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goa.design/goa

Package goa

v1.0.1-0...-f1b9b0e
Latest Go to latest

The highest tagged major version is v3.

Published: Apr 25, 2019 | License: MIT | Module: goa.design/goa

Overview

Package goa is a Go framework for writing microservices that promotes best practice by providing a single source of truth from which server code, client code, and documentation is derived. The code generated by goa follows the clean architecture pattern where composable modules are generated for the transport, endpoint, and business logic layers. The goa package contains middleware, plugins, and other complementary functionality that can be leveraged in tandem with the generated code to implement complete microservices in an efficient manner. By using goa for developing microservices, implementers don’t have to worry with the documentation getting out of sync from the implementation as goa takes care of generating OpenAPI specifications for HTTP based services and gRPC protocol buffer files for gRPC based services (or both if the service supports both transports). Reviewers can also be assured that the implementation follows the documentation as the code is generated from the same source.

Install goa:

go get goa.design/goa/...

Write the service design:

cd $GOPATH/src
mkdir -p calc/design
echo '
package design

import . "goa.design/goa/dsl"

var _ = API("calc", func() {
    Server("http://localhost:8080")
})

var _ = Service("calc", func() {
    Method("add", func() {
        Payload(func() {
            Field(1, "left", Int, "Left operand")
            Field(2, "right", Int, "Right operand")
        })
        Result(Int)
        HTTP(func() {
            GET("/")
        })
    })
})
' > calc/design/design.go

Generate the supporting code:

goa gen calc/design

Generate an "example" implementation:

goa example calc/design

Build server and client code:

go build ./cmd/calc && go build ./cmd/calc-cli

Visit https://goa.design for more information.

Index

Constants

const (
	// MethodKey is the request context key used to store the name of the
	// method as defined in the design. The generated transport code
	// initializes the corresponding value prior to invoking the endpoint.
	MethodKey contextKey = iota + 1

	// ServiceKey is the request context key used to store the name of the
	// service as defined in the design. The generated transport code
	// initializes the corresponding value prior to invoking the endpoint.
	ServiceKey
)
const (
	// FormatDate describes RFC3339 date values.
	FormatDate Format = "date"

	// FormatDateTime describes RFC3339 date time values.
	FormatDateTime Format = "date-time"

	// FormatUUID describes RFC4122 UUID values.
	FormatUUID = "uuid"

	// FormatEmail describes RFC5322 email addresses.
	FormatEmail = "email"

	// FormatHostname describes RFC1035 Internet hostnames.
	FormatHostname = "hostname"

	// FormatIPv4 describes RFC2373 IPv4 address values.
	FormatIPv4 = "ipv4"

	// FormatIPv6 describes RFC2373 IPv6 address values.
	FormatIPv6 = "ipv6"

	// FormatIP describes RFC2373 IPv4 or IPv6 address values.
	FormatIP = "ip"

	// FormatURI describes RFC3986 URI values.
	FormatURI = "uri"

	// FormatMAC describes IEEE 802 MAC-48, EUI-48 or EUI-64 MAC address values.
	FormatMAC = "mac"

	// FormatCIDR describes RFC4632 and RFC4291 CIDR notation IP address values.
	FormatCIDR = "cidr"

	// FormatRegexp describes regular expression syntax accepted by RE2.
	FormatRegexp = "regexp"

	// FormatJSON describes JSON text.
	FormatJSON = "json"

	// FormatRFC1123 describes RFC1123 date time values.
	FormatRFC1123 = "rfc1123"
)

func DecodePayloadError

func DecodePayloadError(msg string) error

DecodePayloadError is the error produced by the generated code when a request body cannot be decoded successfully.

func InvalidEnumValueError

func InvalidEnumValueError(name string, val interface{}, allowed []interface{}) error

InvalidEnumValueError is the error produced by the generated code when the value of a payload field does not match one the values defined in the design Enum validation.

func InvalidFieldTypeError

func InvalidFieldTypeError(name string, val interface{}, expected string) error

InvalidFieldTypeError is the error produced by the generated code when the type of a payload field does not match the type defined in the design.

func InvalidFormatError

func InvalidFormatError(name, target string, format Format, formatError error) error

InvalidFormatError is the error produced by the generated code when the value of a payload field does not match the format validation defined in the design.

func InvalidLengthError

func InvalidLengthError(name string, target interface{}, ln, value int, min bool) error

InvalidLengthError is the error produced by the generated code when the value of a payload field does not match the length validation defined in the design.

func InvalidPatternError

func InvalidPatternError(name, target string, pattern string) error

InvalidPatternError is the error produced by the generated code when the value of a payload field does not match the pattern validation defined in the design.

func InvalidRangeError

func InvalidRangeError(name string, target interface{}, value interface{}, min bool) error

InvalidRangeError is the error produced by the generated code when the value of a payload field does not match the range validation defined in the design. value may be an int or a float64.

func MergeErrors

func MergeErrors(err, other error) error

MergeErrors updates an error by merging another into it. It first converts other into a ServiceError if not already one. The merge algorithm then:

* uses the name of err if a ServiceError, the name of other otherwise.

* appends both error messages.

* computes Timeout and Temporary by "and"ing the fields of both errors.

Merge returns the updated error. This makes it possible to return other when err is nil.

func MissingFieldError

func MissingFieldError(name, context string) error

MissingFieldError is the error produced by the generated code when a payload is missing a required field.

func MissingPayloadError

func MissingPayloadError() error

MissingPayloadError is the error produced by the generated code when a request is missing a required payload.

func NewErrorID

func NewErrorID() string

NewErrorID creates a unique 8 character ID that is well suited to use as an error identifier.

func ValidateFormat

func ValidateFormat(name string, val string, f Format) error

ValidateFormat validates val against f. It returns nil if the string conforms to the format, an error otherwise. name is the name of the variable used in error messages. where in a data structure the error occurred if any. The format specification follows the json schema draft 4 validation extension. see http://json-schema.org/latest/json-schema-validation.html#anchor105 Supported formats are:

- "date": RFC3339 date value
- "date-time": RFC3339 date time value
- "email": RFC5322 email address
- "hostname": RFC1035 Internet host name
- "ipv4", "ipv6", "ip": RFC2673 and RFC2373 IP address values
- "uri": RFC3986 URI value
- "mac": IEEE 802 MAC-48, EUI-48 or EUI-64 MAC address value
- "cidr": RFC4632 and RFC4291 CIDR notation IP address value
- "regexp": Regular expression syntax accepted by RE2
- "rfc1123": RFC1123 date time value

func ValidatePattern

func ValidatePattern(name, val, p string) error

ValidatePattern returns an error if val does not match the regular expression p. It makes an effort to minimize the number of times the regular expression needs to be compiled. name is the name of the variable used in error messages.

type Endpoint

type Endpoint func(ctx context.Context, request interface{}) (response interface{}, err error)

Endpoint exposes service methods to remote clients independently of the underlying transport.

type Format

type Format string

Format defines a validation format.

type ServiceError

type ServiceError struct {
	// Name is a name for that class of errors.
	Name string
	// ID is a unique value for each occurrence of the error.
	ID string
	// Message contains the specific error details.
	Message string
	// Is the error a timeout?
	Timeout bool
	// Is the error temporary?
	Temporary bool
	// Is the error a server-side fault?
	Fault bool
}

ServiceError is the default error type used by the goa package to encode and decode error responses.

func Fault

func Fault(format string, v ...interface{}) *ServiceError

Fault creates an error given a format and values a la fmt.Printf. The error has the Fault field set to true.

func PermanentError

func PermanentError(name, format string, v ...interface{}) *ServiceError

PermanentError creates an error given a name and a format and values a la fmt.Printf.

func PermanentTimeoutError

func PermanentTimeoutError(name, format string, v ...interface{}) *ServiceError

PermanentTimeoutError creates an error given a name and a format and values a la fmt.Printf. The error has the Timeout field set to true.

func TemporaryError

func TemporaryError(name, format string, v ...interface{}) *ServiceError

TemporaryError is an error class that indicates that the error is temporary and that retrying the request may be successful. TemporaryError creates an error given a name and a format and values a la fmt.Printf. The error has the Temporary field set to true.

func TemporaryTimeoutError

func TemporaryTimeoutError(name, format string, v ...interface{}) *ServiceError

TemporaryTimeoutError creates an error given a name and a format and values a la fmt.Printf. The error has both the Timeout and Temporary fields set to true.

func (*ServiceError) Error

func (s *ServiceError) Error() string

Error returns the error message.

func (*ServiceError) ErrorName

func (s *ServiceError) ErrorName() string

ErrorName returns the error name.

Package Files

Documentation was rendered with GOOS=linux and GOARCH=amd64.

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