交通建设门户网站,ps设计教程网,快站教程,旅行社网站的建设开题报告这篇文章是记录自己查看客户端grpc负载均衡源码的过程#xff0c;并没有太详细的讲解#xff0c;参考价值不大#xff0c;可以直接跳过#xff0c;主要给自己看的。一.主要接口#xff1a;Balancer Resolver1.Balancer定义Resolver定义具体位置为1.grpc源码对解析器(resol…这篇文章是记录自己查看客户端grpc负载均衡源码的过程并没有太详细的讲解参考价值不大可以直接跳过主要给自己看的。一.主要接口Balancer Resolver1.Balancer定义Resolver定义具体位置为1.grpc源码对解析器(resolver)Builder接口有三个结构体进行实现:dns,passthrough,unix。在clientconn.go文件中通过引用包在相应包的初始化方法中进行了注册2.进入internal/resolver/passthrough/passthrough.go文件中init初始化函数中看到了将passthroughBuilder进行了注册。调用了resolver包的Register函数func init() {resolver.Register(passthroughBuilder{})
}3.Register将注册后的结构保存在全局变量m中是一个map。key为Schemevalue为Builder接口。我们看到grpc默认的scheme是passthrough即透传什么也不做package resolverimport (contextnetnet/urlstringsgoogle.golang.org/grpc/attributesgoogle.golang.org/grpc/credentialsgoogle.golang.org/grpc/internal/prettygoogle.golang.org/grpc/serviceconfig
)var (// m is a map from scheme to resolver builder.m make(map[string]Builder)// defaultScheme is the default scheme to use.defaultScheme passthrough
)// TODO(bar) install dns resolver in init(){}.// Register registers the resolver builder to the resolver map. b.Scheme will be
// used as the scheme registered with this builder.
//
// NOTE: this function must only be called during initialization time (i.e. in
// an init() function), and is not thread-safe. If multiple Resolvers are
// registered with the same name, the one registered last will take effect.
func Register(b Builder) {m[b.Scheme()] b
}// Get returns the resolver builder registered with the given scheme.
//
// If no builder is register with the scheme, nil will be returned.
func Get(scheme string) Builder {if b, ok : m[scheme]; ok {return b}return nil
}4.再看下passthroughBuilder看到它实现了Buider接口Build方法返回实现Resolver接口的结构passthroughResolver。其中passthroughBuilder用来创建解析器passthroughResolver为创建的解析器package passthroughimport (errorsgoogle.golang.org/grpc/resolver
)const scheme passthroughtype passthroughBuilder struct{}func (*passthroughBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {if target.Endpoint() opts.Dialer nil {return nil, errors.New(passthrough: received empty target in Build())}r : passthroughResolver{target: target,cc: cc,}r.start()return r, nil
}func (*passthroughBuilder) Scheme() string {return scheme
}type passthroughResolver struct {target resolver.Targetcc resolver.ClientConn
}func (r *passthroughResolver) start() {r.cc.UpdateState(resolver.State{Addresses: []resolver.Address{{Addr: r.target.Endpoint()}}})
}func (*passthroughResolver) ResolveNow(o resolver.ResolveNowOptions) {}func (*passthroughResolver) Close() {}func init() {resolver.Register(passthroughBuilder{})
}5.这段代码中返回的resolverBuilder就是从上面找到注册的builderresolver.Get就是1.3中对应的代码7.生成解析器的封装newCCResolverWrapper并调用build将创建解析器这个过程中调用了解析器的start方法这个方法比较重要的是做了两件事情。1.触发选择balancer信号。2.触发状态修改其中有负载均衡即连接的创建上面分别向ccBalancerWrapper的channel中发送了switchToUpdate和ccStateUpdatebalancer选择逻辑baseBalancer会将所有地址都创建一个连接invoke的时候会调用picker选择连接以上路径最终调用这个方法可以看到是轮询使用连接
