Instrumenting Ruby Serverless Applications Using the Datadog Forwarder

Overview

If you are a new user of Datadog Serverless, follow the instructions to instrument your Lambda functions using the Datadog Lambda Extension instead. If you have setup Datadog Serverless with the Datadog Forwarder before Lambda offered out-of-the-box functionality, use this guide to maintain your instance.

Prerequisites

The Datadog Forwarder Lambda function is required to ingest AWS Lambda traces, enhanced metrics, custom metrics, and logs.

Configuration

    The Datadog CLI modifies existing Lambda functions’ configurations to enable instrumentation without requiring a new deployment. It is the quickest way to get started with Datadog’s serverless monitoring.

    You can also add the command to your CI/CD pipelines to enable instrumentation for all your serverless applications. Run the command after your normal serverless application deployment, so that changes made by the Datadog CLI command are not overridden.

    Install

    Install the Datadog CLI with NPM or Yarn:

    # NPM
npm install -g @datadog/datadog-ci

# Yarn
yarn global add @datadog/datadog-ci

    Instrument

    To instrument the function, run the following command with your AWS credentials.

    datadog-ci lambda instrument -f <functionname> -f <another_functionname> -r <aws_region> -v <layer_version> --forwarder <forwarder_arn>

    To fill in the placeholders:

    • Replace <functionname> and <another_functionname> with your Lambda function names.
    • Replace <aws_region> with the AWS region name.
    • Replace <layer_version> with the desired version of the Datadog Lambda Library. The latest version is 22.
    • Replace <forwarder_arn> with the Forwarder ARN (see the Forwarder documentation).

    For example:

    datadog-ci lambda instrument -f my-function -f another-function -r us-east-1 -v 22 --forwarder "arn:aws:lambda:us-east-1:000000000000:function:datadog-forwarder"

    If your Lambda function is configured to use code signing, you must add Datadog’s Signing Profile ARN (arn:aws:signer:us-east-1:464622532012:/signing-profiles/DatadogLambdaSigningProfile/9vMI9ZAGLc) to your function’s Code Signing Configuration before you can instrument it with the Datadog CLI.

    More information and additional parameters can be found in the CLI documentation.

    The Datadog Serverless Plugin automatically adds the Datadog Lambda library to your functions using layers, and configures your functions to send metrics, traces, and logs to Datadog through the Datadog Forwarder.

    If your Lambda function is configured to use code signing, you must add Datadog’s Signing Profile ARN (arn:aws:signer:us-east-1:464622532012:/signing-profiles/DatadogLambdaSigningProfile/9vMI9ZAGLc) to your function’s Code Signing Configuration before you install the Datadog Serverless Plugin.

    To install and configure the Datadog Serverless Plugin, follow these steps:

    1. Install the Datadog Serverless Plugin:
      yarn add --dev serverless-plugin-datadog
    2. In your serverless.yml, add the following:
      plugins:
  - serverless-plugin-datadog
    3. In your serverless.yml, also add the following section:
      custom:
  datadog:
    forwarderArn: # The Datadog Forwarder ARN goes here.
      More information on the Datadog Forwarder ARN or installation can be found here. For additional settings, see the plugin documentation.

    Install

    The Datadog Lambda Library can be installed as a layer or a gem. For most functions, Datadog recommends installing the library as a layer. If your Lambda function is deployed as a container image, you must install the library as a gem.

    The minor version of the datadog-lambda gem always matches the layer version. For example, datadog-lambda v0.5.0 matches the content of layer version 5.

    Using the layer

    Configure the layers for your Lambda function using the ARN in the following format.

    # For us,us3,us5,eu regions
arn:aws:lambda:<AWS_REGION>:464622532012:layer:Datadog-<RUNTIME>:<VERSION>

# For us-gov regions
arn:aws-us-gov:lambda:<AWS_REGION>:002406178527:layer:Datadog-<RUNTIME>:<VERSION>

    The available RUNTIME options are Ruby2-7, and Ruby3-2. The latest VERSION is 22. For example:

    arn:aws:lambda:us-east-1:464622532012:layer:Datadog-Ruby3-2:22

    If your Lambda function is configured to use code signing, you must add Datadog’s Signing Profile ARN (arn:aws:signer:us-east-1:464622532012:/signing-profiles/DatadogLambdaSigningProfile/9vMI9ZAGLc) to your function’s Code Signing Configuration before you can add the Datadog Lambda library as a layer.

    Using the gem

    If you cannot use the prebuilt Datadog Lambda layer, you can add the following to your Gemfile as an alternative:

    gem 'datadog-lambda'
gem 'ddtrace'

    ddtrace contains native extensions that must be compiled for Amazon Linux to work with AWS Lambda. Datadog therefore recommends that you build and deploy your Lambda as a container image. If your function cannot be deployed as a container image and you would like to use Datadog APM, Datadog recommends installing the Lambda Library as a layer instead of as a gem.

    Install gcc, gmp-devel, and make prior to running bundle install in your function’s Dockerfile to ensure that the native extensions can be successfully compiled.

    FROM <base image>

# assemble your container image

RUN yum -y install gcc gmp-devel make
RUN bundle config set path 'vendor/bundle'
RUN bundle install

    Configure

    Enable Datadog APM and wrap your Lambda handler function using the wrapper provided by the Datadog Lambda library.

    require 'datadog/lambda'

Datadog::Lambda.configure_apm do |c|
# Enable the instrumentation
end

def handler(event:, context:)
    Datadog::Lambda.wrap(event, context) do
        return { statusCode: 200, body: 'Hello World' }
    end
end

    Subscribe

    Subscribe the Datadog Forwarder Lambda function to each of your function’s log groups. This enables sending metrics, traces, and logs to Datadog.

    1. Install the Datadog Forwarder if you haven’t.
    2. Subscribe the Datadog Forwarder to your function’s log groups.

    Tag

    Although it’s optional, Datadog recommends tagging you serverless applications with the env, service, and version tags following the unified service tagging documentation.

    Explore

    After configuring your function following the steps above, view your metrics, logs, and traces on the Serverless homepage.

    Monitor custom business logic

    If you would like to submit a custom metric or span, see the sample code below:

    require 'ddtrace'
require 'datadog/lambda'

Datadog::Lambda.configure_apm do |c|
# Enable the instrumentation
end

def handler(event:, context:)
    # Apply the Datadog wrapper
    Datadog::Lambda::wrap(event, context) do
        # Add custom tags to the lambda function span,
        # does NOT work when X-Ray tracing is enabled
        current_span = Datadog::Tracing.active_span
        current_span.set_tag('customer.id', '123456')

        some_operation()

        Datadog::Tracing.trace('hello.world') do |span|
          puts "Hello, World!"
        end

        # Submit a custom metric
        Datadog::Lambda.metric(
          'coffee_house.order_value', # metric name
          12.45, # metric value
          time: Time.now.utc, # optional, must be within last 20 mins
          "product":"latte", # tag
          "order":"online" # another tag
        )
    end
end

# Instrument the function
def some_operation()
    Datadog::Tracing.trace('some_operation') do |span|
        # Do something here
    end
end

    For more information on custom metric submission, see Serverless Custom Metrics. For additional details on custom instrumentation, see the Datadog APM documentation for custom instrumentation.

    Further Reading

    Additional helpful documentation, links, and articles: