Add the notion of a node selector for routing
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@ -8,10 +8,18 @@ import (
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"github.com/micro/go-micro/registry"
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"github.com/micro/go-micro/registry"
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)
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)
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// NodeSelector is used to retrieve a node to which a request
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// should be routed. It takes a list of services and selects
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// a single node. If a node cannot be selected it should return
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// an error. A list of services is provided as a service may
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// have 1 or more versions.
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type NodeSelector func(service []*registry.Service) (*registry.Node, error)
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func init() {
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func init() {
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rand.Seed(time.Now().UnixNano())
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rand.Seed(time.Now().UnixNano())
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}
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}
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// Built in random hashed node selector
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func nodeSelector(service []*registry.Service) (*registry.Node, error) {
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func nodeSelector(service []*registry.Service) (*registry.Node, error) {
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if len(service) == 0 {
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if len(service) == 0 {
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return nil, errors.NotFound("go.micro.client", "Service not found")
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return nil, errors.NotFound("go.micro.client", "Service not found")
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@ -14,6 +14,7 @@ type options struct {
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registry registry.Registry
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registry registry.Registry
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transport transport.Transport
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transport transport.Transport
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wrappers []Wrapper
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wrappers []Wrapper
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selector NodeSelector
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}
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}
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// Broker to be used for pub/sub
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// Broker to be used for pub/sub
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@ -51,6 +52,13 @@ func Transport(t transport.Transport) Option {
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}
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}
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}
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}
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// Selector is used to select a node to route a request to
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func Selector(s NodeSelector) Option {
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return func(o *options) {
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o.selector = s
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}
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}
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// Adds a Wrapper to a list of options passed into the client
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// Adds a Wrapper to a list of options passed into the client
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func Wrap(w Wrapper) Option {
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func Wrap(w Wrapper) Option {
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return func(o *options) {
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return func(o *options) {
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@ -43,6 +43,10 @@ func newRpcClient(opt ...Option) Client {
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opts.broker = broker.DefaultBroker
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opts.broker = broker.DefaultBroker
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}
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}
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if opts.selector == nil {
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opts.selector = nodeSelector
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}
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rc := &rpcClient{
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rc := &rpcClient{
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once: once,
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once: once,
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opts: opts,
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opts: opts,
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@ -146,7 +150,7 @@ func (r *rpcClient) Call(ctx context.Context, request Request, response interfac
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return errors.InternalServerError("go.micro.client", err.Error())
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return errors.InternalServerError("go.micro.client", err.Error())
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}
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}
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node, err := nodeSelector(service)
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node, err := r.opts.selector(service)
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if err != nil {
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if err != nil {
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return err
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return err
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}
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}
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@ -169,7 +173,7 @@ func (r *rpcClient) Stream(ctx context.Context, request Request, responseChan in
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return nil, errors.InternalServerError("go.micro.client", err.Error())
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return nil, errors.InternalServerError("go.micro.client", err.Error())
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}
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}
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node, err := nodeSelector(service)
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node, err := r.opts.selector(service)
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if err != nil {
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if err != nil {
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return nil, err
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return nil, err
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}
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}
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84
examples/client/node_selector/node_selector.go
Normal file
84
examples/client/node_selector/node_selector.go
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@ -0,0 +1,84 @@
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package main
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import (
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"fmt"
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"math/rand"
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"time"
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"github.com/micro/go-micro/client"
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"github.com/micro/go-micro/cmd"
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c "github.com/micro/go-micro/context"
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"github.com/micro/go-micro/errors"
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example "github.com/micro/go-micro/examples/server/proto/example"
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"github.com/micro/go-micro/registry"
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"golang.org/x/net/context"
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)
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func init() {
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rand.Seed(time.Now().Unix())
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}
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// A random node selector
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func randomSelector(s []*registry.Service) (*registry.Node, error) {
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if len(s) == 0 {
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return nil, errors.NotFound("go.micro.client", "Service not found")
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}
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i := rand.Int()
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j := i % len(s)
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if len(s[j].Nodes) == 0 {
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return nil, errors.NotFound("go.micro.client", "Service not found")
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}
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n := i % len(s[j].Nodes)
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return s[j].Nodes[n], nil
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}
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// Wraps the node selector so that it will log what node was selected
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func wrapSelector(fn client.NodeSelector) client.NodeSelector {
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return func(s []*registry.Service) (*registry.Node, error) {
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n, err := fn(s)
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if err != nil {
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return nil, err
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}
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fmt.Printf("Selected node %v\n", n)
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return n, nil
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}
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}
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func call(i int) {
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// Create new request to service go.micro.srv.example, method Example.Call
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req := client.NewRequest("go.micro.srv.example", "Example.Call", &example.Request{
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Name: "John",
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})
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// create context with metadata
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ctx := c.WithMetadata(context.Background(), map[string]string{
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"X-User-Id": "john",
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"X-From-Id": "script",
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})
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rsp := &example.Response{}
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// Call service
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if err := client.Call(ctx, req, rsp); err != nil {
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fmt.Println("call err: ", err, rsp)
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return
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}
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fmt.Println("Call:", i, "rsp:", rsp.Msg)
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}
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func main() {
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cmd.Init()
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client.DefaultClient = client.NewClient(
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client.Selector(wrapSelector(randomSelector)),
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)
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fmt.Println("\n--- Call example ---\n")
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for i := 0; i < 10; i++ {
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call(i)
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}
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}
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