make notification as separate package (#5294)

* Remove old notification files

* Add net package

* Add event package

* Modify minio to take new notification system

pkg/event/target/httpclient.go

@@ -0,0 +1,141 @@
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package target
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"sync/atomic"
+	"time"
+
+	"github.com/minio/minio/pkg/event"
+	xnet "github.com/minio/minio/pkg/net"
+	"github.com/skyrings/skyring-common/tools/uuid"
+)
+
+// HTTPClientTarget - HTTP client target.
+type HTTPClientTarget struct {
+	id        event.TargetID
+	w         http.ResponseWriter
+	eventCh   chan []byte
+	DoneCh    chan struct{}
+	stopCh    chan struct{}
+	isStopped uint32
+	isRunning uint32
+}
+
+// ID - returns target ID.
+func (target HTTPClientTarget) ID() event.TargetID {
+	return target.id
+}
+
+func (target *HTTPClientTarget) start() {
+	go func() {
+		defer func() {
+			atomic.AddUint32(&target.isRunning, 1)
+
+			// Close DoneCh to indicate we are done.
+			close(target.DoneCh)
+		}()
+
+		write := func(event []byte) error {
+			if _, err := target.w.Write(event); err != nil {
+				return err
+			}
+
+			target.w.(http.Flusher).Flush()
+			return nil
+		}
+
+		for {
+			keepAliveTicker := time.NewTicker(500 * time.Millisecond)
+			select {
+			case <-target.stopCh:
+				// We are asked to stop.
+				return
+			case event, ok := <-target.eventCh:
+				if !ok {
+					// Got read error.  Exit the goroutine.
+					return
+				}
+				if err := write(event); err != nil {
+					// Got write error to the client.  Exit the goroutine.
+					return
+				}
+			case <-keepAliveTicker.C:
+				if err := write([]byte(" ")); err != nil {
+					// Got write error to the client.  Exit the goroutine.
+					return
+				}
+			}
+		}
+	}()
+}
+
+// Send - sends event to HTTP client.
+func (target *HTTPClientTarget) Send(eventData event.Event) error {
+	if atomic.LoadUint32(&target.isRunning) != 0 {
+		return errors.New("closed http connection")
+	}
+
+	data, err := json.Marshal(struct{ Records []event.Event }{[]event.Event{eventData}})
+	if err != nil {
+		return err
+	}
+	data = append(data, byte('\n'))
+
+	select {
+	case target.eventCh <- data:
+		return nil
+	case <-target.DoneCh:
+		return errors.New("error in sending event")
+	}
+}
+
+// Close - closes underneath goroutine.
+func (target *HTTPClientTarget) Close() error {
+	atomic.AddUint32(&target.isStopped, 1)
+	if atomic.LoadUint32(&target.isStopped) == 1 {
+		close(target.stopCh)
+	}
+
+	return nil
+}
+
+func mustGetNewUUID() string {
+	uuid, err := uuid.New()
+	if err != nil {
+		panic(fmt.Sprintf("%s. Unable to generate random UUID", err))
+	}
+
+	return uuid.String()
+}
+
+// NewHTTPClientTarget - creates new HTTP client target.
+func NewHTTPClientTarget(host xnet.Host, w http.ResponseWriter) *HTTPClientTarget {
+	c := &HTTPClientTarget{
+		id:      event.TargetID{"httpclient" + "+" + mustGetNewUUID() + "+" + host.Name, host.Port.String()},
+		w:       w,
+		eventCh: make(chan []byte),
+		DoneCh:  make(chan struct{}),
+		stopCh:  make(chan struct{}),
+	}
+	c.start()
+	return c
+}