License Build Status Coverage Status Go Report Card GoDoc Awesome Release

GoWrap is a command line tool that generates decorators for Go interface types using simple templates. With GoWrap you can easily add metrics, tracing, fallbacks, pools, and many other features into your existing code in a few seconds.




go get -u

Usage of gowrap

Usage: gowrap gen -p package -i interfaceName -t template -o output_file.go
  -g	don't put //go:generate instruction into the generated code
  -i string
    	the source interface name, i.e. "Reader"
  -o string
    	the output file name
  -p string
    	the source package import path, i.e. "io", "" or
    	a relative import path like "./generator"
  -t template
    	the template to use, it can be an HTTPS URL a local file or a
    	reference to one of the templates in the gowrap repository
  -v value
    	a key-value pair to parametrize the template,
    	arguments without an equal sign are treated as a bool values,
    	i.e. -v DecoratorName=MyDecorator -v disableChecks

This will generate an implementation of the io.Reader interface wrapped with prometheus metrics

  $ gowrap gen -p io -i Reader -t prometheus -o reader_with_metrics.go

This will generate a fallback decorator for the Connector interface that can be found in the ./connector subpackage:

  $ gowrap gen -p ./connector -i Connector -t fallback -o ./connector/with_metrics.go

Run gowrap help for more options

Hosted templates

When you specify a template with the "-t" flag, gowrap will first search for and use the local file with this name. If the file is not found, gowrap will look for the template here and use it if found.

List of available templates:

  • circuitbreaker stops executing methods of the wrapped interface after the specified number of consecutive errors and resumes execution after the specified delay
  • fallback takes several implementations of the source interface and concurrently runs each implementation if the previous attempt didn't return the result in a specified period of time, it returns the first non-error result
  • log instruments the source interface with logging using standard logger from the "log" package
  • logrus instruments the source interface with logging using popular sirupsen/logrus logger
  • opentracing instruments the source interface with opentracing spans
  • prometheus instruments the source interface with prometheus metrics
  • ratelimit instruments the source interface with RPS limit and concurrent calls limit
  • retry instruments the source interface with retries
  • robinpool puts several implementations of the source interface to the slice and for every method call it picks one implementation from the slice using the Round-robin algorithm
  • syncpool puts several implementations of the source interface to the sync.Pool and for every method call it gets one implementation from the pool and puts it back once finished
  • timeout instruments each method that accepts context with configurable timeout
  • validate runs func Validate() error method on each argument if it's present
  • twirp_error inject request data into twirp.Error as metadata
  • twirp_validate runs func Validate() error method on each argument if it's present and wraps returned error with twirp.Malformed error
  • grpc_validate runs func Validate() error method on each argument if it's present and returns InvalidArgument error in case when validation failed

By default GoWrap places the //go:generate instruction into the generated code. This allows you to regenerate decorators' code just by typing go generate ./... when you change the source interface type declaration. However if you used a remote template, the //go:generate instruction will contain the HTTPS URL of the template and therefore you will need to have internet connection in order to regenerate decorators. In order to avoid this, you can copy templates from the GoWrap repository to local files and add them to your version control system:

$ gowrap template copy fallback templates/fallback

The above command will fetch the fallback template and copy it to the templates/fallback local file. After template is copied, you can generate decorators using this local template:

$ gowrap gen -p io -i Reader -t templates/fallback reader_with_fallback.go

Custom templates

You can always write your own template that will provide the desired functionality to your interfaces. If you think that your template might be useful to others, please consider adding it to our template repository.

The structure of information passed to templates is documented with the TemplateInputs struct.




This section is empty.


This section is empty.


func RegisterCommand

func RegisterCommand(name string, cmd Command)

    RegisterCommand adds command to the global Commands map

    func Usage

    func Usage(w io.Writer) error

      Usage writes gowrap usage message to w


      type BaseCommand

      type BaseCommand struct {
      	Flags *flag.FlagSet
      	Short string
      	Usage string
      	Help  string

        BaseCommand implements Command interface

        func (BaseCommand) FlagSet

        func (b BaseCommand) FlagSet() *flag.FlagSet

          FlagSet implements Command

          func (BaseCommand) HelpMessage

          func (b BaseCommand) HelpMessage(w io.Writer) error

            HelpMessage implements Command

            func (BaseCommand) ShortDescription

            func (b BaseCommand) ShortDescription() string

              ShortDescription implements Command

              func (BaseCommand) UsageLine

              func (b BaseCommand) UsageLine() string

                UsageLine implements Command

                type Command

                type Command interface {
                	//FlagSet returns command specific flag set. If command doesn't have any flags nil should be returned.
                	FlagSet() *flag.FlagSet
                	//Run runs command
                	Run(args []string, stdout io.Writer) error
                	//Description returns short description of a command that is shown in the help message
                	ShortDescription() string
                	UsageLine() string
                	HelpMessage(w io.Writer) error

                  Command interface represents gowrap subcommand

                  func GetCommand

                  func GetCommand(name string) Command

                    GetCommand returns command from the global Commands map

                    type CommandLineError

                    type CommandLineError string

                      CommandLineError is returned from the commands when invalid command line parameters are passed

                      func (CommandLineError) Error

                      func (e CommandLineError) Error() string

                      type GenerateCommand

                      type GenerateCommand struct {
                      	// contains filtered or unexported fields

                        GenerateCommand implements Command interface

                        func NewGenerateCommand

                        func NewGenerateCommand(l remoteTemplateLoader) *GenerateCommand

                          NewGenerateCommand creates GenerateCommand

                          func (*GenerateCommand) Run

                          func (gc *GenerateCommand) Run(args []string, stdout io.Writer) error

                            Run implements Command interface

                            type TemplateCommand

                            type TemplateCommand struct {
                            	// contains filtered or unexported fields

                              TemplateCommand implements Command interface

                              func NewTemplateCommand

                              func NewTemplateCommand(loader remoteTemplateLoader) *TemplateCommand

                                NewTemplateCommand creates TemplateCommand

                                func (*TemplateCommand) Run

                                func (gc *TemplateCommand) Run(args []string, w io.Writer) error

                                  Run implements Command interface


                                  Path Synopsis