lamb

Provides the following utilities to simplify working with AWS lambda.

Handlers for API Gateway, S3 and DynamoDB
HTTP request parsing with JSON support and request body validation
HTTP response writer with JSON support
Custom error type with JSON support
Logging using zerolog
Logs with stacktrace

Request body parsing

Use the bind method to unmarshal the response body to a struct

type requestBody struct {
	Name   string `json:"name"`
}

handler := lamb.Handle(func(c *lamb.Context) error {
	var b requestBody
	err := c.Bind(&b)

	...
})

Request body validation

Implement the Validate method on the struct

type requestBody struct {
	Name   string `json:"name"`
	Status string `json:"status"`
}

func (b requestBody) Validate() error {
	if b.Status == "" {
		return errors.New("status empty")
	}
	return nil
}

handler := lamb.Handle(func(c *lamb.Context) error {
	var b requestBody
	err := c.Bind(&b)
	
	// work with requestBody.Name or err == "status empty"
	
	return c.JSON(http.StatusOK, responseBody)
}

Response writer

There are several methods provided to simplify writing HTTP responses.

handler := lamb.Handle(func(c *lamb.Context) error {
	...
	return c.JSON(http.StatusOK, responseBody)
})

lamb.OK(responseBody) sets the HTTP status code to http.StatusOK and marshals responseBody as JSON.

Errors

Custom Errors

You can pass custom lamb errors and also map then to HTTP status codes

handler := lamb.Handle(func(c *lamb.Context) error {
	return c.Error(lamb.Err{
		Status: http.StatusBadRequest,
		Code:   "INVALID_QUERY_PARAM",
		Detail: "Invalid query param",
		Params: map[string]string{
			"custom": "content",
		},
	})
})

Writes the the following response

{
  "code": "INVALID_QUERY_PARAM",
  "detail": "Invalid query param",
  "params": {
    "custom": "content"
  }
}

where params is type interface{} to support arbitrary data in responses.

Bubbling errors up

Go errors returned in the handler are automatically marshalled to a generic json HTTP response and the status code is set to 500. These errors are also logged. If you wrap the source error with eris a stack trace is included in the log.

Access the logger

func(c *lamb.Context) error {
    c.Logger.Log().Str("my_custom_field", "33").Msg("It worked!") // {"my_custom_field":"33","time":"2020-01-08T09:27:07Z","caller":"/path/to/file.go:125","message":"It worked!"}
}

# README