add copy metadata from grpc-go (#386)

Co-authored-by: Василий Толстов <v.tolstov@unistack.org>
Co-authored-by: Vasiliy Tolstov <v.tolstov@unistack.org>
Co-authored-by: vtolstov <vtolstov@users.noreply.github.com>
Reviewed-on: #386
Co-authored-by: Evstigneev Denis <danteevstigneev@yandex.ru>
Co-committed-by: Evstigneev Denis <danteevstigneev@yandex.ru>

.gitea/workflows/job_coverage.yml

@@ -26,24 +26,24 @@ jobs:
 
     - name: test coverage
       run: |
-        go test -v -cover ./... -coverprofile coverage.out -coverpkg ./...
+        go test -v -cover ./... -covermode=count -coverprofile coverage.out -coverpkg ./...
         go tool cover -func coverage.out -o coverage.out
 
     - name: coverage badge
-      uses: tj-actions/coverage-badge-go@v1
+      uses: tj-actions/coverage-badge-go@v2
       with:
         green: 80
         filename: coverage.out
 
     - uses: stefanzweifel/git-auto-commit-action@v4
-      id: auto-commit-action
+      name: autocommit
       with:
         commit_message: Apply Code Coverage Badge
         skip_fetch: true
         skip_checkout: true
         file_pattern: ./README.md
 
-    - name: Push Changes
+    - name: push
       if: steps.auto-commit-action.outputs.changes_detected == 'true'
       uses: ad-m/github-push-action@master
       with:

README.md

@@ -1,5 +1,9 @@
-# Micro 
+# Micro
-![Coverage](https://img.shields.io/badge/Coverage-45.1%25-yellow)
+![Coverage](https://img.shields.io/badge/Coverage-44.6%25-yellow)
+[![License](https://img.shields.io/:license-apache-blue.svg)](https://opensource.org/licenses/Apache-2.0)
+[![Doc](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white&style=flat-square)](https://pkg.go.dev/go.unistack.org/micro/v3?tab=overview)
+[![Status](https://git.unistack.org/unistack-org/micro/actions/workflows/job_tests.yml/badge.svg?branch=v3)](https://git.unistack.org/unistack-org/micro/actions?query=workflow%3Abuild+branch%3Av3+event%3Apush)
+[![Lint](https://goreportcard.com/badge/go.unistack.org/micro/v3)](https://goreportcard.com/report/go.unistack.org/micro/v3)
 
 Micro is a standard library for microservices.
 
@@ -11,30 +15,20 @@ Micro provides the core requirements for distributed systems development includi
 
 Micro abstracts away the details of distributed systems. Here are the main features.
 
-- **Authentication** - Auth is built in as a first class citizen. Authentication and authorization enable secure 
-zero trust networking by providing every service an identity and certificates. This additionally includes rule 
-based access control.
-
 - **Dynamic Config** - Load and hot reload dynamic config from anywhere. The config interface provides a way to load application 
-level config from any source such as env vars, file, etcd. You can merge the sources and even define fallbacks.
+level config from any source such as env vars, cmdline, file, consul, vault... You can merge the sources and even define fallbacks.
 
 - **Data Storage** - A simple data store interface to read, write and delete records. It includes support for memory, file and 
-CockroachDB by default. State and persistence becomes a core requirement beyond prototyping and Micro looks to build that into the framework.
+s3. State and persistence becomes a core requirement beyond prototyping and Micro looks to build that into the framework.
 
 - **Service Discovery** - Automatic service registration and name resolution. Service discovery is at the core of micro service 
 development. When service A needs to speak to service B it needs the location of that service.
 
-- **Load Balancing** - Client side load balancing built on service discovery. Once we have the addresses of any number of instances 
-of a service we now need a way to decide which node to route to. We use random hashed load balancing to provide even distribution 
-across the services and retry a different node if there's a problem. 
-
 - **Message Encoding** - Dynamic message encoding based on content-type. The client and server will use codecs along with content-type 
 to seamlessly encode and decode Go types for you. Any variety of messages could be encoded and sent from different clients. The client 
 and server handle this by default.
 
-- **Transport** - gRPC or http based request/response with support for bidirectional streaming. We provide an abstraction for synchronous communication. A request made to a service will be automatically resolved, load balanced, dialled and streamed.
+- **Async Messaging** - Pub/Sub is built in as a first class citizen for asynchronous communication and event driven architectures.
-
-- **Async Messaging** - PubSub is built in as a first class citizen for asynchronous communication and event driven architectures.
 Event notifications are a core pattern in micro service development.
 
 - **Synchronization** - Distributed systems are often built in an eventually consistent manner. Support for distributed locking and 
@@ -43,10 +37,6 @@ leadership are built in as a Sync interface. When using an eventually consistent
 - **Pluggable Interfaces** - Micro makes use of Go interfaces for each system abstraction. Because of this these interfaces 
 are pluggable and allows Micro to be runtime agnostic.
 
-## Getting Started
-
-To be created.
-
 ## License
 
 Micro is Apache 2.0 licensed.

broker/broker.go

@@ -6,8 +6,8 @@ import (
 	"errors"
 	"time"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 // DefaultBroker default memory broker

broker/memory/memory.go

@@ -4,14 +4,14 @@ import (
 	"context"
 	"sync"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	maddr "go.unistack.org/micro/v3/util/addr"
+	maddr "go.unistack.org/micro/v4/util/addr"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
-	mnet "go.unistack.org/micro/v3/util/net"
+	mnet "go.unistack.org/micro/v4/util/net"
-	"go.unistack.org/micro/v3/util/rand"
+	"go.unistack.org/micro/v4/util/rand"
 )
 
 type memoryBroker struct {

broker/memory/memory_test.go

@@ -5,8 +5,8 @@ import (
 	"fmt"
 	"testing"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 func TestMemoryBatchBroker(t *testing.T) {

broker/noop.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"strings"
 
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
 )
 
 type NoopBroker struct {

broker/options.go

@@ -5,13 +5,13 @@ import (
 	"crypto/tls"
 	"time"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/sync"
+	"go.unistack.org/micro/v4/sync"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options struct

client/backoff.go

@@ -5,7 +5,7 @@ import (
 	"math"
 	"time"
 
-	"go.unistack.org/micro/v3/util/backoff"
+	"go.unistack.org/micro/v4/util/backoff"
 )
 
 // BackoffFunc is the backoff call func

client/client.go

@@ -5,8 +5,8 @@ import (
 	"context"
 	"time"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 var (

client/lookup.go

@@ -4,8 +4,8 @@ import (
 	"context"
 	"sort"
 
-	"go.unistack.org/micro/v3/errors"
+	"go.unistack.org/micro/v4/errors"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
 )
 
 // LookupFunc is used to lookup routes for a service

client/noop.go

@@ -7,14 +7,14 @@ import (
 	"strconv"
 	"time"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/errors"
+	"go.unistack.org/micro/v4/errors"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/selector"
+	"go.unistack.org/micro/v4/selector"
-	"go.unistack.org/micro/v3/semconv"
+	"go.unistack.org/micro/v4/semconv"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // DefaultCodecs will be used to encode/decode data
@@ -588,7 +588,6 @@ func (n *noopClient) publish(ctx context.Context, ps []Message, opts ...PublishO
 
 	for _, p := range ps {
 		md := metadata.Copy(omd)
-		md[metadata.HeaderContentType] = p.ContentType()
 		topic := p.Topic()
 		if len(exchange) > 0 {
 			topic = exchange
@@ -600,6 +599,8 @@ func (n *noopClient) publish(ctx context.Context, ps []Message, opts ...PublishO
 			md.Set(k, v)
 		}
 
+		md[metadata.HeaderContentType] = p.ContentType()
+
 		var body []byte
 
 		// passed in raw data

client/options.go

@@ -6,17 +6,17 @@ import (
 	"net"
 	"time"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	"go.unistack.org/micro/v3/selector"
+	"go.unistack.org/micro/v4/selector"
-	"go.unistack.org/micro/v3/selector/random"
+	"go.unistack.org/micro/v4/selector/random"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options holds client options

client/retry.go

@@ -3,7 +3,7 @@ package client
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/errors"
+	"go.unistack.org/micro/v4/errors"
 )
 
 // RetryFunc that returning either false or a non-nil error will result in the call not being retried

client/retry_test.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"testing"
 
-	"go.unistack.org/micro/v3/errors"
+	"go.unistack.org/micro/v4/errors"
 )
 
 func TestRetryAlways(t *testing.T) {

client/test_request.go

@@ -1,7 +1,7 @@
 package client
 
 import (
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
 )
 
 type testRequest struct {

cluster/cluster.go

@@ -3,7 +3,7 @@ package cluster
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 // Message sent to member in cluster

codec/options.go

@@ -3,9 +3,9 @@ package codec
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Option func

config/default.go

@@ -9,10 +9,10 @@ import (
 
 	"dario.cat/mergo"
 	"github.com/google/uuid"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	mid "go.unistack.org/micro/v3/util/id"
+	mid "go.unistack.org/micro/v4/util/id"
-	rutil "go.unistack.org/micro/v3/util/reflect"
+	rutil "go.unistack.org/micro/v4/util/reflect"
-	mtime "go.unistack.org/micro/v3/util/time"
+	mtime "go.unistack.org/micro/v4/util/time"
 )
 
 type defaultConfig struct {
@@ -210,7 +210,7 @@ func fillValue(value reflect.Value, val string) error {
 				return err
 			}
 			value.Set(reflect.ValueOf(v))
-		case value.Type().String() == "time.Duration" && value.Type().PkgPath() == "go.unistack.org/micro/v3/util/time":
+		case value.Type().String() == "time.Duration" && value.Type().PkgPath() == "go.unistack.org/micro/v4/util/time":
 			v, err := mtime.ParseDuration(val)
 			if err != nil {
 				return err

config/default_test.go

@@ -7,8 +7,8 @@ import (
 	"testing"
 	"time"
 
-	"go.unistack.org/micro/v3/config"
+	"go.unistack.org/micro/v4/config"
-	mtime "go.unistack.org/micro/v3/util/time"
+	mtime "go.unistack.org/micro/v4/util/time"
 )
 
 type cfg struct {

config/options.go

@@ -4,11 +4,11 @@ import (
 	"context"
 	"time"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options hold the config options

event.go

@@ -3,7 +3,7 @@ package micro
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
 )
 
 // Event is used to publish messages to a topic

flow/default.go

@@ -6,12 +6,12 @@ import (
 	"sync"
 
 	"github.com/silas/dag"
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/store"
+	"go.unistack.org/micro/v4/store"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 type microFlow struct {

flow/flow.go

@@ -7,7 +7,7 @@ import (
 	"sync"
 	"sync/atomic"
 
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 var (

flow/options.go

@@ -4,11 +4,11 @@ import (
 	"context"
 	"time"
 
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/store"
+	"go.unistack.org/micro/v4/store"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Option func

fsm/fsm_test.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"testing"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
 )
 
 func TestFSMStart(t *testing.T) {

go.mod

@@ -1,11 +1,11 @@
-module go.unistack.org/micro/v3
+module go.unistack.org/micro/v4
 
 go 1.22.0
 
 require (
 	dario.cat/mergo v1.0.1
 	github.com/DATA-DOG/go-sqlmock v1.5.2
-	github.com/KimMachineGun/automemlimit v0.6.1
+	github.com/KimMachineGun/automemlimit v0.7.0
 	github.com/ash3in/uuidv8 v1.2.0
 	github.com/google/uuid v1.6.0
 	github.com/matoous/go-nanoid v1.5.1
@@ -14,8 +14,8 @@ require (
 	go.uber.org/automaxprocs v1.6.0
 	go.unistack.org/micro-proto/v3 v3.4.1
 	golang.org/x/sync v0.10.0
-	google.golang.org/grpc v1.69.2
+	google.golang.org/grpc v1.69.4
-	google.golang.org/protobuf v1.36.1
+	google.golang.org/protobuf v1.36.3
 	gopkg.in/yaml.v3 v3.0.1
 )
 
@@ -36,8 +36,8 @@ require (
 	github.com/stretchr/testify v1.10.0 // indirect
 	go.uber.org/goleak v1.3.0 // indirect
 	golang.org/x/exp v0.0.0-20241210194714-1829a127f884 // indirect
-	golang.org/x/net v0.33.0 // indirect
+	golang.org/x/net v0.34.0 // indirect
-	golang.org/x/sys v0.28.0 // indirect
+	golang.org/x/sys v0.29.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20241216192217-9240e9c98484 // indirect
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
 )

logger/options.go

@@ -8,7 +8,7 @@ import (
 	"slices"
 	"time"
 
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
 )
 
 // Option func signature

logger/slog/slog.go

@@ -13,9 +13,9 @@ import (
 	"sync/atomic"
 	"time"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/semconv"
+	"go.unistack.org/micro/v4/semconv"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 const (

logger/slog/slog_test.go

@@ -12,8 +12,9 @@ import (
 	"time"
 
 	"github.com/google/uuid"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
+	"go.unistack.org/micro/v4/util/buffer"
 )
 
 // always first to have proper check
@@ -30,11 +31,30 @@ func TestStacktrace(t *testing.T) {
 
 	l.Error(ctx, "msg1", errors.New("err"))
 
-	if !bytes.Contains(buf.Bytes(), []byte(`slog_test.go:31`)) {
+	if !bytes.Contains(buf.Bytes(), []byte(`slog_test.go:32`)) {
 		t.Fatalf("logger error not works, buf contains: %s", buf.Bytes())
 	}
 }
 
+func TestDelayedBuffer(t *testing.T) {
+	ctx := context.TODO()
+	buf := bytes.NewBuffer(nil)
+	dbuf := buffer.NewDelayedBuffer(100, 100*time.Millisecond, buf)
+	l := NewLogger(logger.WithLevel(logger.ErrorLevel), logger.WithOutput(dbuf),
+		WithHandlerFunc(slog.NewTextHandler),
+		logger.WithAddStacktrace(true),
+	)
+	if err := l.Init(logger.WithFields("key1", "val1")); err != nil {
+		t.Fatal(err)
+	}
+
+	l.Error(ctx, "msg1", errors.New("err"))
+	time.Sleep(120 * time.Millisecond)
+	if !bytes.Contains(buf.Bytes(), []byte(`key1=val1`)) {
+		t.Fatalf("logger delayed buffer not works, buf contains: %s", buf.Bytes())
+	}
+}
+
 func TestTime(t *testing.T) {
 	ctx := context.TODO()
 	buf := bytes.NewBuffer(nil)

logger/unwrap/unwrap.go

@@ -8,7 +8,7 @@ import (
 	"strconv"
 	"strings"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
 )
 
 const sf = "0-+# "

logger/unwrap/unwrap_test.go

@@ -5,7 +5,7 @@ import (
 	"strings"
 	"testing"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
 )
 
 func TestUnwrap(t *testing.T) {

metadata/context.go

@@ -1,3 +1,5 @@
+//go:build !exclude
+
 // Package metadata is a way of defining message headers
 package metadata
 

metadata/metadata.go

@@ -1,3 +1,5 @@
+//go:build !exclude
+
 // Package metadata is a way of defining message headers
 package metadata
 

metadata/metadata_grpc.go

@@ -0,0 +1,282 @@
+//go:build exclude
+
+// Package metadata TODO need compare with micro metadata
+package metadata // import "google.golang.org/grpc/metadata"
+
+import (
+	"context"
+	"fmt"
+	"strings"
+)
+
+// MD is a mapping from metadata keys to values. Users should use the following
+// two convenience functions New and Pairs to generate MD.
+type MD map[string][]string
+
+type Metadata map[string]string
+
+// New creates an MD from a given key-value map.
+//
+// Only the following ASCII characters are allowed in keys:
+//   - digits: 0-9
+//   - uppercase letters: A-Z (normalized to lower)
+//   - lowercase letters: a-z
+//   - special characters: -_.
+//
+// Uppercase letters are automatically converted to lowercase.
+//
+// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
+// result in errors if set in metadata.
+func New(m map[string]string) MD {
+	md := make(MD, len(m))
+	for k, val := range m {
+		key := strings.ToLower(k)
+		md[key] = append(md[key], val)
+	}
+	return md
+}
+
+// Pairs returns an MD formed by the mapping of key, value ...
+// Pairs panics if len(kv) is odd.
+//
+// Only the following ASCII characters are allowed in keys:
+//   - digits: 0-9
+//   - uppercase letters: A-Z (normalized to lower)
+//   - lowercase letters: a-z
+//   - special characters: -_.
+//
+// Uppercase letters are automatically converted to lowercase.
+//
+// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
+// result in errors if set in metadata.
+func Pairs(kv ...string) MD {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: Pairs got the odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md := make(MD, len(kv)/2)
+	for i := 0; i < len(kv); i += 2 {
+		key := strings.ToLower(kv[i])
+		md[key] = append(md[key], kv[i+1])
+	}
+	return md
+}
+
+// Len returns the number of items in md.
+func (md MD) Len() int {
+	return len(md)
+}
+
+// Copy returns a copy of md.
+func (md MD) Copy() MD {
+	out := make(MD, len(md))
+	for k, v := range md {
+		out[k] = copyOf(v)
+	}
+	return out
+}
+
+// Get obtains the values for a given key.
+//
+// k is converted to lowercase before searching in md.
+func (md MD) Get(k string) []string {
+	k = strings.ToLower(k)
+	return md[k]
+}
+
+// Set sets the value of a given key with a slice of values.
+//
+// k is converted to lowercase before storing in md.
+func (md MD) Set(k string, vals ...string) {
+	if len(vals) == 0 {
+		return
+	}
+	k = strings.ToLower(k)
+	md[k] = vals
+}
+
+// Append adds the values to key k, not overwriting what was already stored at
+// that key.
+//
+// k is converted to lowercase before storing in md.
+func (md MD) Append(k string, vals ...string) {
+	if len(vals) == 0 {
+		return
+	}
+	k = strings.ToLower(k)
+	md[k] = append(md[k], vals...)
+}
+
+// Delete removes the values for a given key k which is converted to lowercase
+// before removing it from md.
+func (md MD) Delete(k string) {
+	k = strings.ToLower(k)
+	delete(md, k)
+}
+
+// Join joins any number of mds into a single MD.
+//
+// The order of values for each key is determined by the order in which the mds
+// containing those values are presented to Join.
+func Join(mds ...MD) MD {
+	out := MD{}
+	for _, md := range mds {
+		for k, v := range md {
+			out[k] = append(out[k], v...)
+		}
+	}
+	return out
+}
+
+type mdIncomingKey struct{}
+type mdOutgoingKey struct{}
+
+// NewIncomingContext creates a new context with incoming md attached. md must
+// not be modified after calling this function.
+func NewIncomingContext(ctx context.Context, md Metadata) context.Context {
+	in := make(MD, len(md))
+	for k, v := range md {
+		in[k] = []string{v}
+	}
+
+	return context.WithValue(ctx, mdIncomingKey{}, in)
+}
+
+// NewOutgoingContext creates a new context with outgoing md attached. If used
+// in conjunction with AppendToOutgoingContext, NewOutgoingContext will
+// overwrite any previously-appended metadata. md must not be modified after
+// calling this function.
+func NewOutgoingContext(ctx context.Context, md Metadata) context.Context {
+	out := make(MD, len(md))
+	for k, v := range md {
+		out[k] = []string{v}
+	}
+
+	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: out})
+}
+
+// AppendToOutgoingContext returns a new context with the provided kv merged
+// with any existing metadata in the context. Please refer to the documentation
+// of Pairs for a description of kv.
+func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: AppendToOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md, _ := ctx.Value(mdOutgoingKey{}).(rawMD)
+	added := make([][]string, len(md.added)+1)
+	copy(added, md.added)
+	kvCopy := make([]string, 0, len(kv))
+	for i := 0; i < len(kv); i += 2 {
+		kvCopy = append(kvCopy, strings.ToLower(kv[i]), kv[i+1])
+	}
+	added[len(added)-1] = kvCopy
+	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md.md, added: added})
+}
+
+// FromIncomingContext returns the incoming metadata in ctx if it exists.
+//
+// All keys in the returned MD are lowercase.
+func FromIncomingContext(ctx context.Context) (Metadata, bool) {
+	md, ok := ctx.Value(mdIncomingKey{}).(MD)
+	if !ok {
+		return nil, false
+	}
+	out := make(Metadata, len(md))
+	for k, v := range md {
+		// We need to manually convert all keys to lower case, because MD is a
+		// map, and there's no guarantee that the MD attached to the context is
+		// created using our helper functions.
+
+		if len(v) > 0 {
+			key := strings.ToLower(k)
+			out[key] = v[0]
+		}
+
+	}
+	return out, true
+}
+
+// ValueFromIncomingContext returns the metadata value corresponding to the metadata
+// key from the incoming metadata if it exists. Keys are matched in a case insensitive
+// manner.
+func ValueFromIncomingContext(ctx context.Context, key string) []string {
+	md, ok := ctx.Value(mdIncomingKey{}).(MD)
+	if !ok {
+		return nil
+	}
+
+	if v, ok := md[key]; ok {
+		return copyOf(v)
+	}
+	for k, v := range md {
+		// Case insensitive comparison: MD is a map, and there's no guarantee
+		// that the MD attached to the context is created using our helper
+		// functions.
+		if strings.EqualFold(k, key) {
+			return copyOf(v)
+		}
+	}
+	return nil
+}
+
+func copyOf(v []string) []string {
+	vals := make([]string, len(v))
+	copy(vals, v)
+	return vals
+}
+
+// fromOutgoingContextRaw returns the un-merged, intermediary contents of rawMD.
+//
+// Remember to perform strings.ToLower on the keys, for both the returned MD (MD
+// is a map, there's no guarantee it's created using our helper functions) and
+// the extra kv pairs (AppendToOutgoingContext doesn't turn them into
+// lowercase).
+func fromOutgoingContextRaw(ctx context.Context) (MD, [][]string, bool) {
+	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
+	if !ok {
+		return nil, nil, false
+	}
+
+	return raw.md, raw.added, true
+}
+
+// FromOutgoingContext returns the outgoing metadata in ctx if it exists.
+//
+// All keys in the returned MD are lowercase.
+func FromOutgoingContext(ctx context.Context) (Metadata, bool) {
+	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
+	if !ok {
+		return nil, false
+	}
+
+	mdSize := len(raw.md)
+	for i := range raw.added {
+		mdSize += len(raw.added[i]) / 2
+	}
+
+	out := make(Metadata, mdSize)
+	for k, v := range raw.md {
+		// We need to manually convert all keys to lower case, because MD is a
+		// map, and there's no guarantee that the MD attached to the context is
+		// created using our helper functions.
+		if len(v) > 0 {
+			key := strings.ToLower(k)
+			out[key] = v[0]
+		}
+	}
+	for _, added := range raw.added {
+		if len(added)%2 == 1 {
+			panic(fmt.Sprintf("metadata: FromOutgoingContext got an odd number of input pairs for metadata: %d", len(added)))
+		}
+
+		for i := 0; i < len(added); i += 2 {
+			key := strings.ToLower(added[i])
+			out[key] = added[i+1]
+		}
+	}
+	return out, ok
+}
+
+type rawMD struct {
+	md    MD
+	added [][]string
+}

micro.go

@@ -3,21 +3,21 @@ package micro
 import (
 	"reflect"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/flow"
+	"go.unistack.org/micro/v4/flow"
-	"go.unistack.org/micro/v3/fsm"
+	"go.unistack.org/micro/v4/fsm"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/resolver"
+	"go.unistack.org/micro/v4/resolver"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	"go.unistack.org/micro/v3/selector"
+	"go.unistack.org/micro/v4/selector"
-	"go.unistack.org/micro/v3/server"
+	"go.unistack.org/micro/v4/server"
-	"go.unistack.org/micro/v3/store"
+	"go.unistack.org/micro/v4/store"
-	"go.unistack.org/micro/v3/sync"
+	"go.unistack.org/micro/v4/sync"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 func As(b any, target any) bool {

micro_test.go

@@ -6,8 +6,8 @@ import (
 	"reflect"
 	"testing"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/fsm"
+	"go.unistack.org/micro/v4/fsm"
 )
 
 func TestAs(t *testing.T) {

network/network.go

@@ -2,8 +2,8 @@
 package network
 
 import (
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/server"
+	"go.unistack.org/micro/v4/server"
 )
 
 // Error is network node errors

network/options.go

@@ -1,13 +1,13 @@
 package network
 
 import (
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/network/tunnel"
+	"go.unistack.org/micro/v4/network/tunnel"
-	"go.unistack.org/micro/v3/proxy"
+	"go.unistack.org/micro/v4/proxy"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 // Option func

network/transport/memory.go

@@ -8,9 +8,9 @@ import (
 	"sync"
 	"time"
 
-	maddr "go.unistack.org/micro/v3/util/addr"
+	maddr "go.unistack.org/micro/v4/util/addr"
-	mnet "go.unistack.org/micro/v3/util/net"
+	mnet "go.unistack.org/micro/v4/util/net"
-	"go.unistack.org/micro/v3/util/rand"
+	"go.unistack.org/micro/v4/util/rand"
 )
 
 type memorySocket struct {

network/transport/options.go

@@ -5,10 +5,10 @@ import (
 	"crypto/tls"
 	"time"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options struct holds the transport options

network/transport/transport.go

@@ -5,7 +5,7 @@ import (
 	"context"
 	"time"
 
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 var (

network/tunnel/broker/broker.go

@@ -5,11 +5,11 @@ import (
 	"context"
 	"fmt"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/network/transport"
+	"go.unistack.org/micro/v4/network/transport"
-	"go.unistack.org/micro/v3/network/tunnel"
+	"go.unistack.org/micro/v4/network/tunnel"
 )
 
 type tunBroker struct {

network/tunnel/options.go

@@ -3,11 +3,11 @@ package tunnel
 import (
 	"time"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/network/transport"
+	"go.unistack.org/micro/v4/network/transport"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 var (

network/tunnel/transport/listener.go

@@ -1,8 +1,8 @@
 package transport
 
 import (
-	"go.unistack.org/micro/v3/network/transport"
+	"go.unistack.org/micro/v4/network/transport"
-	"go.unistack.org/micro/v3/network/tunnel"
+	"go.unistack.org/micro/v4/network/tunnel"
 )
 
 type tunListener struct {

network/tunnel/transport/transport.go

@@ -5,8 +5,8 @@ import (
 	"context"
 	"fmt"
 
-	"go.unistack.org/micro/v3/network/transport"
+	"go.unistack.org/micro/v4/network/transport"
-	"go.unistack.org/micro/v3/network/tunnel"
+	"go.unistack.org/micro/v4/network/tunnel"
 )
 
 type tunTransport struct {

network/tunnel/tunnel.go

@@ -6,7 +6,7 @@ import (
 	"errors"
 	"time"
 
-	"go.unistack.org/micro/v3/network/transport"
+	"go.unistack.org/micro/v4/network/transport"
 )
 
 // DefaultTunnel contains default tunnel implementation

options.go

@@ -5,17 +5,17 @@ import (
 	"fmt"
 	"time"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/config"
+	"go.unistack.org/micro/v4/config"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	"go.unistack.org/micro/v3/server"
+	"go.unistack.org/micro/v4/server"
-	"go.unistack.org/micro/v3/store"
+	"go.unistack.org/micro/v4/store"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options for micro service

profiler/http/http.go

@@ -7,7 +7,7 @@ import (
 	"net/http/pprof"
 	"sync"
 
-	profile "go.unistack.org/micro/v3/profiler"
+	profile "go.unistack.org/micro/v4/profiler"
 )
 
 type httpProfile struct {

profiler/pprof/pprof.go

@@ -9,7 +9,7 @@ import (
 	"sync"
 	"time"
 
-	profile "go.unistack.org/micro/v3/profiler"
+	profile "go.unistack.org/micro/v4/profiler"
 )
 
 type profiler struct {

proxy/options.go

@@ -2,11 +2,11 @@
 package proxy
 
 import (
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options for proxy

proxy/proxy.go

@@ -4,7 +4,7 @@ package proxy
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/server"
+	"go.unistack.org/micro/v4/server"
 )
 
 // DefaultEndpoint holds default proxy address

register/memory/memory.go

@@ -6,9 +6,9 @@ import (
 	"sync"
 	"time"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 var (
@@ -149,7 +149,7 @@ func (m *memory) Register(_ context.Context, s *register.Service, opts ...regist
 			m.opts.Logger.Debug(m.opts.Context, fmt.Sprintf("Register added new service: %s, version: %s", s.Name, s.Version))
 		}
 		m.records[options.Namespace] = srvs
-		go m.sendEvent(&register.Result{Action: "create", Service: s})
+		go m.sendEvent(&register.Result{Action: register.EventCreate, Service: s})
 	}
 
 	var addedNodes bool
@@ -185,7 +185,7 @@ func (m *memory) Register(_ context.Context, s *register.Service, opts ...regist
 		if m.opts.Logger.V(logger.DebugLevel) {
 			m.opts.Logger.Debug(m.opts.Context, fmt.Sprintf("Register added new node to service: %s, version: %s", s.Name, s.Version))
 		}
-		go m.sendEvent(&register.Result{Action: "update", Service: s})
+		go m.sendEvent(&register.Result{Action: register.EventUpdate, Service: s})
 	} else {
 		// refresh TTL and timestamp
 		for _, n := range s.Nodes {
@@ -238,7 +238,7 @@ func (m *memory) Deregister(ctx context.Context, s *register.Service, opts ...re
 	// is cleanup
 	if len(version.Nodes) > 0 {
 		m.records[options.Namespace][s.Name][s.Version] = version
-		go m.sendEvent(&register.Result{Action: "update", Service: s})
+		go m.sendEvent(&register.Result{Action: register.EventUpdate, Service: s})
 		return nil
 	}
 
@@ -246,7 +246,7 @@ func (m *memory) Deregister(ctx context.Context, s *register.Service, opts ...re
 	// register and exit
 	if len(versions) == 1 {
 		delete(m.records[options.Namespace], s.Name)
-		go m.sendEvent(&register.Result{Action: "delete", Service: s})
+		go m.sendEvent(&register.Result{Action: register.EventDelete, Service: s})
 
 		if m.opts.Logger.V(logger.DebugLevel) {
 			m.opts.Logger.Debug(m.opts.Context, fmt.Sprintf("Register removed service: %s", s.Name))
@@ -256,7 +256,7 @@ func (m *memory) Deregister(ctx context.Context, s *register.Service, opts ...re
 
 	// there are other versions of the service running, so only remove this version of it
 	delete(m.records[options.Namespace][s.Name], s.Version)
-	go m.sendEvent(&register.Result{Action: "delete", Service: s})
+	go m.sendEvent(&register.Result{Action: register.EventDelete, Service: s})
 	if m.opts.Logger.V(logger.DebugLevel) {
 		m.opts.Logger.Debug(m.opts.Context, fmt.Sprintf("Register removed service: %s, version: %s", s.Name, s.Version))
 	}

register/memory/memory_test.go

@@ -7,7 +7,7 @@ import (
 	"testing"
 	"time"
 
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
 )
 
 var testData = map[string][]*register.Service{

register/options.go

@@ -5,9 +5,10 @@ import (
 	"crypto/tls"
 	"time"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/meter"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options holds options for register
@@ -26,6 +27,8 @@ type Options struct {
 	Name string
 	// Addrs specifies register addrs
 	Addrs []string
+	// Codec used to marshal/unmarshal data in register
+	Codec codec.Codec
 	// Timeout specifies timeout
 	Timeout time.Duration
 }
@@ -37,6 +40,7 @@ func NewOptions(opts ...Option) Options {
 		Meter:   meter.DefaultMeter,
 		Tracer:  tracer.DefaultTracer,
 		Context: context.Background(),
+		Codec:   codec.NewCodec(),
 	}
 	for _, o := range opts {
 		o(&options)
@@ -130,6 +134,7 @@ func NewLookupOptions(opts ...LookupOption) LookupOptions {
 
 // ListOptions holds the list options for list method
 type ListOptions struct {
+	// Context used to store additional options
 	Context context.Context
 	// Namespace to scope the request to
 	Namespace string
@@ -300,3 +305,9 @@ func Name(n string) Option {
 		o.Name = n
 	}
 }
+
+func Codec(c codec.Codec) Option {
+	return func(o *Options) {
+		o.Codec = c
+	}
+}

register/register.go

@@ -5,7 +5,7 @@ import (
 	"context"
 	"errors"
 
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 const (

register/watcher.go

@@ -15,31 +15,31 @@ type Watcher interface {
 // the watcher. Actions can be create, update, delete
 type Result struct {
 	// Service holds register service
-	Service *Service
+	Service *Service `json:"service,omitempty"`
 	// Action holds the action
-	Action string
+	Action EventType `json:"action,omitempty"`
 }
 
 // EventType defines register event type
 type EventType int
 
 const (
-	// Create is emitted when a new service is registered
+	// EventCreate is emitted when a new service is registered
-	Create EventType = iota
+	EventCreate EventType = iota
-	// Delete is emitted when an existing service is deregistered
+	// EventDelete is emitted when an existing service is deregistered
-	Delete
+	EventDelete
-	// Update is emitted when an existing service is updated
+	// EventUpdate is emitted when an existing service is updated
-	Update
+	EventUpdate
 )
 
 // String returns human readable event type
 func (t EventType) String() string {
 	switch t {
-	case Create:
+	case EventCreate:
 		return "create"
-	case Delete:
+	case EventDelete:
 		return "delete"
-	case Update:
+	case EventUpdate:
 		return "update"
 	default:
 		return "unknown"
@@ -49,11 +49,11 @@ func (t EventType) String() string {
 // Event is register event
 type Event struct {
 	// Timestamp is event timestamp
-	Timestamp time.Time
+	Timestamp time.Time `json:"timestamp,omitempty"`
 	// Service is register service
-	Service *Service
+	Service *Service `json:"service,omitempty"`
 	// ID is register id
-	ID string
+	ID string `json:"id,omitempty"`
 	// Type defines type of event
-	Type EventType
+	Type EventType `json:"type,omitempty"`
 }

resolver/dns/dns.go

@@ -7,7 +7,7 @@ import (
 	"sync"
 	"time"
 
-	"go.unistack.org/micro/v3/resolver"
+	"go.unistack.org/micro/v4/resolver"
 )
 
 // Resolver is a DNS network resolve

resolver/dnssrv/dnssrv.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"net"
 
-	"go.unistack.org/micro/v3/resolver"
+	"go.unistack.org/micro/v4/resolver"
 )
 
 // Resolver is a DNS network resolve

resolver/http/http.go

@@ -8,7 +8,7 @@ import (
 	"net/http"
 	"net/url"
 
-	"go.unistack.org/micro/v3/resolver"
+	"go.unistack.org/micro/v4/resolver"
 )
 
 // nolint: golint,revive

resolver/noop/noop.go

@@ -2,7 +2,7 @@
 package noop
 
 import (
-	"go.unistack.org/micro/v3/resolver"
+	"go.unistack.org/micro/v4/resolver"
 )
 
 // Resolver contains noop resolver

resolver/registry/registry.go

@@ -4,8 +4,8 @@ package register
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/resolver"
+	"go.unistack.org/micro/v4/resolver"
 )
 
 // Resolver is a register network resolver

resolver/static/static.go

@@ -2,7 +2,7 @@
 package static
 
 import (
-	"go.unistack.org/micro/v3/resolver"
+	"go.unistack.org/micro/v4/resolver"
 )
 
 // Resolver returns a static list of nodes. In the event the node list

router/options.go

@@ -3,9 +3,9 @@ package router
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 // Options are router options

router/route.go

@@ -3,7 +3,7 @@ package router
 import (
 	"hash/fnv"
 
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 var (

selector/random/random.go

@@ -1,8 +1,8 @@
 package random
 
 import (
-	"go.unistack.org/micro/v3/selector"
+	"go.unistack.org/micro/v4/selector"
-	"go.unistack.org/micro/v3/util/rand"
+	"go.unistack.org/micro/v4/util/rand"
 )
 
 type random struct{}

selector/random/random_test.go

@@ -3,7 +3,7 @@ package random
 import (
 	"testing"
 
-	"go.unistack.org/micro/v3/selector"
+	"go.unistack.org/micro/v4/selector"
 )
 
 func TestRandom(t *testing.T) {

selector/roundrobin/roundrobin.go

@@ -1,8 +1,8 @@
 package roundrobin
 
 import (
-	"go.unistack.org/micro/v3/selector"
+	"go.unistack.org/micro/v4/selector"
-	"go.unistack.org/micro/v3/util/rand"
+	"go.unistack.org/micro/v4/util/rand"
 )
 
 // NewSelector returns an initialised round robin selector

selector/roundrobin/roundrobin_test.go

@@ -3,7 +3,7 @@ package roundrobin
 import (
 	"testing"
 
-	"go.unistack.org/micro/v3/selector"
+	"go.unistack.org/micro/v4/selector"
 )
 
 func TestRoundRobin(t *testing.T) {

server/errors.go

@@ -1,6 +1,6 @@
 package server
 
-import "go.unistack.org/micro/v3/errors"
+import "go.unistack.org/micro/v4/errors"
 
 type Error struct {
 	id string

server/errors_test.go

@@ -3,7 +3,7 @@ package server
 import (
 	"testing"
 
-	"go.unistack.org/micro/v3/errors"
+	"go.unistack.org/micro/v4/errors"
 )
 
 func TestError(t *testing.T) {

server/noop.go

@@ -9,16 +9,16 @@ import (
 	"sync"
 	"time"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/errors"
+	"go.unistack.org/micro/v4/errors"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	maddr "go.unistack.org/micro/v3/util/addr"
+	maddr "go.unistack.org/micro/v4/util/addr"
-	mnet "go.unistack.org/micro/v3/util/net"
+	mnet "go.unistack.org/micro/v4/util/net"
-	"go.unistack.org/micro/v3/util/rand"
+	"go.unistack.org/micro/v4/util/rand"
 )
 
 // DefaultCodecs will be used to encode/decode

server/noop_test.go

@@ -5,12 +5,12 @@ import (
 	"fmt"
 	"testing"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/server"
+	"go.unistack.org/micro/v4/server"
 )
 
 type TestHandler struct {

server/options.go

@@ -7,16 +7,16 @@ import (
 	"sync"
 	"time"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	msync "go.unistack.org/micro/v3/sync"
+	msync "go.unistack.org/micro/v4/sync"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 // Option func

server/registry.go

@@ -4,10 +4,10 @@ import (
 	"net"
 	"time"
 
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/util/addr"
+	"go.unistack.org/micro/v4/util/addr"
-	"go.unistack.org/micro/v3/util/backoff"
+	"go.unistack.org/micro/v4/util/backoff"
 )
 
 var (

server/server.go

@@ -5,8 +5,8 @@ import (
 	"context"
 	"time"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
 )
 
 // DefaultServer default server

service.go

@@ -9,17 +9,17 @@ import (
 
 	"github.com/KimMachineGun/automemlimit/memlimit"
 	"go.uber.org/automaxprocs/maxprocs"
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/config"
+	"go.unistack.org/micro/v4/config"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	"go.unistack.org/micro/v3/server"
+	"go.unistack.org/micro/v4/server"
-	"go.unistack.org/micro/v3/store"
+	"go.unistack.org/micro/v4/store"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
-	utildns "go.unistack.org/micro/v3/util/dns"
+	utildns "go.unistack.org/micro/v4/util/dns"
 )
 
 func init() {

service_test.go

@@ -5,16 +5,16 @@ import (
 	"reflect"
 	"testing"
 
-	"go.unistack.org/micro/v3/broker"
+	"go.unistack.org/micro/v4/broker"
-	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v4/client"
-	"go.unistack.org/micro/v3/config"
+	"go.unistack.org/micro/v4/config"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	"go.unistack.org/micro/v3/server"
+	"go.unistack.org/micro/v4/server"
-	"go.unistack.org/micro/v3/store"
+	"go.unistack.org/micro/v4/store"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 func TestClient(t *testing.T) {

store/memory/memory.go

@@ -8,8 +8,8 @@ import (
 	"time"
 
 	cache "github.com/patrickmn/go-cache"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/store"
+	"go.unistack.org/micro/v4/store"
 )
 
 // NewStore returns a memory store

store/memory/memory_test.go

@@ -5,7 +5,7 @@ import (
 	"testing"
 	"time"
 
-	"go.unistack.org/micro/v3/store"
+	"go.unistack.org/micro/v4/store"
 )
 
 type testHook struct {

store/noop.go

@@ -5,8 +5,8 @@ import (
 	"sync"
 	"sync/atomic"
 
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 var _ Store = (*noopStore)(nil)

store/options.go

@@ -5,12 +5,12 @@ import (
 	"crypto/tls"
 	"time"
 
-	"go.unistack.org/micro/v3/codec"
+	"go.unistack.org/micro/v4/codec"
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/options"
+	"go.unistack.org/micro/v4/options"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options contains configuration for the Store

sync/options.go

@@ -3,9 +3,9 @@ package sync
 import (
 	"time"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 // Options holds the sync options

tracer/memory/memory.go

@@ -4,8 +4,8 @@ import (
 	"context"
 	"time"
 
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 var _ tracer.Tracer = (*Tracer)(nil)

tracer/memory/memory_test.go

@@ -7,9 +7,9 @@ import (
 	"strings"
 	"testing"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
-	"go.unistack.org/micro/v3/logger/slog"
+	"go.unistack.org/micro/v4/logger/slog"
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 func TestLoggerWithTracer(t *testing.T) {

tracer/noop.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"time"
 
-	"go.unistack.org/micro/v3/util/id"
+	"go.unistack.org/micro/v4/util/id"
 )
 
 var _ Tracer = (*noopTracer)(nil)

tracer/options.go

@@ -3,7 +3,7 @@ package tracer
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
 )
 
 type SpanStatus int

tracer/tracer.go

@@ -4,7 +4,7 @@ package tracer
 import (
 	"context"
 
-	"go.unistack.org/micro/v3/logger"
+	"go.unistack.org/micro/v4/logger"
 )
 
 var (

util/buf/buf.go

@@ -1,27 +0,0 @@
-package buf
-
-import (
-	"bytes"
-	"io"
-)
-
-var _ io.Closer = &Buffer{}
-
-// Buffer bytes.Buffer wrapper to satisfie io.Closer interface
-type Buffer struct {
-	*bytes.Buffer
-}
-
-// Close reset buffer contents
-func (b *Buffer) Close() error {
-	b.Buffer.Reset()
-	return nil
-}
-
-// New creates new buffer that satisfies Closer interface
-func New(b *bytes.Buffer) *Buffer {
-	if b == nil {
-		b = bytes.NewBuffer(nil)
-	}
-	return &Buffer{b}
-}

util/buffer/buffer.go

@@ -0,0 +1,85 @@
+package buffer
+
+import (
+	"io"
+	"sync"
+	"time"
+)
+
+var _ io.WriteCloser = (*DelayedBuffer)(nil)
+
+// DelayedBuffer is the buffer that holds items until either the buffer filled or a specified time limit is reached
+type DelayedBuffer struct {
+	mu        sync.Mutex
+	maxWait   time.Duration
+	flushTime time.Time
+	buffer    chan []byte
+	ticker    *time.Ticker
+	w         io.Writer
+	err       error
+}
+
+func NewDelayedBuffer(size int, maxWait time.Duration, w io.Writer) *DelayedBuffer {
+	b := &DelayedBuffer{
+		buffer:    make(chan []byte, size),
+		ticker:    time.NewTicker(maxWait),
+		w:         w,
+		flushTime: time.Now(),
+		maxWait:   maxWait,
+	}
+	b.loop()
+	return b
+}
+
+func (b *DelayedBuffer) loop() {
+	go func() {
+		for range b.ticker.C {
+			b.mu.Lock()
+			if time.Since(b.flushTime) > b.maxWait {
+				b.flush()
+			}
+			b.mu.Unlock()
+		}
+	}()
+}
+
+func (b *DelayedBuffer) flush() {
+	bufLen := len(b.buffer)
+	if bufLen > 0 {
+		tmp := make([][]byte, bufLen)
+		for i := 0; i < bufLen; i++ {
+			tmp[i] = <-b.buffer
+		}
+		for _, t := range tmp {
+			_, b.err = b.w.Write(t)
+		}
+		b.flushTime = time.Now()
+	}
+}
+
+func (b *DelayedBuffer) Put(items ...[]byte) {
+	b.mu.Lock()
+	for _, item := range items {
+		select {
+		case b.buffer <- item:
+		default:
+			b.flush()
+			b.buffer <- item
+		}
+	}
+	b.mu.Unlock()
+}
+
+func (b *DelayedBuffer) Close() error {
+	b.mu.Lock()
+	b.flush()
+	close(b.buffer)
+	b.ticker.Stop()
+	b.mu.Unlock()
+	return b.err
+}
+
+func (b *DelayedBuffer) Write(data []byte) (int, error) {
+	b.Put(data)
+	return len(data), b.err
+}

util/buffer/buffer_test.go

@@ -0,0 +1,22 @@
+package buffer
+
+import (
+	"bytes"
+	"testing"
+	"time"
+)
+
+func TestTimedBuffer(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	b := NewDelayedBuffer(100, 300*time.Millisecond, buf)
+	for i := 0; i < 100; i++ {
+		_, _ = b.Write([]byte(`test`))
+	}
+	if buf.Len() != 0 {
+		t.Fatal("delayed write not worked")
+	}
+	time.Sleep(400 * time.Millisecond)
+	if buf.Len() == 0 {
+		t.Fatal("delayed write not worked")
+	}
+}

util/dns/cache.go

@@ -7,8 +7,8 @@ import (
 	"sync"
 	"time"
 
-	"go.unistack.org/micro/v3/meter"
+	"go.unistack.org/micro/v4/meter"
-	"go.unistack.org/micro/v3/semconv"
+	"go.unistack.org/micro/v4/semconv"
 )
 
 // DialFunc is a [net.Resolver.Dial] function.

util/grpc/tracer.go

@@ -8,7 +8,7 @@ import (
 	"sync/atomic"
 	"time"
 
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 	grpc_codes "google.golang.org/grpc/codes"
 	"google.golang.org/grpc/peer"
 	"google.golang.org/grpc/stats"

util/http/clienttracer.go

@@ -23,7 +23,7 @@ import (
 	"strings"
 	"sync"
 
-	"go.unistack.org/micro/v3/tracer"
+	"go.unistack.org/micro/v4/tracer"
 )
 
 const (

util/http/http.go

@@ -8,8 +8,8 @@ import (
 	"net/http"
 	"strings"
 
-	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v4/metadata"
-	"go.unistack.org/micro/v3/selector/random"
+	"go.unistack.org/micro/v4/selector/random"
 )
 
 // Write sets the status and body on a http ResponseWriter

util/http/http_test.go

@@ -9,10 +9,10 @@ import (
 	"net/http"
 	"testing"
 
-	"go.unistack.org/micro/v3/register"
+	"go.unistack.org/micro/v4/register"
-	"go.unistack.org/micro/v3/register/memory"
+	"go.unistack.org/micro/v4/register/memory"
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	regRouter "go.unistack.org/micro/v3/router/register"
+	regRouter "go.unistack.org/micro/v4/router/register"
 )
 
 func TestRoundTripper(t *testing.T) {

util/http/options.go

@@ -1,6 +1,6 @@
 package http
 
-import "go.unistack.org/micro/v3/router"
+import "go.unistack.org/micro/v4/router"
 
 // Options struct
 type Options struct {

util/http/roundtripper.go

@@ -4,8 +4,8 @@ import (
 	"errors"
 	"net/http"
 
-	"go.unistack.org/micro/v3/router"
+	"go.unistack.org/micro/v4/router"
-	"go.unistack.org/micro/v3/selector"
+	"go.unistack.org/micro/v4/selector"
 )
 
 type roundTripper struct {

util/jitter/random.go

@@ -4,7 +4,7 @@ package jitter
 import (
 	"time"
 
-	"go.unistack.org/micro/v3/util/rand"
+	"go.unistack.org/micro/v4/util/rand"
 )
 
 // Random returns a random time to jitter with max cap specified

util/jitter/ticker.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"time"
 
-	"go.unistack.org/micro/v3/util/rand"
+	"go.unistack.org/micro/v4/util/rand"
 )
 
 // Ticker is similar to time.Ticker but ticks at random intervals between

util/reflect/struct_test.go

@@ -6,7 +6,7 @@ import (
 	"testing"
 	"time"
 
-	rutil "go.unistack.org/micro/v3/util/reflect"
+	rutil "go.unistack.org/micro/v4/util/reflect"
 )
 
 func TestStructFields(t *testing.T) {