Make priority queue lambda function return error over a channel

pkg/server/api/logging-handlers.go

@@ -0,0 +1,118 @@
+/*
+ * Minimalist Object Storage, (C) 2015 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 api
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/dustin/go-humanize"
+	"github.com/minio/minio/pkg/iodine"
+	"github.com/minio/minio/pkg/utils/log"
+)
+
+type logHandler struct {
+	handler http.Handler
+	logger  chan<- []byte
+}
+
+// logMessage is a serializable json log message
+type logMessage struct {
+	StartTime     time.Time
+	Duration      time.Duration
+	StatusMessage string // human readable http status message
+	ContentLength string // human readable content length
+
+	// HTTP detailed message
+	HTTP struct {
+		ResponseHeaders http.Header
+		Request         *http.Request
+	}
+}
+
+// logWriter is used to capture status for log messages
+type logWriter struct {
+	responseWriter http.ResponseWriter
+	logMessage     *logMessage
+}
+
+// WriteHeader writes headers and stores status in LogMessage
+func (w *logWriter) WriteHeader(status int) {
+	w.logMessage.StatusMessage = http.StatusText(status)
+	w.responseWriter.WriteHeader(status)
+}
+
+// Header Dummy wrapper for LogWriter
+func (w *logWriter) Header() http.Header {
+	return w.responseWriter.Header()
+}
+
+// Write Dummy wrapper for LogWriter
+func (w *logWriter) Write(data []byte) (int, error) {
+	return w.responseWriter.Write(data)
+}
+
+func (h *logHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	logMessage := &logMessage{
+		StartTime: time.Now().UTC(),
+	}
+	logWriter := &logWriter{responseWriter: w, logMessage: logMessage}
+	h.handler.ServeHTTP(logWriter, req)
+	h.logger <- getLogMessage(logMessage, w, req)
+}
+
+func getLogMessage(logMessage *logMessage, w http.ResponseWriter, req *http.Request) []byte {
+	// store lower level details
+	logMessage.HTTP.ResponseHeaders = w.Header()
+	logMessage.HTTP.Request = req
+
+	// humanize content-length to be printed in logs
+	contentLength, _ := strconv.Atoi(logMessage.HTTP.ResponseHeaders.Get("Content-Length"))
+	logMessage.ContentLength = humanize.IBytes(uint64(contentLength))
+	logMessage.Duration = time.Now().UTC().Sub(logMessage.StartTime)
+	js, _ := json.Marshal(logMessage)
+	js = append(js, byte('\n')) // append a new line
+	return js
+}
+
+// LoggingHandler logs requests
+func LoggingHandler(h http.Handler) http.Handler {
+	logger, _ := fileLogger("access.log")
+	return &logHandler{handler: h, logger: logger}
+}
+
+// fileLogger returns a channel that is used to write to the logger
+func fileLogger(filename string) (chan<- []byte, error) {
+	ch := make(chan []byte)
+	file, err := os.OpenFile(filename, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
+	if err != nil {
+		return nil, iodine.New(err, map[string]string{"logfile": filename})
+	}
+	go func() {
+		for message := range ch {
+			if _, err := io.Copy(file, bytes.NewBuffer(message)); err != nil {
+				log.Println(iodine.New(err, nil))
+			}
+		}
+	}()
+	return ch, nil
+}