ddlambda

README

dd-lambda-go

Datadog's Lambda Go client library enables distributed tracing between serverful and serverless environments.

Installation

go get github.com/DataDog/dd-lambda-go

The following Datadog environment variables should be defined via the AWS CLI or Serverless Framework:

• DATADOG_API_KEY
• DATADOG_APP_KEY

Usage

Datadog needs to be able to read headers from the incoming Lambda event. Wrap your Lambda handler function like so:

package main

import (
  "github.com/aws/aws-lambda-go/lambda"
  "github.com/DataDog/dd-lambda-go"
)

func main() {
  // Wrap your lambda handler like this
  lambda.Start(ddlambda.WrapHandler(myHandler, nil))
  /* OR with manual configuration options
  lambda.Start(ddlambda.WrapHandler(myHandler, &ddlambda.Config{
    BatchInterval: time.Seconds * 15
    APIKey: "my-api-key",
    AppKey: "my-app-key",
  }))
  */
}

func myHandler(ctx context.Context, event MyEvent) (string, error) {
  // ...
}

Custom Metrics

Custom metrics can be submitted using the Distribution function. The metrics are submitted as distribution metrics.

ddlambda.Distribution(
  // Context, (ctx), should be the same object passed into your lambda handler function, (or a child).
  // If you don't want to pass the context through your call hierarchy, you can use ddlambda.GetContext()
  ctx,
  "coffee_house.order_value", // Metric name
  12.45, // The value
  "product:latte", "order:online" // Associated tags
)

VPC

If your Lambda function is associated with a VPC, you need to ensure it has access to the public internet.

Distributed Tracing

Distributed tracing allows you to propagate a trace context from a service running on a host to a service running on AWS Lambda, and vice versa, so you can see performance end-to-end. Linking is implemented by injecting Datadog trace context into the HTTP request headers.

Distributed tracing headers are language agnostic, e.g., a trace can be propagated between a Java service running on a host to a Lambda function written in Go.

Because the trace context is propagated through HTTP request headers, the Lambda function needs to be triggered by AWS API Gateway or AWS Application Load Balancer.

To enable this feature, make sure any outbound requests have Datadog's tracing headers.

  req, err := http.NewRequest("GET", "http://api.youcompany.com/status")
  // Use the same Context object given to your lambda handler.
  // If you don't want to pass the context through your call hierarchy, you can use ddlambda.GetContext()
  ddlambda.AddTraceHeaders(ctx, req)

  client := http.Client{}
  client.Do(req)
}

Sampling

The traces for your Lambda function are converted by Datadog from AWS X-Ray traces. X-Ray needs to sample the traces that the Datadog tracing agent decides to sample, in order to collect as many complete traces as possible. You can create X-Ray sampling rules to ensure requests with header x-datadog-sampling-priority:1 or x-datadog-sampling-priority:2 via API Gateway always get sampled by X-Ray.

These rules can be created using the following AWS CLI command.

aws xray create-sampling-rule --cli-input-json file://datadog-sampling-priority-1.json
aws xray create-sampling-rule --cli-input-json file://datadog-sampling-priority-2.json

The file content for datadog-sampling-priority-1.json:

{
  "SamplingRule": {
    "RuleName": "Datadog-Sampling-Priority-1",
    "ResourceARN": "*",
    "Priority": 9998,
    "FixedRate": 1,
    "ReservoirSize": 100,
    "ServiceName": "*",
    "ServiceType": "AWS::APIGateway::Stage",
    "Host": "*",
    "HTTPMethod": "*",
    "URLPath": "*",
    "Version": 1,
    "Attributes": {
      "x-datadog-sampling-priority": "1"
    }
  }
}

The file content for datadog-sampling-priority-2.json:

{
  "SamplingRule": {
    "RuleName": "Datadog-Sampling-Priority-2",
    "ResourceARN": "*",
    "Priority": 9999,
    "FixedRate": 1,
    "ReservoirSize": 100,
    "ServiceName": "*",
    "ServiceType": "AWS::APIGateway::Stage",
    "Host": "*",
    "HTTPMethod": "*",
    "URLPath": "*",
    "Version": 1,
    "Attributes": {
      "x-datadog-sampling-priority": "2"
    }
  }
}

Non-proxy integration

If your Lambda function is triggered by API Gateway via the non-proxy integration, then you have to set up a mapping template, which passes the Datadog trace context from the incoming HTTP request headers to the Lambda function via the event object.

If your Lambda function is deployed by the Serverless Framework, such a mapping template gets created by default.

Opening Issues

If you encounter a bug with this package, we want to hear about it. Before opening a new issue, search the existing issues to avoid duplicates.

When opening an issue, include the Datadog Lambda Layer version, Python version, and stack trace if available. In addition, include the steps to reproduce when appropriate.

You can also open an issue for a feature request.

Contributing

If you find an issue with this package and have a fix, please feel free to open a pull request following the procedures.

License

Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.

This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2019 Datadog, Inc.

Documentation

Index

• Constants
• func AddTraceHeaders(ctx context.Context, req *http.Request)
• func Distribution(metric string, value float64, tags ...string)
• func DistributionWithContext(ctx context.Context, metric string, value float64, tags ...string)
• func GetContext() context.Context
• func GetTraceHeaders(ctx context.Context) map[string]string
• func WrapHandler(handler interface{}, cfg *Config) interface{}
• type Config

Constants

const (
	// DatadogAPIKeyEnvVar is the environment variable that will be used as an API key by default
	DatadogAPIKeyEnvVar = "DATADOG_API_KEY"
	// DatadogAPPKeyEnvVar is the environment variable that will be used as an API key by default
	DatadogAPPKeyEnvVar = "DATADOG_APP_KEY"
)

Functions

func AddTraceHeaders

func AddTraceHeaders(ctx context.Context, req *http.Request)

AddTraceHeaders adds DataDog trace headers to a HTTP Request

func Distribution

func Distribution(metric string, value float64, tags ...string)

Distribution sends a distribution metric to DataDog

func DistributionWithContext

func DistributionWithContext(ctx context.Context, metric string, value float64, tags ...string)

DistributionWithContext sends a distribution metric to DataDog

func GetContext

func GetContext() context.Context

GetContext retrieves the last created lambda context. Only use this if you aren't manually passing context through your call hierarchy.

func GetTraceHeaders

func GetTraceHeaders(ctx context.Context) map[string]string

GetTraceHeaders reads a map containing the DataDog trace headers from a context object.

func WrapHandler

func WrapHandler(handler interface{}, cfg *Config) interface{}

WrapHandler is used to instrument your lambda functions, reading in context from API Gateway. It returns a modified handler that can be passed directly to the lambda.Start function.

Types

type Config

type Config struct {
	// APIKey is your Datadog API key. This is used for sending metrics.
	APIKey string
	// AppKey is your Datadog App key. This is used for sending metrics.
	AppKey string
	// ShouldRetryOnFailure is used to turn on retry logic when sending metrics via the API. This can negatively effect the performance of your lambda,
	// and should only be turned on if you can't afford to lose metrics data under poor network conditions.
	ShouldRetryOnFailure bool
	// BatchInterval is the period of time which metrics are grouped together for processing to be sent to the API or written to logs.
	// Any pending metrics are flushed at the end of the lambda.
	BatchInterval time.Duration
}

Config gives options for how ddlambda should behave