GOAPI

Table of Contents

• Summary
• Demo
• Technologies Used
• Building
• Running
• Library Usage
• Extending the API

Summary

This golang library is a framework for implementing an API server. The statically-linked all-in-one CLI binary built by this project may run as either the client or the server, depending on the command line arguments.

The API server responds to both GRPC and JSON REST requests. The framework also includes an /auth endpoint which responds with JWT auth tokens, middleware that enforces authentication, a user database, SSL encryption, and other standard requirements for any API server.

The example client and server implementation demonstrates a key/value store, which is only available to authenticated users.

An example project that uses this library may be found at: goapi-example

Demo

Technologies Used

The goapi library uses GRPC and grpc-gateway, which allows us to code-generate API service and client libraries. Alternative golang API frameworks to GRPC/GW include API toolkits such as Gin or Gorilla. GRPC is nice to use because of code-generation.

This project provides:

• An API server implementation which responds to requests over GRPC protocol buffers as well as JSON Rest. All JSON Rest requests are proxied over grpc-gateway to the GRPC server.
• Code-generation capabilities for API service and client libraries, as described by protocol buffers .proto service description file.
• A cobra CLI tool with subcommands that can launch the API server as well as drive the API as a CLI client. The CLI tool stores its settings in viper configuration.
• A Makefile which generates code resources including:
  • GRPC code files including protobuf, grpc, grpc-gateway, swagger
  • SSL certs using cfssl
  • Swagger asset files with embedded swagger-ui, to serve the swagger file
  • Cross-compiling statically linked Linux binaries for amd64 and armv7.
• A test framework using ginkgo and gomega matchers
• Provides an /auth endpoint which returns a JWT token when presented with valid credentials. This authentication system is based on JWT.
• An Role Based Access Control authorization system.
• A structured logging system using logrus
• The tools to code-generate the API framework from services and endpoints
• A basic user database
• An example key/value API service for storing values to sqlite.

Building

• To print Makefile usage, run make
• To build everyting run make all

$ make
all                            run all targets
cert_gen                       generate go-bindata cert files
check                          checks
clean                          delete all non-repo files
code_gen                       generate grpc go files from proto spec
compile                        build the binaries for amd64
compilex                       build the binaries for all platforms
demo                           run and record the demo-magic script
deps                           install host dependencies
resource_gen                   generate go-bindata swagger files
vendor                         install/build all 3rd party vendor libs and bins
help                           Print list of Makefile targets

Running

# Show Usage
goapi

# Start the GRPC+JSON server on port 10080
goapi server

### Use the GRPC CLI Client

# Obtain an Auth Token
goapi auth login

# Create a Key
goapi keyval create mykey myval

# Read a Key
goapi keyval read mykey

# Update a Key
goapi keyval update mykey myval2

# Delete a Key
goapi keyval delete mykey

### Use Curl

# Obtain an Auth Token
TOKEN=$(curl -fsSL -X POST -k https://localhost:10080/v1/auth -H "Content-Type: text/plain" -d '{"grant_type": "password", "username": "admin", "password": "password"}' | jq --raw-output '.access_token')

# Create a Key
curl -k -X PUT    https://localhost:10080/v1/keyval/mykey -H "Content-Type: text/plain" -H "Authorization: Bearer $TOKEN" -d '{"value": "myval1"}'

# Read a Key
curl -k -X GET    https://localhost:10080/v1/keyval/mykey -H "Content-Type: text/plain" -H "Authorization: Bearer $TOKEN"

# Update a Key
curl -k -X POST   https://localhost:10080/v1/keyval/mykey -H "Content-Type: text/plain" -H "Authorization: Bearer $TOKEN" -d '{"value": "myval2"}'

# Delete a Key
curl -k -X DELETE https://localhost:10080/v1/keyval/mykey -H "Content-Type: text/plain" -H "Authorization: Bearer $TOKEN"

### View the Swagger UI

# View the swagger-ui
curl -k https://localhost:10080/swagger-ui/

# View the swagger file that has been generated from GRPC
curl -k https://localhost:10080/swagger.json

Library Usage

To use this project as a library, here are the instructions

• Copy some of the contents of this project to to your own project

# Assuming you are already in your new project root directory

GOAPI_PATH=/go/src/github.com/dcwangmit01/goapi

cp -r ${GOAPI_PATH}/example/* .
cp -r ${GOAPI_PATH}/go.* .
cp -r ${GOAPI_PATH}/main.go .
cp -r ${GOAPI_PATH}/Makefile .
cp -r ${GOAPI_PATH}/scripts .
cp -r ${GOAPI_PATH}/.gitignore .
cp -r ${GOAPI_PATH}/demo .
cp -r ${GOAPI_PATH}/vendor.go .

cp -r ${GOAPI_PATH}/cfssl .
make -C cfssl mrclean # we'll regenerate the cert files later

mkdir -p ./resources/certs
cp -r ${GOAPI_PATH}/resources/certs/config.go ./resources/certs

Then, do the following edits:

• Edit go.mod to set github.com/YOUR_GITHUB_ID/YOUR_PROJECT.
• Edit Makefile and delete all targets and references starting with example/.
• Rewrite the imports with: sed -i 's@dcwangmit01/goapi/example@YOUR_GITHUB_ID/YOUR_PROJECT@' $(make gosources)
• Rewrite certs imports with: sed -i 's@dcwangmit01/goapi/resources/certs@YOUR_GITHUB_ID/YOUR_PROJECT/resources/certs@' $(make gosources)
• Include goapi as a go dependency go get -u github.com/dcwangmit01/goapi

Note: Much of the above can be streamlined given time and effort.

Extending the API

To extend the api, edit any the .proto files to add additional Protobuf messages as well as services. There is a common proto file in the library pb/goapi.proto as well as a proto file in the example example/pb/app.proto.

Here's how to extend the examples API

# Edit the .proto files to add messages as well as services
#   As example, consider you create a new Tasklist service
<your_fav_editor> example/pb/app.proto

# Update the code-generated files (*.pb.go, *pb.gw.go)
make code_gen

# Create an implementation of the new TasklistServer interface that you've
#   defined in the .proto file, which has been auto-generated for you in the
#   *.pb.go file.  Follow the existing keyval example.
<your_fav_editor> example/service/tasklist.go

# Add a subcommand to the CLI tool that can drive the new Tasklist service.
#   This subcommand will call the TasklistClient that has been auto-generated
#   for you in the *.pb.go file.  Follow the existing keyval example.
<your_fav_editor> example/cmd/tasklist.go