go微服务框架go-micro架构学习(源码分析)
产品嘴里的一个小项目，从立项到开发上线，随着时间和需求的不断激增，会越来越复杂，变成一个大项目，如果前期项目架构没设计的不好，代码会越来越臃肿，难以维护，后期的每次产品迭代上线都会牵一发而动全身。项目微服务化，松耦合模块间的关系，是一个很好的选择，随然增加了维护成本，但是还是很值得的。
微服务化项目除了稳定性我个人还比较关心的几个问题：
一: 服务间数据传输的效率和安全性。
二: 服务的动态扩充，也就是服务的注册和发现，服务集群化。
三: 微服务功能的可订制化，因为并不是所有的功能都会很符合你的需求，难免需要根据自己的需要二次开发一些功能。
go-micro是go语言下的一个很好的rpc微服务框架，功能很完善，而且我关心的几个问题也解决的很好：
一：服务间传输格式为protobuf，效率上没的说，非常的快，也很安全。
二：go-micro的服务注册和发现是多种多样的。我个人比较喜欢etcdv3的服务服务发现和注册。
三：主要的功能都有相应的接口，只要实现相应的接口，就可以根据自己的需要订制插件。
业余时间把go-micro的源码系统地读了一遍，越读越感觉这个框架写的好，从中也学到了很多东西。就想整理一系列的帖子，把学习go-micro的心得和大家分享。
通信流程
go-micro的通信流程大至如下:
Server监听客户端的调用，和Brocker推送过来的信息进行处理。并且Server端需要向Register注册自己的存在或消亡，这样Client才能知道自己的状态。
Register服务的注册的发现。
Client端从Register中得到Server的信息，然后每次调用都根据算法选择一个的Server进行通信，当然通信是要经过编码/解码，选择传输协议等一系列过程的。
如果有需要通知所有的Server端可以使用Brocker进行信息的推送。
Brocker 信息队列进行信息的接收和发布。
go-micro之所以可以高度订制和他的框架结构是分不开的，go-micro由8个关键的interface组成，每一个interface都可以根据自己的需求重新实现，这8个主要的inteface也构成了go-micro的框架结构。
这些接口go-micir都有他自己默认的实现方式，还有一个go-plugins是对这些接口实现的可替换项。你也可以根据需求实现自己的插件。
通过 go-plugins 可以设置其他服务发现，如mdns, etcd,etcdv3,zookeeper,kubernetes.等等。
#部分代码
import "github.com/micro/go-plugins/registry/etcdv3"
// 我这里用的etcd 做为服务发现，如果使用consul可以去掉
etcdv3.NewRegistry()
//etcd.NewRegistry()
//mdns.NewMDNSService()
//zookeeper.NewRegistry()
//kubernetes.NewRegistry()
service := micro.NewService(micro.Name("greeter"),
micro.Version("latest"),
micro.Metadata(map[string]string{"type": "hello world"}))
service.Init()
这篇帖子主要是给大家介绍go-micro的主体结构和这些接口的功能，具体细节以后的文章我们再慢慢说。
Transort
服务之间通信的接口。也就是服务发送和接收的最终实现方式，是由这些接口定制的。
源码：
// Package transport is an interface for synchronous communication
package transport
import (
"time"
)
type Message struct {
Header map[string]string
Body []byte
}
type Socket interface {
Recv(*Message) error
Send(*Message) error
Close() error
Local() string
Remote() string
}
type Client interface {
Socket
}
type Listener interface {
Addr() string
Close() error
Accept(func(Socket)) error
}
// Transport is an interface which is used for communication between
// services. It uses socket send/recv semantics and had various
// implementations {HTTP, RabbitMQ, NATS, ...}
type Transport interface {
Init(...Option) error
Options() Options
Dial(addr string, opts ...DialOption) (Client, error)
Listen(addr string, opts ...ListenOption) (Listener, error)
String() string
}
type Option func(*Options)
type DialOption func(*DialOptions)
type ListenOption func(*ListenOptions)
var (
DefaultTransport Transport = newHTTPTransport()
DefaultDialTimeout = time.Second * 5
)
func NewTransport(opts ...Option) Transport {
return newHTTPTransport(opts...)
}
Transport 的Listen方法是一般是Server端进行调用的，他监听一个端口，等待客户端调用。
Transport 的Dial就是客户端进行连接服务的方法。他返回一个Client接口，这个接口返回一个Client接口，这个Client嵌入了Socket接口，这个接口的方法就是具体发送和接收通信的信息。
http传输是go-micro默认的同步通信机制。当然还有很多其他的插件：grpc,nats,tcp,udp,rabbitmq,nats，都是目前已经实现了的方式。在go-plugins里你都可以找到。
Codec
有了传输方式，下面要解决的就是传输编码和解码问题，go-micro有很多种编码解码方式，默认的实现方式是protobuf,当然也有其他的实现方式，json、protobuf、jsonrpc、mercury等等。
// Package codec is an interface for encoding messages
package codec
import (
"io"
)
const (
Error MessageType = iota
Request
Response
Publication
)
type MessageType int
// Takes in a connection/buffer and returns a new Codec
type NewCodec func(io.ReadWriteCloser) Codec
// Codec encodes/decodes various types of messages used within go-micro.
// ReadHeader and ReadBody are called in pairs to read requests/responses
// from the connection. Close is called when finished with the
// connection. ReadBody may be called with a nil argument to force the
// body to be read and discarded.
type Codec interface {
Reader
Writer
Close() error
String() string
}
type Reader interface {
ReadHeader(*Message, MessageType) error
ReadBody(interface{}) error
}
type Writer interface {
Write(*Message, interface{}) error
}
// Marshaler is a simple encoding interface used for the broker/transport
// where headers are not supported by the underlying implementation.
type Marshaler interface {
Marshal(interface{}) ([]byte, error)
Unmarshal([]byte, interface{}) error
String() string
}
// Message represents detailed information about
// the communication, likely followed by the body.
// In the case of an error, body may be nil.
type Message struct {
Id string
Type MessageType
Target string
Method string
Endpoint string
Error string
// The values read from the socket
Header map[string]string
Body []byte
}
Codec接口的Write方法就是编码过程，两个Read是解码过程。
Registry
服务的注册和发现，目前实现的consul,mdns, etcd,etcdv3,zookeeper,kubernetes.等等，
// Package registry is an interface for service discovery
package registry
import (
"errors"
)
// The registry provides an interface for service discovery
// and an abstraction over varying implementations
// {consul, etcd, zookeeper, ...}
type Registry interface {
Init(...Option) error
Options() Options
Register(*Service, ...RegisterOption) error
Deregister(*Service) error
GetService(string) ([]*Service, error)
ListServices() ([]*Service, error)
Watch(...WatchOption) (Watcher, error)
String() string
}
type Option func(*Options)
type RegisterOption func(*RegisterOptions)
type WatchOption func(*WatchOptions)
var (
DefaultRegistry = NewRegistry()
// Not found error when GetService is called
ErrNotFound = errors.New("not found")
// Watcher stopped error when watcher is stopped
ErrWatcherStopped = errors.New("watcher stopped")
)
// Register a service node. Additionally supply options such as TTL.
func Register(s *Service, opts ...RegisterOption) error {
return DefaultRegistry.Register(s, opts...)
}
// Deregister a service node
func Deregister(s *Service) error {
return DefaultRegistry.Deregister(s)
}
// Retrieve a service. A slice is returned since we separate Name/Version.
func GetService(name string) ([]*Service, error) {
return DefaultRegistry.GetService(name)
}
// List the services. Only returns service names
func ListServices() ([]*Service, error) {
return DefaultRegistry.ListServices()
}
// Watch returns a watcher which allows you to track updates to the registry.
func Watch(opts ...WatchOption) (Watcher, error) {
return DefaultRegistry.Watch(opts...)
}
func String() string {
return DefaultRegistry.String()
}
简单来说，就是Service 进行Register，来进行注册，Client 使用watch方法进行监控，当有服务加入或者删除时这个方法会被触发，以提醒客户端更新Service信息。
Selector
以Registry为基础，Selector 是客户端级别的负载均衡，当有客户端向服务发送请求时， selector根据不同的算法从Registery中的主机列表，得到可用的Service节点，进行通信。目前实现的有循环算法和随机算法，默认的是随机算法。
// Package selector is a way to pick a list of service nodes
package selector
import (
"errors"
"github.com/micro/go-micro/registry"
)
// Selector builds on the registry as a mechanism to pick nodes
// and mark their status. This allows host pools and other things
// to be built using various algorithms.
type Selector interface {
Init(opts ...Option) error
Options() Options
// Select returns a function which should return the next node
Select(service string, opts ...SelectOption) (Next, error)
// Mark sets the success/error against a node
Mark(service string, node *registry.Node, err error)
// Reset returns state back to zero for a service
Reset(service string)
// Close renders the selector unusable
Close() error
// Name of the selector
String() string
}
// Next is a function that returns the next node
// based on the selector's strategy
type Next func() (*registry.Node, error)
// Filter is used to filter a service during the selection process
type Filter func([]*registry.Service) []*registry.Service
// Strategy is a selection strategy e.g random, round robin
type Strategy func([]*registry.Service) Next
var (
DefaultSelector = NewSelector()
ErrNotFound = errors.New("not found")
ErrNoneAvailable = errors.New("none available")
)
默认的是实现是本地缓存，当前实现的有blacklist,label,named等方式。
Broker
Broker是消息发布和订阅的接口。很简单的一个例子，因为服务的节点是不固定的，如果有需要修改所有服务行为的需求，可以使服务订阅某个主题，当有信息发布时，所有的监听服务都会收到信息，根据你的需要做相应的行为。
// Package broker is an interface used for asynchronous messaging
package broker
// Broker is an interface used for asynchronous messaging.
type Broker interface {
Options() Options
Address() string
Connect() error
Disconnect() error
Init(...Option) error
Publish(string, *Message, ...PublishOption) error
Subscribe(string, Handler, ...SubscribeOption) (Subscriber, error)
String() string
}
// Handler is used to process messages via a subscription of a topic.
// The handler is passed a publication interface which contains the
// message and optional Ack method to acknowledge receipt of the message.
type Handler func(Publication) error
type Message struct {
Header map[string]string
Body []byte
}
// Publication is given to a subscription handler for processing
type Publication interface {
Topic() string
Message() *Message
Ack() error
}
// Subscriber is a convenience return type for the Subscribe method
type Subscriber interface {
Options() SubscribeOptions
Topic() string
Unsubscribe() error
}
var (
DefaultBroker Broker = newHttpBroker()
)
func NewBroker(opts ...Option) Broker {
return newHttpBroker(opts...)
}
func Init(opts ...Option) error {
return DefaultBroker.Init(opts...)
}
func Connect() error {
return DefaultBroker.Connect()
}
func Disconnect() error {
return DefaultBroker.Disconnect()
}
func Publish(topic string, msg *Message, opts ...PublishOption) error {
return DefaultBroker.Publish(topic, msg, opts...)
}
func Subscribe(topic string, handler Handler, opts ...SubscribeOption) (Subscriber, error) {
return DefaultBroker.Subscribe(topic, handler, opts...)
}
func String() string {
return DefaultBroker.String()
}
Broker默认的实现方式是http方式，但是这种方式不要在生产环境用。go-plugins里有很多成熟的消息队列实现方式，有kafka、nsq、rabbitmq、redis，等等。
Client
Client是请求服务的接口，他封装Transport和Codec进行rpc调用，也封装了Brocker进行信息的发布。
// Package client is an interface for an RPC client
package client
import (
"context"
"time"
"github.com/micro/go-micro/codec"
)
// Client is the interface used to make requests to services.
// It supports Request/Response via Transport and Publishing via the Broker.
// It also supports bidiectional streaming of requests.
type Client interface {
Init(...Option) error
Options() Options
NewMessage(topic string, msg interface{}, opts ...MessageOption) Message
NewRequest(service, endpoint string, req interface{}, reqOpts ...RequestOption) Request
Call(ctx context.Context, req Request, rsp interface{}, opts ...CallOption) error
Stream(ctx context.Context, req Request, opts ...CallOption) (Stream, error)
Publish(ctx context.Context, msg Message, opts ...PublishOption) error
String() string
}
// Router manages request routing
type Router interface {
SendRequest(context.Context, Request) (Response, error)
}
// Message is the interface for publishing asynchronously
type Message interface {
Topic() string
Payload() interface{}
ContentType() string
}
// Request is the interface for a synchronous request used by Call or Stream
type Request interface {
// The service to call
Service() string
// The action to take
Method() string
// The endpoint to invoke
Endpoint() string
// The content type
ContentType() string
// The unencoded request body
Body() interface{}
// Write to the encoded request writer. This is nil before a call is made
Codec() codec.Writer
// indicates whether the request will be a streaming one rather than unary
Stream() bool
}
// Response is the response received from a service
type Response interface {
// Read the response
Codec() codec.Reader
// read the header
Header() map[string]string
// Read the undecoded response
Read() ([]byte, error)
}
// Stream is the inteface for a bidirectional synchronous stream
type Stream interface {
// Context for the stream
Context() context.Context
// The request made
Request() Request
// The response read
Response() Response
// Send will encode and send a request
Send(interface{}) error
// Recv will decode and read a response
Recv(interface{}) error
// Error returns the stream error
Error() error
// Close closes the stream
Close() error
}
// Option used by the Client
type Option func(*Options)
// CallOption used by Call or Stream
type CallOption func(*CallOptions)
// PublishOption used by Publish
type PublishOption func(*PublishOptions)
// MessageOption used by NewMessage
type MessageOption func(*MessageOptions)
// RequestOption used by NewRequest
type RequestOption func(*RequestOptions)
var (
// DefaultClient is a default client to use out of the box
DefaultClient Client = newRpcClient()
// DefaultBackoff is the default backoff function for retries
DefaultBackoff = exponentialBackoff
// DefaultRetry is the default check-for-retry function for retries
DefaultRetry = RetryOnError
// DefaultRetries is the default number of times a request is tried
DefaultRetries = 1
// DefaultRequestTimeout is the default request timeout
DefaultRequestTimeout = time.Second * 5
// DefaultPoolSize sets the connection pool size
DefaultPoolSize = 100
// DefaultPoolTTL sets the connection pool ttl
DefaultPoolTTL = time.Minute
)
// Makes a synchronous call to a service using the default client
func Call(ctx context.Context, request Request, response interface{}, opts ...CallOption) error {
return DefaultClient.Call(ctx, request, response, opts...)
}
// Publishes a publication using the default client. Using the underlying broker
// set within the options.
func Publish(ctx context.Context, msg Message, opts ...PublishOption) error {
return DefaultClient.Publish(ctx, msg, opts...)
}
// Creates a new message using the default client
func NewMessage(topic string, payload interface{}, opts ...MessageOption) Message {
return DefaultClient.NewMessage(topic, payload, opts...)
}
// Creates a new client with the options passed in
func NewClient(opt ...Option) Client {
return newRpcClient(opt...)
}
// Creates a new request using the default client. Content Type will
// be set to the default within options and use the appropriate codec
func NewRequest(service, endpoint string, request interface{}, reqOpts ...RequestOption) Request {
return DefaultClient.NewRequest(service, endpoint, request, reqOpts...)
}
// Creates a streaming connection with a service and returns responses on the
// channel passed in. It's up to the user to close the streamer.
func NewStream(ctx context.Context, request Request, opts ...CallOption) (Stream, error) {
return DefaultClient.Stream(ctx, request, opts...)
}
func String() string {
return DefaultClient.String()
}
当然他也支持双工通信 Stream 这些具体的实现方式和使用方式，以后会详细解说。
默认的是rpc实现方式，他还有grpc和http方式，在go-plugins里可以找到
Server
Server看名字大家也知道是做什么的了。监听等待rpc请求。监听broker的订阅信息，等待信息队列的推送等。
// Package server is an interface for a micro server
package server
import (
"context"
"os"
"os/signal"
"syscall"
"github.com/google/uuid"
"github.com/micro/go-log"
"github.com/micro/go-micro/codec"
"github.com/micro/go-micro/registry"
)
// Server is a simple micro server abstraction
type Server interface {
Options() Options
Init(...Option) error
Handle(Handler) error
NewHandler(interface{}, ...HandlerOption) Handler
NewSubscriber(string, interface{}, ...SubscriberOption) Subscriber
Subscribe(Subscriber) error
Start() error
Stop() error
String() string
}
// Router handle serving messages
type Router interface {
// ServeRequest processes a request to completion
ServeRequest(context.Context, Request, Response) error
}
// Message is an async message interface
type Message interface {
Topic() string
Payload() interface{}
ContentType() string
}
// Request is a synchronous request interface
type Request interface {
// Service name requested
Service() string
// The action requested
Method() string
// Endpoint name requested
Endpoint() string
// Content type provided
ContentType() string
// Header of the request
Header() map[string]string
// Body is the initial decoded value
Body() interface{}
// Read the undecoded request body
Read() ([]byte, error)
// The encoded message stream
Codec() codec.Reader
// Indicates whether its a stream
Stream() bool
}
// Response is the response writer for unencoded messages
type Response interface {
// Encoded writer
Codec() codec.Writer
// Write the header
WriteHeader(map[string]string)
// write a response directly to the client
Write([]byte) error
}
// Stream represents a stream established with a client.
// A stream can be bidirectional which is indicated by the request.
// The last error will be left in Error().
// EOF indicates end of the stream.
type Stream interface {
Context() context.Context
Request() Request
Send(interface{}) error
Recv(interface{}) error
Error() error
Close() error
}
// Handler interface represents a request handler. It's generated
// by passing any type of public concrete object with endpoints into server.NewHandler.
// Most will pass in a struct.
//
// Example:
//
// type Greeter struct {}
//
// func (g *Greeter) Hello(context, request, response) error {
// return nil
// }
//
type Handler interface {
Name() string
Handler() interface{}
Endpoints() []*registry.Endpoint
Options() HandlerOptions
}
// Subscriber interface represents a subscription to a given topic using
// a specific subscriber function or object with endpoints.
type Subscriber interface {
Topic() string
Subscriber() interface{}
Endpoints() []*registry.Endpoint
Options() SubscriberOptions
}
type Option func(*Options)
var (
DefaultAddress = ":0"
DefaultName = "server"
DefaultVersion = "latest"
DefaultId = uuid.New().String()
DefaultServer Server = newRpcServer()
DefaultRouter = newRpcRouter()
)
// DefaultOptions returns config options for the default service
func DefaultOptions() Options {
return DefaultServer.Options()
}
// Init initialises the default server with options passed in
func Init(opt ...Option) {
if DefaultServer == nil {
DefaultServer = newRpcServer(opt...)
}
DefaultServer.Init(opt...)
}
// NewServer returns a new server with options passed in
func NewServer(opt ...Option) Server {
return newRpcServer(opt...)
}
// NewSubscriber creates a new subscriber interface with the given topic
// and handler using the default server
func NewSubscriber(topic string, h interface{}, opts ...SubscriberOption) Subscriber {
return DefaultServer.NewSubscriber(topic, h, opts...)
}
// NewHandler creates a new handler interface using the default server
// Handlers are required to be a public object with public
// endpoints. Call to a service endpoint such as Foo.Bar expects
// the type:
//
// type Foo struct {}
// func (f *Foo) Bar(ctx, req, rsp) error {
// return nil
// }
//
func NewHandler(h interface{}, opts ...HandlerOption) Handler {
return DefaultServer.NewHandler(h, opts...)
}
// Handle registers a handler interface with the default server to
// handle inbound requests
func Handle(h Handler) error {
return DefaultServer.Handle(h)
}
// Subscribe registers a subscriber interface with the default server
// which subscribes to specified topic with the broker
func Subscribe(s Subscriber) error {
return DefaultServer.Subscribe(s)
}
// Run starts the default server and waits for a kill
// signal before exiting. Also registers/deregisters the server
func Run() error {
if err := Start(); err != nil {
return err
}
ch := make(chan os.Signal, 1)
signal.Notify(ch, syscall.SIGTERM, syscall.SIGINT, syscall.SIGKILL)
log.Logf("Received signal %s", <-ch)
return Stop()
}
// Start starts the default server
func Start() error {
config := DefaultServer.Options()
log.Logf("Starting server %s id %s", config.Name, config.Id)
return DefaultServer.Start()
}
// Stop stops the default server
func Stop() error {
log.Logf("Stopping server")
return DefaultServer.Stop()
}
// String returns name of Server implementation
func String() string {
return DefaultServer.String()
}
参考链接：https://yq.aliyun.com/articles/633797