lamb

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!"}
}