Go HTTP router library for AWS API Gateway-invoked Lambda Functions
Full credit to aquasecurity for developing the router library for the AWS REST API (V1)
lmdrouterv2 is a simple-to-use library for writing AWS Lambda functions in Go
that listen to events of type API Gateway Proxy Request. It allows creating a
lambda function that can match requests based on their URI, just like an HTTP
server would.
The library provides an interface not unlike the standard net/http.Mux type
or community libraries such as httprouter
and chi.
When building large cloud-native applications, there's a certain balance to strike when it comes to deployment of APIs. On one side of the scale, each API endpoint has its own lambda function. This provides the greatest flexibility, but is extremely difficult to maintain. On the other side of the scale, there can be one lambda function for the entire API. This provides the least flexibility, but is the easiest to maintain. Both are probably not a good idea.
With lmdrouter, one can create small lambda functions for different aspects of
the API. For example, if your application model contains multiple domains (e.g.
articles, authors, topics, etc...), you can create one lambda function for each
domain, and deploy these independently (e.g. everything below "/api/articles" is
one lambda function, everything below "/api/authors" is another function). This
is also useful for applications where different teams are in charge of different
parts of the API.
- Supports all HTTP methods.
- Supports middleware at a global and per-resource level.
- Supports path parameters with a simple ":" format (e.g. "/posts/:id").
- Provides ability to automatically "unmarshal" an API Gateway request to an arbitrary Go struct, with data coming either from path and query string parameters, or from the request body (only JSON requests are currently supported).
- Provides ability to automatically "marshal" responses of any type to an API Gateway response (only JSON responses are currently generated).
This is a very early, alpha release. API is subject to change.
go get github.com/shodgson/lmdrouterv2lmdrouterv2 is meant to be used inside Go Lambda functions.
package main
import (
"github.com/aws/aws-lambda-go/lambda"
"github.com/shodgson/lmdrouterv2"
)
var router *lmdrouterv2.Router
func init() {
router = lmdrouterv2.NewRouter("/api", loggerMiddleware, authMiddleware)
router.Route("GET", "/", listSomethings)
router.Route("POST", "/", postSomething, someOtherMiddleware)
router.Route("GET", "/:id", getSomething)
router.Route("PUT", "/:id", updateSomething)
router.Route("DELETE", "/:id", deleteSomething)
}
func main() {
lambda.Start(router.Handler)
}
// the rest of the code is a redacted example, it will probably reside in a
// separate package inside your project
type listSomethingsInput struct {
ID string `lambda:"path.id"` // a path parameter declared as :id
ShowSomething bool `lambda:"query.show_something"` // a query parameter named "show_something"
AcceptedLanguages []string `lambda:"header.Accept-Language"` // a multi-value header parameter
}
type postSomethingInput struct {
Title string `json:"title"`
Date time.Time `json:"date"`
}
func listSomethings(ctx context.Context, req events.APIGatewayV2HTTPRequest) (
res events.APIGatewayProxyResponse,
err error,
) {
// parse input from request and path parameters
var input listSomethingsInput
err = lmdrouterv2.UnmarshalRequest(req, false, &input)
if err != nil {
return lmdrouterv2.HandleError(err)
}
// call some business logic that generates an output struct
// ...
return lmdrouterv2.MarshalResponse(http.StatusOK, nil, output)
}
func postSomethings(ctx context.Context, req events.APIGatewayV2HTTPRequest) (
res events.APIGatewayProxyResponse,
err error,
) {
// parse input from request body
var input postSomethingsInput
err = lmdrouterv2.UnmarshalRequest(req, true, &input)
if err != nil {
return lmdrouterv2.HandleError(err)
}
// call some business logic that generates an output struct
// ...
return lmdrouterv2.MarshalResponse(http.StatusCreated, nil, output)
}
func loggerMiddleware(next lmdrouterv2.Handler) lmdrouterv2.Handler {
return func(ctx context.Context, req events.APIGatewayV2HTTPRequest) (
res events.APIGatewayProxyResponse,
err error,
) {
// [LEVEL] [METHOD PATH] [CODE] EXTRA
format := "[%s] [%s %s] [%d] %s"
level := "INF"
var code int
var extra string
res, err = next(ctx, req)
if err != nil {
level = "ERR"
code = http.StatusInternalServerError
extra = " " + err.Error()
} else {
code = res.StatusCode
if code >= 400 {
level = "ERR"
}
}
log.Printf(format, level, req.HTTPMethod, req.Path, code, extra)
return res, err
}
}This library is distributed under the terms of the Apache License 2.0.
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