Add admin API to send console log messages (#7784)

Utilized by mc admin console command.

pkg/madmin/api-log.go

@@ -0,0 +1,85 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 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 madmin
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/minio/minio/cmd/logger/message/log"
+)
+
+// LogInfo holds console log messages
+type LogInfo struct {
+	log.Entry
+	NodeName string `json:"node"`
+	Err      error  `json:"-"`
+}
+
+// SendLog returns true if log pertains to node specified in args.
+func (l LogInfo) SendLog(node string) bool {
+	return node == "" || strings.ToLower(node) == strings.ToLower(l.NodeName)
+}
+
+// GetLogs - listen on console log messages.
+func (adm AdminClient) GetLogs(node string, lineCnt int, doneCh <-chan struct{}) <-chan LogInfo {
+	logCh := make(chan LogInfo, 1)
+
+	// Only success, start a routine to start reading line by line.
+	go func(logCh chan<- LogInfo) {
+		defer close(logCh)
+		urlValues := make(url.Values)
+		urlValues.Set("node", node)
+		urlValues.Set("limit", strconv.Itoa(lineCnt))
+		for {
+			reqData := requestData{
+				relPath:     "/v1/log",
+				queryValues: urlValues,
+			}
+			// Execute GET to call log handler
+			resp, err := adm.executeMethod("GET", reqData)
+			if err != nil {
+				closeResponse(resp)
+				return
+			}
+
+			if resp.StatusCode != http.StatusOK {
+				logCh <- LogInfo{Err: httpRespToErrorResponse(resp)}
+				return
+			}
+			dec := json.NewDecoder(resp.Body)
+			for {
+				var info LogInfo
+				if err = dec.Decode(&info); err != nil {
+					break
+				}
+				select {
+				case <-doneCh:
+					return
+				case logCh <- info:
+				}
+			}
+
+		}
+	}(logCh)
+
+	// Returns the log info channel, for caller to start reading from.
+	return logCh
+}

pkg/pubsub/pubsub.go

@@ -40,7 +40,7 @@ func (ps *PubSub) Publish(item interface{}) {
 	defer ps.RUnlock()
 
 	for _, sub := range ps.subs {
-		if sub.filter(item) {
+		if sub.filter == nil || sub.filter(item) {
 			select {
 			case sub.ch <- item:
 			default: