go

Golang utilities and packages

Packages

• aws/cloudmap/resolver - Cloud Map custom resolver for Go
  • aws/cloudmap/resolver/grpc gRPC resolver that implements grpc/resolver.Resolver
  • awsutil/detector - Detects the compute type

aws/cloudmap/resolver/grpc

Package grpc implements a Cloud Map resolver. It sends the target name without scheme back to gRPC as resolved address.

Based upon google.golang.org/grpc/resolver

Installation

With Go module support (Go 1.11+), simply add the following import

import (
    cloudmap "github.com/buzzsurfr/go/aws/cloudmap/resolver/grpc"
)

to your code, and then go [build|run|test] will automatically fetch the necessary dependencies.

Otherwise, to install the package, run the following command:

go get -u github.com/buzzsurfr/go/aws/cloudmap/resolver/grpc

Usage

per-gRPC connection

To add the resolver to a grpc Dial call, ensure the hostname specifies the scheme awscloudmap:///, matches the Cloud Map service and namespace, and use the WithResolvers() function:

grpc.WithResolvers(cloudmap.NewBuilder())

For example, the gRPC connection accepts the WithResolvers() funcdtion as a parameter. The connection string looks like:

conn, err := grpc.Dial("awscloudmap:///service.namespace[:port]", grpc.WithResolvers(cloudmap.NewBuilder()))

Default resolver

The Cloud Map resolver registers itself as an available scheme named awscloudmap and can be set to the default by calling the SetDefaultScheme() function in your init function. If you set the default scheme to awscloudmap, then you do not need to include the scheme in your hostname, but ALL requests for that application will go to Cloud Map by default.

func init() {
  grpc.SetDefaultScheme("awscloudmap")
}

AWS X-Ray integration

The Cloud Map resolver supports AWS X-Ray for sending traces used by the resolver.

The Builder supports a functional option WithContext() where the context can be passed into the package from the main program. The context is necessary in order for the xray package to identify the TraceID.

X-Ray needs to be integrated into your application. To do so, start a segment at the beginning of your program.

xrayCtx, seg := xray.BeginSegment(context.Background(), "Segment Name")
defer seg.Close(nil)

Since the resolver is loaded at init time, adding X-Ray integration requires creating and overriding the existing resolver. Create the custom resolver with the context, then call grpc.Dial using WithResolvers() option.

customResolver := cloudmap.NewBuilder(cloudmap.WithContext(xrayCtx))
conn, err := grpc.Dial("awscloudmap:///service.namespace[:port]", grpc.WithInsecure(), grpc.WithBlock(), grpc.WithResolvers(customResolver))

awsutil/detector

Package detector detects the compute type, supporting the following compute types (in this order):

• AWS Lambda
• Amazon ECS
• Amazon EKS
• Kubernetes
• Docker
• Amazon EC2

The Detect function returns a DetectOutput type which does support casting the type to a string as well as boolean check functions (either as functions or methods):

• IsLambda
• IsECS
• IsEKS
• IsKubernetes
• IsDocker
• IsEC2

Example

import "detector"

func main() {
  fmt.Println(detector.Detect())
}