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

Utilized by mc admin console command.

cmd/consolelogger.go

@@ -0,0 +1,128 @@
+/*
+ * 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 cmd
+
+import (
+	ring "container/ring"
+	"context"
+
+	"github.com/minio/minio/cmd/logger"
+	"github.com/minio/minio/cmd/logger/message/log"
+	"github.com/minio/minio/cmd/logger/target/console"
+	"github.com/minio/minio/pkg/madmin"
+	xnet "github.com/minio/minio/pkg/net"
+	"github.com/minio/minio/pkg/pubsub"
+)
+
+// number of log messages to buffer
+const defaultLogBufferCount = 10000
+
+//HTTPConsoleLoggerSys holds global console logger state
+type HTTPConsoleLoggerSys struct {
+	pubsub   *pubsub.PubSub
+	console  *console.Target
+	nodeName string
+	logBuf   *ring.Ring
+}
+
+// NewConsoleLogger - creates new HTTPConsoleLoggerSys with all nodes subscribed to
+// the console logging pub sub system
+func NewConsoleLogger(ctx context.Context, endpoints EndpointList) *HTTPConsoleLoggerSys {
+	host, err := xnet.ParseHost(GetLocalPeer(globalEndpoints))
+	if err != nil {
+		logger.FatalIf(err, "Unable to start console logging subsystem")
+	}
+	var nodeName string
+	if globalIsDistXL {
+		nodeName = host.Name
+	}
+	ps := pubsub.New()
+	return &HTTPConsoleLoggerSys{
+		ps, nil, nodeName, ring.New(defaultLogBufferCount),
+	}
+}
+
+// HasLogListeners returns true if console log listeners are registered
+// for this node or peers
+func (sys *HTTPConsoleLoggerSys) HasLogListeners() bool {
+	return sys != nil && sys.pubsub.HasSubscribers()
+}
+
+// Subscribe starts console logging for this node.
+func (sys *HTTPConsoleLoggerSys) Subscribe(subCh chan interface{}, doneCh chan struct{}, node string, last int, filter func(entry interface{}) bool) {
+	// Enable console logging for remote client even if local console logging is disabled in the config.
+	if !globalServerConfig.Logger.Console.Enabled && !sys.pubsub.HasSubscribers() {
+		logger.AddTarget(globalConsoleSys.Console())
+	}
+
+	cnt := 0
+	// by default send all console logs in the ring buffer unless node or limit query parameters
+	// are set.
+	var lastN []madmin.LogInfo
+	if last > defaultLogBufferCount || last <= 0 {
+		last = defaultLogBufferCount
+	}
+
+	lastN = make([]madmin.LogInfo, last)
+	r := sys.logBuf
+	r.Do(func(p interface{}) {
+		if p != nil && (p.(madmin.LogInfo)).SendLog(node) {
+			lastN[cnt%last] = p.(madmin.LogInfo)
+			cnt++
+		}
+	})
+	// send last n console log messages in order filtered by node
+	if cnt > 0 {
+		for i := 0; i < last; i++ {
+			entry := lastN[(cnt+i)%last]
+			if (entry == madmin.LogInfo{}) {
+				continue
+			}
+			select {
+			case subCh <- entry:
+			case <-doneCh:
+				return
+			}
+		}
+	}
+	sys.pubsub.Subscribe(subCh, doneCh, filter)
+}
+
+// Console returns a  console target
+func (sys *HTTPConsoleLoggerSys) Console() *HTTPConsoleLoggerSys {
+	if sys.console == nil {
+		sys.console = console.New()
+	}
+	return sys
+}
+
+// Send log message 'e' to console and publish to console
+// log pubsub system
+func (sys *HTTPConsoleLoggerSys) Send(e interface{}) error {
+	lg := madmin.LogInfo{}
+	lg.Entry = e.(log.Entry)
+	lg.NodeName = sys.nodeName
+	sys.pubsub.Publish(lg)
+	// add log to ring buffer
+	sys.logBuf.Value = lg
+	sys.logBuf = sys.logBuf.Next()
+
+	if globalServerConfig.Logger.Console.Enabled {
+		return sys.console.Send(e)
+	}
+	return nil
+}