this because we want this demo to work out-of-the-box for any public user.

You can confirm the credentials work and view the encrypted contents of the sample app by doing the following command:

$ cd sample-apps/manual-instrumentation/ruby-on-rails
$ RAILS_MASTER_KEY=<KEY_IN_SAMPLE-APP_DOCKERFILE> bin/rails credentials:edit

This will show the following contents:

# NOTE: DO NOT USE THIS IN PRODUCTION ENVIRONMENTS, WE ONLY SET THIS TO SIMULATE A REAL RAILS APP.

# Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.
secret_key_base: DO_NOT_STORE_A_SECRET_THIS_IS_JUST_FOR_AN_EXAMPLE

We cannot use something like RAILS_MASTER_KEY=DUMMY_KEY because the rails app would fail to start in the test with the following message:

app_1 | 2022-02-04 22:18:51 +0000 Rack app ("GET /outgoing-http-call" - (172.18.0.4)): #<ActiveSupport::MessageEncryptor::InvalidMessage: ActiveSupport::MessageEncryptor::InvalidMessage>