pkg/newlog: suppress syslog/kernel logging using the log level settings

Patch uses log level settings for the syslog and kernel introduced
in the previous patch in pillar. Syslog /dev/log and kernel /dev/kmsg
ring buffer are always populated with the log messages regardless
of specified log level. The task of newlogd filter out log messages
which log levels higher than specified in configuration settings.

The default log level set is "info".

Signed-off-by: Roman Penyaev <r.peniaev@gmail.com>

pkg/newlog/cmd/newlogd.go

@@ -19,6 +19,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync/atomic"
 	"syscall"
 	"time"
 	"unicode"
@@ -103,8 +104,12 @@ var (
 
 	//domainUUID
 	domainUUID *base.LockedStringMap // App log, from domain-id to appDomain
-	// syslog/kmsg priority string definition
-	priorityStr = [8]string{"emerg", "alert", "crit", "err", "warning", "notice", "info", "debug"}
+	// Default log levels for some subsystems. Variables are updated and used
+	// from different goroutines, so in order to push the changes out of the
+	// goroutines local caches and correctly observe changed values in another
+	// goroutine sync/atomic synchronization is used. You've been warned.
+	syslogPrio = types.SyslogKernelLogLevelNum[types.SyslogKernelDefaultLogLevel]
+	kernelPrio = types.SyslogKernelLogLevelNum[types.SyslogKernelDefaultLogLevel]
 )
 
 // for app Domain-ID mapping into UUID and DisplayName
@@ -154,6 +159,16 @@ type devMeta struct {
 	curPart  string
 }
 
+// parse log level string
+func parseLogLevel(loglevel string) uint32 {
+	prio, ok := types.SyslogKernelLogLevelNum[loglevel]
+	if !ok {
+		prio = types.SyslogKernelLogLevelNum[types.SyslogKernelDefaultLogLevel]
+	}
+
+	return prio
+}
+
 // newlogd program
 func main() {
 	restartPtr := flag.Bool("r", false, "Restart")
@@ -499,10 +514,27 @@ func handleGlobalConfigImp(ctxArg interface{}, key string, statusArg interface{}
 		if limitGzipFilesMbyts > uint32(persistMbytes/10) {
 			limitGzipFilesMbyts = uint32(persistMbytes / 10)
 		}
+
+		// parse syslog log level
+		syslogPrioStr := gcp.GlobalValueString(types.SyslogLogLevel)
+		atomic.StoreUint32(&syslogPrio, parseLogLevel(syslogPrioStr))
+
+		// parse kernel log level
+		kernelPrioStr := gcp.GlobalValueString(types.KernelLogLevel)
+		atomic.StoreUint32(&kernelPrio, parseLogLevel(kernelPrioStr))
 	}
 	log.Tracef("handleGlobalConfigModify done for %s, fastupload enabled %v", key, enableFastUpload)
 }
 
+func suppressMsg(entry inputEntry, cfgPrio uint32) bool {
+	pri, ok := types.SyslogKernelLogLevelNum[entry.severity]
+	if !ok {
+		pri, _ = types.SyslogKernelLogLevelNum[types.SyslogKernelDefaultLogLevel]
+	}
+
+	return pri > cfgPrio
+}
+
 // getKmessages - goroutine to get from /dev/kmsg
 func getKmessages(loggerChan chan inputEntry) {
 	parser, err := kmsgparser.NewParser()
@@ -515,12 +547,15 @@ func getKmessages(loggerChan chan inputEntry) {
 	for msg := range kmsg {
 		entry := inputEntry{
 			source:    "kernel",
-			severity:  "info",
+			severity:  types.SyslogKernelDefaultLogLevel,
 			content:   msg.Message,
 			timestamp: msg.Timestamp.Format(time.RFC3339Nano),
 		}
 		if msg.Priority >= 0 {
-			entry.severity = priorityStr[msg.Priority%8]
+			entry.severity = types.SyslogKernelLogLevelStr[msg.Priority%8]
+		}
+		if suppressMsg(entry, atomic.LoadUint32(&kernelPrio)) {
+			continue
 		}
 
 		logmetrics.NumKmessages++
@@ -1608,6 +1643,9 @@ func getSyslogMsg(loggerChan chan inputEntry) {
 			log.Error(err)
 			continue
 		}
+		if suppressMsg(entry, atomic.LoadUint32(&syslogPrio)) {
+			continue
+		}
 
 		logmetrics.NumSyslogMessages++
 		logmetrics.DevMetrics.NumInputEvent++
@@ -1652,7 +1690,7 @@ func newMessage(pkt []byte, size int, sysfmt *regexp.Regexp) (inputEntry, error)
 
 	msgReceived := time.Now()
 	p, _ := strconv.ParseInt(string(res[1]), 10, 64)
-	msgPriority = priorityStr[p%8]
+	msgPriority = types.SyslogKernelLogLevelStr[p%8]
 	misc := res[3]
 	// Check for either "hostname tagpid" or "tagpid"
 	a := bytes.SplitN(misc, []byte(" "), 2)