yarpc

README

yarpc-go

With hundreds to thousands of services communicating with RPC, transport protocols (like HTTP and TChannel), encoding protocols (like JSON or Thrift), and peer choosers are the concepts that vary year over year. Separating these concerns allows services to change transports and wire protocols without changing call sites or request handlers, build proxies and wire protocol bridges, or experiment with load balancing strategies. YARPC is a toolkit for services and proxies.

YARPC breaks RPC into interchangeable encodings, transports, and peer choosers. YARPC for Go provides reference implementations for HTTP/1.1 and TChannel transports, and also raw, JSON, and Thrift encodings. YARPC for Go provides experimental implementations for a Redis transport and a round robin peer chooser. YARPC for Go plans to provide a Protobuf 3 encoding, a gRPC transport, and a load balancer that uses a least-pending-requests strategy. Peer choosers can implement any strategy, including load balancing or sharding, in turn backed by a pluggable peer provider.

Regardless of transport, every RPC has some common properties: caller name, service name, procedure name, encoding name, deadline or TTL, headers, baggage (multi-hop headers), and tracing. Each RPC can also have an optional shard key, routing key, or routing delegate for advanced routing. YARPC transports use a shared API for capturing RPC metadata, so middleware can apply to requests over any transport.

Each YARPC transport protocol can implement inbound handlers and outbound callers. Each of these can support different RPC types, like unary (request and response) or oneway (request and receipt) RPC. A future release of YARPC will add support for other RPC types including variations on streaming and pubsub.

Installation

go get -u go.uber.org/yarpc

If using Glide, at least glide version 0.12.3 is required to install:

$ glide --version
glide version 0.12.3

$ glide get 'go.uber.org/yarpc#^1'

To use Thrift code generation, you will need to install plugins. These cannot be vendored since go depends on the binaries being available on the path.

$ go get 'go.uber.org/thriftrw'
$ go get 'go.uber.org/yarpc/encoding/thrift/thriftrw-plugin-yarpc'

Examples

This example illustrates a simple service that implements a handler for a Hello::echo Thrift procedure.

service Hello {
    EchoResponse echo(1:EchoRequest echo)
}

struct EchoRequest {
    1: required string message;
    2: required i16 count;
}

struct EchoResponse {
    1: required string message;
    2: required i16 count;
}

A go:generate directive informs go generate how to produce the Thrift models and YARPC bindings for the echo service.

//go:generate thriftrw --plugin=yarpc echo.thrift

$ go generate echo.thrift

Setting up a YARPC dispatcher configures inbounds and outbounds for supported transport protocols and RPC types. This sets a service up to receive HTTP requests on port 8080 and send requests to itself. YARPC funnels requests from all inbound transports into its routing table, and organizes outbounds by name.

httpTransport := http.NewTransport()
dispatcher := yarpc.NewDispatcher(yarpc.Config{
    Name: "hello",
    Inbounds: yarpc.Inbounds{
        httpTransport.NewInbound(":8080"),
    },
    Outbounds: yarpc.Outbounds{
        "hello": {
            Unary: httpTransport.NewSingleOutbound("http://127.0.0.1:8080"),
        },
    },
})

The dispatcher governs the lifecycle of every inbound, outbound, and the singleton for each transport protocol. The singleton can manage the lifecycle of shared peers and connections.

if err := dispatcher.Start(); err != nil {
    log.Fatal(err)
}
defer dispatcher.Stop()

At the end of main, we block until we receive a signal to exit, then unravel anything deferred like dispatcher.Stop(), shutting down gracefully.

signals := make(chan os.Signal, 1)
signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)
<-signals

Handle

To receive requests from any inbound, we register a handler object using the Thrift generated server.

dispatcher.Register(helloserver.New(&helloHandler{}))

The handler must implement the Hello service from the Thrift IDL. The generated code requires a handler that implements helloserver.Interface.

type helloHandler struct{}

func (h *helloHandler) Echo(ctx context.Context, e *echo.EchoRequest) (*echo.EchoResponse, error) {
	return &echo.EchoResponse{Message: e.Message, Count: e.Count + 1}, nil
}

Call

To send a request on an outbound, we construct a client using the corresponding named outbound from the dispatcher. The client will use that name for the outbound request service name.

client := helloclient.New(dispatcher.ClientConfig("hello"))

To call a remote procedure, the context must have a deadline. We create a context with a one second deadline and call a method of the client. The client will use the dispatcher name for the caller name, Thrift for the encoding, and infer the procedure names from the Echo method (Hello::echo).

ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()

res, err := client.Echo(ctx, &echo.EchoRequest{Message: "Hello world", Count: 1})
if err != nil {
    log.Fatal(err)
}
fmt.Println(res)

Other Examples

YARPC also provides examples for the oneway RPC type and a key value service using both the Thrift and JSON encodings.

Development Status: Stable

Ready for most users. No breaking changes to stable APIs will be made before 2.0.

Stable:

• handler and call sites for unary and oneway
• dispatcher constructor and config type
• transport constructors (including the tchannel.NewTransportChannel(...) although YARPC will eventually also have tchannel.NewTransport(chooser, ...))
• interfaces for "go.uber.org/yarpc/api/transport" Transport (for lifecycle management), Inbound, Outbound, Request, Response, ResponseWriter, Router, RouteTable, Procedure, and Lifecycle
• interfaces for "go.uber.org/yarpc/api/peer" Transport (for peer management), Chooser, List
• the middleware API
• wire representation of RPC for HTTP and TChannel, including all required headers: Rpc-Caller, Rpc-Service, Rpc-Procedure, and Context-TTL-MS.

Unstable:

• Any package in an x directory, including the experimental Redis transport and the round-robin peer chooser.
• debug and introspection APIs (these are internal to prevent external implementations of transports, inbounds, and outbounds from making use of them, but we further do not guarantee the content of debug pages)

Upcoming:

• peer choosers for TChannel
• handle-or-forward request handlers, possibly using per-procedure middleware
• streaming RPC type for some transports (gRPC, WebSocket)
• pubsub RPC type for some transports (Redis)

Documentation

Overview

Package yarpc provides the YARPC service framework.

With hundreds to thousands of services communicating with RPC, transport protocols (like HTTP and TChannel), encoding protocols (like JSON or Thrift), and peer choosers are the concepts that vary year over year. Separating these concerns allows services to change transports and wire protocols without changing call sites or request handlers, build proxies and wire protocol bridges, or experiment with load balancing strategies. YARPC is a toolkit for services and proxies.

YARPC breaks RPC into interchangeable encodings, transports, and peer choosers. YARPC for Go provides reference implementations for HTTP/1.1 and TChannel transports, and also raw, JSON, and Thrift encodings. YARPC for Go provides experimental implementations for a Redis transport and a round robin peer chooser. YARPC for Go plans to provide a Protobuf 3 encoding, a gRPC transport, and a load balancer that uses a least-pending-requests strategy. Peer choosers can implement any strategy, including load balancing or sharding, in turn backed by a pluggable peer provider.

Regardless of transport, every RPC has some common properties: caller name, service name, procedure name, encoding name, deadline or TTL, headers, baggage (multi-hop headers), and tracing. Each RPC can also have an optional shard key, routing key, or routing delegate for advanced routing. YARPC transports use a shared API for capturing RPC metadata, so middleware can apply to requests over any transport.

Each YARPC transport protocol can implement inbound handlers and outbound callers. Each of these can support different RPC types, like unary (request and response) or oneway (request and receipt) RPC. A future release of YARPC will add support for other RPC types including variations on streaming and pubsub.

Index

• Constants
• func CanonicalizeHeaderKey(k string) string
• func InjectClients(src transport.ClientConfigProvider, dest interface{})
• func IsBadRequestError(err error) bool
• func IsTimeoutError(err error) bool
• func IsUnexpectedError(err error) bool
• func OnewayInboundMiddleware(mw ...middleware.OnewayInbound) middleware.OnewayInbound
• func OnewayOutboundMiddleware(mw ...middleware.OnewayOutbound) middleware.OnewayOutbound
• func RegisterClientBuilder(f interface{}) (forget func())
• func UnaryInboundMiddleware(mw ...middleware.UnaryInbound) middleware.UnaryInbound
• func UnaryOutboundMiddleware(mw ...middleware.UnaryOutbound) middleware.UnaryOutbound
• type Ack
• type Call
  • func CallFromContext(ctx context.Context) *Call
  • func (c *Call) Caller() string
  • func (c *Call) Encoding() transport.Encoding
  • func (c *Call) Header(k string) string
  • func (c *Call) HeaderNames() []string
  • func (c *Call) Procedure() string
  • func (c *Call) RoutingDelegate() string
  • func (c *Call) RoutingKey() string
  • func (c *Call) Service() string
  • func (c *Call) ShardKey() string
  • func (c *Call) WriteResponseHeader(k, v string) error
• type CallOption
  • func ResponseHeaders(h *map[string]string) CallOption
  • func WithHeader(k, v string) CallOption
  • func WithRoutingDelegate(rd string) CallOption
  • func WithRoutingKey(rk string) CallOption
  • func WithShardKey(sk string) CallOption
• type Config
• type Dispatcher
  • func NewDispatcher(cfg Config) *Dispatcher
  • func (d *Dispatcher) ClientConfig(service string) transport.ClientConfig
  • func (d *Dispatcher) Inbounds() Inbounds
  • func (d *Dispatcher) Register(rs []transport.Procedure)
  • func (d *Dispatcher) Start() error
  • func (d *Dispatcher) Stop() error
• type InboundMiddleware
• type Inbounds
• type MapRouter
  • func NewMapRouter(defaultService string) MapRouter
  • func (m MapRouter) Choose(ctx context.Context, req *transport.Request) (transport.HandlerSpec, error)
  • func (m MapRouter) Procedures() []transport.Procedure
  • func (m MapRouter) Register(rs []transport.Procedure)
• type OutboundMiddleware
• type Outbounds

Examples

• Dispatcher (Minimal)
• Dispatcher.Register (JSON)
• Dispatcher.Register (Raw)

Constants

const Version = "1.0.1"

Version is the current version of YARPC.

Functions

func CanonicalizeHeaderKey

func CanonicalizeHeaderKey(k string) string

CanonicalizeHeaderKey canonicalizes the given header key to the same form used by the headers map returned by ResponseHeaders.

var headers map[string]string
res, err := client.Call(ctx, "hello", requestBody, ResponseHeaders(&headers))
email, ok := headers[CanonicalizeHeaderKey("User-Email-Address")]

func InjectClients

func InjectClients(src transport.ClientConfigProvider, dest interface{})

InjectClients injects clients from a Dispatcher into the given struct. dest must be a pointer to a struct with zero or more exported fields which hold YARPC client types. This includes json.Client, raw.Client, and any generated Thrift service client. Fields with nil values and a `service` tag will be populated with clients using that service`s ClientConfig.

Given,

type Handler struct {
	KeyValueClient keyvalueclient.Interface `service:"keyvalue"`
	UserClient json.Client `service:"users"`
	TagClient tagclient.Interface  // no tag; will be left unchanged
}

The call,

var h Handler
yarpc.InjectClients(dispatcher, &h)

Is equivalent to,

var h Handler
h.KeyValueClient = keyvalueclient.New(dispatcher.ClientConfig("keyvalue"))
h.UserClient = json.New(dispatcher.ClientConfig("users"))

Builder functions for different client types may be registered using the RegisterClientBuilder function.

This function panics if a field with an unknown type and nil value has the `service` tag.

func IsBadRequestError

func IsBadRequestError(err error) bool

IsBadRequestError returns true on an error returned by RPC clients if the request was rejected by YARPC because it was invalid.

res, err := client.Call(...)
if yarpc.IsBadRequestError(err) {
	fmt.Println("invalid request:", err)
}

func IsTimeoutError

func IsTimeoutError(err error) bool

IsTimeoutError return true on an error returned by RPC clients if the given error is a TimeoutError.

res, err := client.Call(...)
if yarpc.IsTimeoutError(err) {
	fmt.Println("request timed out:", err)
}

func IsUnexpectedError

func IsUnexpectedError(err error) bool

IsUnexpectedError returns true on an error returned by RPC clients if the server panicked or failed with an unhandled error.

res, err := client.Call(...)
if yarpc.IsUnexpectedError(err) {
	fmt.Println("internal server error:", err)
}

func OnewayInboundMiddleware

func OnewayInboundMiddleware(mw ...middleware.OnewayInbound) middleware.OnewayInbound

OnewayInboundMiddleware combines the given collection of unary inbound middleware in-order into a single OnewayInbound middleware.

func OnewayOutboundMiddleware

func OnewayOutboundMiddleware(mw ...middleware.OnewayOutbound) middleware.OnewayOutbound

OnewayOutboundMiddleware combines the given collection of unary outbound middleware in-order into a single OnewayOutbound middleware.

func RegisterClientBuilder

func RegisterClientBuilder(f interface{}) (forget func())

RegisterClientBuilder registers a builder function for a specific client type.

Functions must have the signature,

func(transport.ClientConfig) T

Where T is the type of the client. T MUST be an interface.

This function panics if a client for the given type has already been registered.

After a builder function for a client type is registered, these objects can be instantiated automatically using InjectClients.

A function to unregister the builder function is returned. Note that the function will clear whatever the corresponding type's builder function is at the time it is called, regardless of whether the value matches what was passed to this function or not.

func UnaryInboundMiddleware

func UnaryInboundMiddleware(mw ...middleware.UnaryInbound) middleware.UnaryInbound

UnaryInboundMiddleware combines the given collection of unary inbound middleware in-order into a single UnaryInbound middleware.

func UnaryOutboundMiddleware

func UnaryOutboundMiddleware(mw ...middleware.UnaryOutbound) middleware.UnaryOutbound

UnaryOutboundMiddleware combines the given collection of unary outbound middleware in-order into a single UnaryOutbound middleware.

Types

type Ack

type Ack interface {
	fmt.Stringer
}

Ack represents an acknowledgement from a oneway request.

type Call

type Call encoding.Call

Call provides information about the current request inside handlers. An instance of Call for the current request can be obtained by calling CallFromContext on the request context.

func Get(ctx context.Context, req *GetRequest) (*GetResponse, error) {
	call := yarpc.CallFromContext(ctx)
	fmt.Println("Received request from", call.Caller())
	if err := call.WriteResponseHeader("hello", "world"); err != nil {
		return nil, err
	}
	return response, nil
}

func CallFromContext

func CallFromContext(ctx context.Context) *Call

CallFromContext retrieves information about the current incoming request from the given context. Returns nil if the context is not a valid request context.

The object is valid only as long as the request is ongoing.

func (*Call) Caller

func (c *Call) Caller() string

Caller returns the name of the service making this request.

func (*Call) Encoding

func (c *Call) Encoding() transport.Encoding

Encoding returns the encoding for this request.

func (*Call) Header

func (c *Call) Header(k string) string

Header returns the value of the given request header provided with the request.

func (*Call) HeaderNames

func (c *Call) HeaderNames() []string

HeaderNames returns a sorted list of the names of user defined headers provided with this request.

func (*Call) Procedure

func (c *Call) Procedure() string

Procedure returns the name of the procedure being called.

func (*Call) RoutingDelegate

func (c *Call) RoutingDelegate() string

RoutingDelegate returns the routing delegate for this request.

func (*Call) RoutingKey

func (c *Call) RoutingKey() string

RoutingKey returns the routing key for this request.

func (*Call) Service

func (c *Call) Service() string

Service returns the name of the service being called.

func (*Call) ShardKey

func (c *Call) ShardKey() string

ShardKey returns the shard key for this request.

func (*Call) WriteResponseHeader

func (c *Call) WriteResponseHeader(k, v string) error

WriteResponseHeader writes headers to the response of this call.

type CallOption

type CallOption encoding.CallOption

CallOption defines options that may be passed in at call sites to other services.

These may be used to add or alter the request.

func ResponseHeaders

func ResponseHeaders(h *map[string]string) CallOption

ResponseHeaders specifies that headers received in response to this request should replace the given map.

Header keys in the map are normalized using the CanonicalizeHeaderKey function.

var resHeaders map[string]string
resBody, err := client.SetValue(ctx, key, value, yarpc.ResponseHeaders(&resHeaders))
value, ok := resHeaders[yarpc.CanonicalizeHeaderKey("foo")]

Note that the map is replaced completely. Entries it had before making the call will not be available afterwards.

headers := map[string]string{"hello": "world"}
resBody, err := client.SetValue(ctx, key, value, yarpc.ResponseHeaders(&headers))
_, ok := headers["hello"]
fmt.Println(ok)  // false

func WithHeader

func WithHeader(k, v string) CallOption

WithHeader adds a new header to the request. Header keys are case insensitive.

_, err := client.GetValue(ctx, reqBody, yarpc.WithHeader("Token", "10"))
// ==> {"token": "10"}

If multiple entries have the same normalized header name, newer entries override older ones.

func WithRoutingDelegate

func WithRoutingDelegate(rd string) CallOption

WithRoutingDelegate sets the routing delegate for the request.

func WithRoutingKey

func WithRoutingKey(rk string) CallOption

WithRoutingKey sets the routing key for the request.

func WithShardKey

func WithShardKey(sk string) CallOption

WithShardKey sets the shard key for the request.

type Config

type Config struct {
	// Name of the service. This is the name used by other services when
	// making requests to this service.
	Name string

	// Inbounds define how this service receives incoming requests from other
	// services.
	//
	// This may be nil if this service does not receive any requests.
	Inbounds Inbounds

	// Outbounds defines how this service makes requests to other services.
	//
	// This may be nil if this service does not send any requests.
	Outbounds Outbounds

	// Inbound and Outbound Middleware that will be applied to all incoming
	// and outgoing requests respectively.
	//
	// These may be nil if there is no middleware to apply.
	InboundMiddleware  InboundMiddleware
	OutboundMiddleware OutboundMiddleware

	// Tracer is deprecated. The dispatcher does nothing with this propery.
	Tracer opentracing.Tracer
}

Config specifies the parameters of a new Dispatcher constructed via NewDispatcher.

type Dispatcher

type Dispatcher struct {
	// contains filtered or unexported fields
}

Dispatcher encapsulates a YARPC application. It acts as the entry point to send and receive YARPC requests in a transport and encoding agnostic way.

Example (Minimal)

package main

import (
	"log"

	"go.uber.org/yarpc"
)

func main() {
	dispatcher := yarpc.NewDispatcher(yarpc.Config{Name: "myFancyService"})
	if err := dispatcher.Start(); err != nil {
		log.Fatal(err)
	}
	defer dispatcher.Stop()
}

func NewDispatcher

func NewDispatcher(cfg Config) *Dispatcher

NewDispatcher builds a new Dispatcher using the specified Config. At minimum, a service name must be specified.

Invalid configurations or errors in constructing the Dispatcher will cause panics.

func (*Dispatcher) ClientConfig

func (d *Dispatcher) ClientConfig(service string) transport.ClientConfig

ClientConfig provides the configuration needed to talk to the given service. This configuration may be directly passed into encoding-specific RPC clients.

keyvalueClient := json.New(dispatcher.ClientConfig("keyvalue"))

This function panics if the service name is not known.

func (*Dispatcher) Inbounds

func (d *Dispatcher) Inbounds() Inbounds

Inbounds returns a copy of the list of inbounds for this RPC object.

The Inbounds will be returned in the same order that was used in the configuration.

func (*Dispatcher) Register

func (d *Dispatcher) Register(rs []transport.Procedure)

Register registers zero or more procedures with this dispatcher. Incoming requests to these procedures will be routed to the handlers specified in the given Procedures.

Example (JSON)

package main

import (
	"context"
	"fmt"

	"go.uber.org/yarpc"
	"go.uber.org/yarpc/encoding/json"
)

// global dispatcher used in the registration examples
var dispatcher = yarpc.NewDispatcher(yarpc.Config{Name: "service"})

func main() {
	handler := func(ctx context.Context, key string) (string, error) {
		fmt.Println("key", key)
		return "value", nil
	}

	dispatcher.Register(json.Procedure("get", handler))
}

Example (Raw)

package main

import (
	"context"

	"go.uber.org/yarpc"
	"go.uber.org/yarpc/encoding/raw"
)

// global dispatcher used in the registration examples
var dispatcher = yarpc.NewDispatcher(yarpc.Config{Name: "service"})

func main() {
	handler := func(ctx context.Context, data []byte) ([]byte, error) {
		return data, nil
	}

	dispatcher.Register(raw.Procedure("echo", handler))
}

func (*Dispatcher) Start

func (d *Dispatcher) Start() error

Start starts the Dispatcher, allowing it to accept and processing new incoming requests.

This starts all inbounds and outbounds configured on this Dispatcher.

This function returns immediately after everything has been started. Servers should add a `select {}` to block to process all incoming requests.

if err := dispatcher.Start(); err != nil {
	log.Fatal(err)
}
defer dispatcher.Stop()

select {}

func (*Dispatcher) Stop

func (d *Dispatcher) Stop() error

Stop stops the Dispatcher.

This stops all outbounds and inbounds owned by this Dispatcher.

This function returns after everything has been stopped.

type InboundMiddleware

type InboundMiddleware struct {
	Unary  middleware.UnaryInbound
	Oneway middleware.OnewayInbound
}

InboundMiddleware contains the different types of inbound middlewares.

type Inbounds

type Inbounds []transport.Inbound

Inbounds contains a list of inbound transports. Each inbound transport specifies a source through which incoming requests are received.

type MapRouter

type MapRouter struct {
	// contains filtered or unexported fields
}

MapRouter is a Router that maintains a map of the registered procedures.

func NewMapRouter

func NewMapRouter(defaultService string) MapRouter

NewMapRouter builds a new MapRouter that uses the given name as the default service name.

func (MapRouter) Choose

func (m MapRouter) Choose(ctx context.Context, req *transport.Request) (transport.HandlerSpec, error)

Choose retrives the HandlerSpec for the service and procedure noted on the transport request, or returns an error.

func (MapRouter) Procedures

func (m MapRouter) Procedures() []transport.Procedure

Procedures returns a list procedures that have been registered so far.

func (MapRouter) Register

func (m MapRouter) Register(rs []transport.Procedure)

Register registers the procedure with the MapRouter.

type OutboundMiddleware

type OutboundMiddleware struct {
	Unary  middleware.UnaryOutbound
	Oneway middleware.OnewayOutbound
}

OutboundMiddleware contains the different types of outbound middlewares.

type Outbounds

type Outbounds map[string]transport.Outbounds

Outbounds provides access to outbounds for a remote service. Outbounds define how requests are sent from this service to the remote service.