implement watcher

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

consul.go

@@ -3,10 +3,12 @@ package consul
 import (
 	"context"
 	"fmt"
+	"reflect"
 
 	"github.com/hashicorp/consul/api"
 	"github.com/imdario/mergo"
 	"github.com/unistack-org/micro/v3/config"
+	"github.com/unistack-org/micro/v3/util/jitter"
 	rutil "github.com/unistack-org/micro/v3/util/reflect"
 )
 
@@ -104,11 +106,16 @@ func (c *consulConfig) Load(ctx context.Context, opts ...config.LoadOption) erro
 			mopts = append(mopts, mergo.WithAppendSlice)
 		}
 
-		src, err := rutil.Zero(c.opts.Struct)
+		dst := c.opts.Struct
+		if options.Struct != nil {
+			dst = options.Struct
+		}
+
+		src, err := rutil.Zero(dst)
 		if err == nil {
 			err = c.opts.Codec.Unmarshal(pair.Value, src)
 			if err == nil {
-				err = mergo.Merge(c.opts.Struct, src, mopts...)
+				err = mergo.Merge(dst, src, mopts...)
 			}
 		}
 
@@ -160,6 +167,113 @@ func (c *consulConfig) Name() string {
 	return c.opts.Name
 }
 
+func (c *consulConfig) Watch(ctx context.Context, opts ...config.WatchOption) (config.Watcher, error) {
+	w := &consulWatcher{
+		cli:   c.cli,
+		path:  c.path,
+		opts:  c.opts,
+		wopts: config.NewWatchOptions(opts...),
+		done:  make(chan struct{}),
+		vchan: make(chan map[string]interface{}),
+		echan: make(chan error),
+	}
+
+	go w.run()
+
+	return w, nil
+}
+
+type consulWatcher struct {
+	cli   *api.Client
+	path  string
+	opts  config.Options
+	wopts config.WatchOptions
+	done  chan struct{}
+	vchan chan map[string]interface{}
+	echan chan error
+}
+
+func (w *consulWatcher) run() {
+	ticker := jitter.NewTicker(w.wopts.MinInterval, w.wopts.MaxInterval)
+	defer ticker.Stop()
+
+	src := w.opts.Struct
+	if w.wopts.Struct != nil {
+		src = w.wopts.Struct
+	}
+
+	for {
+		select {
+		case <-w.done:
+			return
+		case <-ticker.C:
+			dst, err := rutil.Zero(src)
+			if err != nil {
+				w.echan <- err
+				return
+			}
+
+			pair, _, err := w.cli.KV().Get(w.path, nil)
+			if err != nil {
+				w.echan <- err
+				return
+			}
+
+			if pair == nil {
+				w.echan <- fmt.Errorf("consul path %s not found", w.path)
+				return
+			}
+
+			err = w.opts.Codec.Unmarshal(pair.Value, dst)
+			if err != nil {
+				w.echan <- err
+				return
+			}
+
+			srcmp, err := rutil.StructFieldsMap(src)
+			if err != nil {
+				w.echan <- err
+				return
+			}
+
+			dstmp, err := rutil.StructFieldsMap(dst)
+			if err != nil {
+				w.echan <- err
+				return
+			}
+
+			for sk, sv := range srcmp {
+				if reflect.DeepEqual(dstmp[sk], sv) {
+					delete(dstmp, sk)
+				}
+			}
+
+			w.vchan <- dstmp
+			src = dst
+		}
+	}
+}
+
+func (w *consulWatcher) Next() (map[string]interface{}, error) {
+	select {
+	case <-w.done:
+		break
+	case err := <-w.echan:
+		return nil, err
+	case v, ok := <-w.vchan:
+		if !ok {
+			break
+		}
+		return v, nil
+	}
+	return nil, config.ErrWatcherStopped
+}
+
+func (w *consulWatcher) Stop() error {
+	close(w.done)
+	return nil
+}
+
 func NewConfig(opts ...config.Option) config.Config {
 	options := config.NewOptions(opts...)
 	if len(options.StructTag) == 0 {

go.mod

@@ -9,5 +9,5 @@ require (
 	github.com/hashicorp/golang-lru v0.5.3 // indirect
 	github.com/imdario/mergo v0.3.12
 	github.com/pkg/errors v0.9.1 // indirect
-	github.com/unistack-org/micro/v3 v3.4.0
+	github.com/unistack-org/micro/v3 v3.5.8
 )

go.sum

@@ -7,15 +7,15 @@ github.com/bgentry/speakeasy v0.1.0/go.mod h1:+zsyZBPWlz7T6j88CTgSN5bM796AkVf0kB
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/ef-ds/deque v1.0.4/go.mod h1:gXDnTC3yqvBcHbq2lcExjtAcVrOnJCbMcZXmuj8Z4tg=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
 github.com/fatih/color v1.9.0 h1:8xPHl4/q1VyqGIPif1F+1V3Y3lSmrq01EabUW3CoW5s=
 github.com/fatih/color v1.9.0/go.mod h1:eQcE1qtQxscV5RaZvpXrrb8Drkc3/DdQ+uUYCNjL+zU=
+github.com/golang-jwt/jwt v3.2.2+incompatible/go.mod h1:8pz2t5EyA70fFQQSrl6XZXzqecmYZeUEB8OUGHkxJ+I=
 github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
 github.com/google/btree v1.0.0 h1:0udJVsspx3VBr5FwtLhQQtuAsVc79tTq0ocGIPAU6qo=
 github.com/google/btree v1.0.0/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
-github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/consul/api v1.8.1 h1:BOEQaMWoGMhmQ29fC26bi0qb7/rId9JzZP2V0Xmx7m8=
 github.com/hashicorp/consul/api v1.8.1/go.mod h1:sDjTOq0yUyv5G4h+BqSea7Fn6BU+XbolEz1952UB+mk=
 github.com/hashicorp/consul/sdk v0.7.0 h1:H6R9d008jDcHPQPAqPNuydAshJ4v5/8URdFnUvK/+sc=
@@ -25,8 +25,6 @@ github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brv
 github.com/hashicorp/go-cleanhttp v0.5.1 h1:dH3aiDG9Jvb5r5+bYHsikaOUIpcM0xvgMXVoDkXMzJM=
 github.com/hashicorp/go-cleanhttp v0.5.1/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
 github.com/hashicorp/go-hclog v0.12.0/go.mod h1:whpDNt7SSdeAju8AWKIWsul05p54N/39EeqMAyrmvFQ=
-github.com/hashicorp/go-hclog v0.16.0 h1:uCeOEwSWGMwhJUdpUjk+1cVKIEfGu2/1nFXukimi2MU=
-github.com/hashicorp/go-hclog v0.16.0/go.mod h1:whpDNt7SSdeAju8AWKIWsul05p54N/39EeqMAyrmvFQ=
 github.com/hashicorp/go-hclog v0.16.1 h1:IVQwpTGNRRIHafnTs2dQLIk4ENtneRIEEJWOVDqz99o=
 github.com/hashicorp/go-hclog v0.16.1/go.mod h1:whpDNt7SSdeAju8AWKIWsul05p54N/39EeqMAyrmvFQ=
 github.com/hashicorp/go-immutable-radix v1.0.0 h1:AKDB1HM5PWEA7i4nhcpwOrO2byshxBjXVn/J/3+z5/0=
@@ -97,8 +95,8 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-github.com/unistack-org/micro/v3 v3.4.0 h1:z9F3lgAb2j4cZ1ib5qBj66JPYUAzR4sNIJqUDjVwyVQ=
+github.com/unistack-org/micro/v3 v3.5.8 h1:7kuNW7Pih3LYUA0DuVt9l87LjtT4rsqDFyTYLrLtNNI=
-github.com/unistack-org/micro/v3 v3.4.0/go.mod h1:LXmPfbJnJNvL0kQs8HfnkV3Wya2Wb+C7keVq++RCZnk=
+github.com/unistack-org/micro/v3 v3.5.8/go.mod h1:zQnZPEy842kQNcyjmVys6tdMjty4PHdyUUKYm1wrg1s=
 golang.org/x/crypto v0.0.0-20181029021203-45a5f77698d3/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190923035154-9ee001bba392 h1:ACG4HJsFiNMf47Y4PeRoebLNy/2lXT9EtprMuTFWt1M=