handler

Documentation

Overview

Package handler provides standard HTTP handlers for the WebPA servers.

Index

• Constants
• func Recover(ctx context.Context, response http.ResponseWriter)
• func WriteError(response http.ResponseWriter, err interface{}) error
• func WriteJsonError(response http.ResponseWriter, code int, message string) error
• type AuthorizationHandler
  • func (a AuthorizationHandler) Decorate(delegate http.Handler) http.Handler
• type Chain
  • func (chain Chain) Decorate(initial context.Context, contextHandler ContextHandler) http.Handler
  • func (chain Chain) Len() int
• type ChainHandler
  • func Convey() ChainHandler
  • func ConveyCustom(conveyHeader string, encoding *base64.Encoding) ChainHandler
  • func DeviceId() ChainHandler
  • func DeviceIdCustom(deviceNameHeader string) ChainHandler
  • func Listen(listeners ...RequestListener) ChainHandler
  • func RequestGate(connection Connection, unavailableStatus int, unavailableMessage string) ChainHandler
• type ChainHandlerFunc
  • func (f ChainHandlerFunc) ServeHTTP(requestContext context.Context, response http.ResponseWriter, ...)
• type Connection
  • func MergeConnections(connections ...Connection) Connection
• type ConnectionFunc
  • func (f ConnectionFunc) Connected() bool
• type ContextHandler
  • func Hash(serviceHash hash.ServiceHash) ContextHandler
  • func HashCustom(serviceHash hash.ServiceHash, redirectCode int) ContextHandler
• type ContextHandlerFunc
  • func (f ContextHandlerFunc) ServeHTTP(ctx context.Context, response http.ResponseWriter, request *http.Request)
• type HttpError
  • func NewHttpError(code int, message string) HttpError
• type RequestListener
  • func NewHealthRequestListener(sink healthEventSink) RequestListener

Examples

• Chain
• Convey
• DeviceId
• Hash

Constants

const (
	// The Content-Type value for JSON
	JsonContentType string = "application/json; charset=UTF-8"

	// The Content-Type header
	ContentTypeHeader string = "Content-Type"

	// The X-Content-Type-Options header
	ContentTypeOptionsHeader string = "X-Content-Type-Options"

	// The X-Webpa-Convey header
	ConveyHeader string = "X-Webpa-Convey"

	// DeviceNameHeader is the standard name of the header which carries the WebPA device
	DeviceNameHeader string = "X-Webpa-Device-Name"

	// MissingDeviceNameHeaderMessage is the error message indicating that the DeviceNameHeader
	// was missing from the request.
	MissingDeviceNameHeaderMessage string = "Missing " + DeviceNameHeader + " header"

	// InvalidDeviceNameHeaderPattern is the format pattern used to create an error message indicating
	// that a device name was improperly formatted.
	InvalidDeviceNameHeaderPattern string = "Invalid " + DeviceNameHeader + " header [%s]: %s"

	// InvalidConveyPattern is the format pattern used to create an error message indicating that
	// a convey payload was invalid.
	InvalidConveyPattern string = "Invalid " + ConveyHeader + " header [%s]: %v"

	// NoSniff is the value used for content options for errors written by this package
	NoSniff string = "nosniff"
)

const (
	TotalRequestsReceived            health.Stat = "TotalRequestsReceived"
	TotalRequestSuccessfullyServiced health.Stat = "TotalRequestSuccessfullyServiced"
	TotalRequestDenied               health.Stat = "TotalRequestDenied"
)

Functions

func Recover

func Recover(ctx context.Context, response http.ResponseWriter)

Recover provides panic recovery for a chain of requests. This function *must* be called as a deferred function.

func WriteError

func WriteError(response http.ResponseWriter, err interface{}) error

WriteError handles writing errors, possibly from panic, in a standard way. This method permits a variety of types for the err value.

func WriteJsonError

func WriteJsonError(response http.ResponseWriter, code int, message string) error

WriteJsonError writes a standard JSON error to the response

Types

type AuthorizationHandler

type AuthorizationHandler struct {
	HeaderName          string
	ForbiddenStatusCode int
	Validator           secure.Validator
	Logger              logging.Logger
}

AuthorizationHandler provides decoration for http.Handler instances and will ensure that requests pass the validator. Note that secure.Validators is a Validator implementation that allows chaining validators together via logical OR.

func (AuthorizationHandler) Decorate

func (a AuthorizationHandler) Decorate(delegate http.Handler) http.Handler

Decorate provides an Alice-compatible constructor that validates requests using the configuration specified.

type Chain

type Chain []ChainHandler

Chain represents an ordered slice of ChainHandlers that will be applied to each request.

Example

logger := &logging.LoggerWriter{os.Stdout}
ctx := fact.SetLogger(context.Background(), logger)

contextHandler := ContextHandlerFunc(func(ctx context.Context, response http.ResponseWriter, request *http.Request) {
	logger := fact.MustLogger(ctx)
	payloadJson, err := json.Marshal(fact.MustConvey(ctx))
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to marshal convey payload: %v\n", err)
		return
	}

	logger.Info("%s", payloadJson)
	logger.Info("%s", fact.MustDeviceId(ctx))
})

response, request := dummyHttpOperation()
request.Header.Add(ConveyHeader, "eyJuYW1lIjoidmFsdWUifQ==")
request.Header.Add(DeviceNameHeader, "mac:111122223333")

Chain{
	Convey(),
	DeviceId(),
}.Decorate(ctx, contextHandler).ServeHTTP(response, request)

Output:

[INFO]  {"name":"value"}
[INFO]  mac:111122223333

func (Chain) Decorate

func (chain Chain) Decorate(initial context.Context, contextHandler ContextHandler) http.Handler

Decorate produces a single http.Handler that executes each handler in the chain in sequence before finally executing a ContextHandler. The given Context is passed through the chain, and may be modified at each step.

func (Chain) Len

func (chain Chain) Len() int

Len returns the number of handlers in this chain

type ChainHandler

type ChainHandler interface {
	ServeHTTP(context.Context, http.ResponseWriter, *http.Request, ContextHandler)
}

ChainHandler represents an HTTP handler type that is one part of a chain of handlers.

func Convey

func Convey() ChainHandler

Example

contextHandler := ContextHandlerFunc(func(ctx context.Context, response http.ResponseWriter, request *http.Request) {
	payload := fact.MustConvey(ctx)
	payloadJson, err := json.Marshal(payload)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Could not marshal payload: %v\n", err)
	} else {
		fmt.Printf("%s\n", payloadJson)
	}
})

response, request := dummyHttpOperation()
request.Header.Add(ConveyHeader, "eyJuYW1lIjoidmFsdWUifQ==")
Convey().ServeHTTP(context.Background(), response, request, contextHandler)

Output:

{"name":"value"}

func ConveyCustom

func ConveyCustom(conveyHeader string, encoding *base64.Encoding) ChainHandler

func DeviceId

func DeviceId() ChainHandler

DeviceId parses out the DeviceNameHeader from the request

Example

logger := &logging.LoggerWriter{os.Stdout}
ctx := fact.SetLogger(context.Background(), logger)
contextHandler := ContextHandlerFunc(func(ctx context.Context, response http.ResponseWriter, request *http.Request) {
	deviceId := fact.MustDeviceId(ctx)
	fact.MustLogger(ctx).Info("%s", deviceId)
})

response, request := dummyHttpOperation()
request.Header.Add(DeviceNameHeader, "mac:111122223333")
DeviceId().ServeHTTP(ctx, response, request, contextHandler)

Output:

[INFO]  mac:111122223333

func DeviceIdCustom

func DeviceIdCustom(deviceNameHeader string) ChainHandler

DeviceIdCustom allows the header used for the device name to be customized

func Listen

func Listen(listeners ...RequestListener) ChainHandler

Listen produces a ChainHandler that notifies the given list of listeners of request events. This handler also provides panic recovery. Upon a recovered panic, this ChainHandler ensures that listener.RequestCompleted is invoked.

func RequestGate

func RequestGate(connection Connection, unavailableStatus int, unavailableMessage string) ChainHandler

RequestGate returns a ChainHandler whose requests are gated by the given RequestGate

type ChainHandlerFunc

type ChainHandlerFunc func(context.Context, http.ResponseWriter, *http.Request, ContextHandler)

ChainHandlerFunc is a function type that implements ChainHandler

func (ChainHandlerFunc) ServeHTTP

func (f ChainHandlerFunc) ServeHTTP(requestContext context.Context, response http.ResponseWriter, request *http.Request, next ContextHandler)

type Connection

type Connection interface {
	// Connected returns a boolean indicating whether the abstract system
	// denoted by this instance is available.
	Connected() bool
}

Connection represents some sort of subsystem or remote system that has a notion of being available

func MergeConnections

func MergeConnections(connections ...Connection) Connection

MergeConnections returns an aggregate Connection object that returns false if any of the given Connection objects return false.

type ConnectionFunc

type ConnectionFunc func() bool

ConnectionFunc is a function type that implements Connection

func (ConnectionFunc) Connected

func (f ConnectionFunc) Connected() bool

type ContextHandler

type ContextHandler interface {
	// ServeHTTP handles an HTTP request within an enclosing WebPA context
	ServeHTTP(context.Context, http.ResponseWriter, *http.Request)
}

ContextHandler defines the behavior of types which can handle HTTP requests inside a WebPA context

func Hash

func Hash(serviceHash hash.ServiceHash) ContextHandler

Hash returns a redirector using the default status code of http.StatusTemporaryRedirect.

Example

var output bytes.Buffer
logger := &logging.LoggerWriter{&output}
ctx := fact.SetLogger(context.Background(), logger)

deviceID, err := device.ParseID("mac:111122223333")
if err != nil {
	fmt.Fprintf(os.Stderr, "Error while parsing device id: %v\n", err)
	return
}

ctx = fact.SetDeviceId(ctx, deviceID)
serviceHash := &testServiceHash{value: "http://comcast.net"}
response, request := dummyHttpOperation()
request.URL.Path = "/foo/bar"
hash := Hash(serviceHash)

hash.ServeHTTP(ctx, response, request)

fmt.Println(response.Code)
fmt.Println(response.Header().Get("Location"))

Output:

307
http://comcast.net/foo/bar

func HashCustom

func HashCustom(serviceHash hash.ServiceHash, redirectCode int) ContextHandler

HashCustom provides a ContextHandler that redirects requests based on a ServiceHash. The context must have a device identifier, which is then used as the key supplied to the hash.

type ContextHandlerFunc

type ContextHandlerFunc func(context.Context, http.ResponseWriter, *http.Request)

ContextHandlerFunc is a function type that implements ContextHandler

func (ContextHandlerFunc) ServeHTTP

func (f ContextHandlerFunc) ServeHTTP(ctx context.Context, response http.ResponseWriter, request *http.Request)

type HttpError

type HttpError interface {
	error
	Code() int
}

HttpError extends the error interface to include error information for HTTP responses

func NewHttpError

func NewHttpError(code int, message string) HttpError

NewHttpError creates a new HttpError object. This object implements go's builtin error interface.

type RequestListener

type RequestListener interface {
	// RequestReceived is invoked anytime a handler receives a request
	RequestReceived(*http.Request)

	// RequestCompleted is invoked after the response has been written.
	// The first parameter is the response status code, e.g. http.StatusOk
	RequestCompleted(int, *http.Request)
}

RequestListener gets notified of certain high-level request events

func NewHealthRequestListener

func NewHealthRequestListener(sink healthEventSink) RequestListener

NewHealthRequestListener returns a new RequestListener which dispatches request stats