move cfg to loggers + refactor + log fn wrappers

1. Instead of maintaining a global config, each specialized logger
now stores its config.
2. Refactored logInterface to elektronLogger.
3. Refactored loggerImpl to baseElektronLogger to be consistent with
the rest of the code base.
4. Wrapped elektronLogger#Log(...) and elektronLogf(...) so that we
do not have to use the instance of elektronLogger everytime we want
to log. Instead, we just do logging.Log(...) or logging.Logf(...).
5. Wrapped elektronLogger#WithFields(...) and
elektronLogger#WithField(...).
6. Refactored codebase to adhere to the changes.

logging/logger.go

@@ -1,6 +1,7 @@
 package logging
 
 import (
+	"github.com/pkg/errors"
 	"os"
 	"strings"
 	"time"
@@ -9,14 +10,75 @@ import (
 	. "github.com/spdfg/elektron/logging/types"
 )
 
-var config LoggerConfig
+// var config LoggerConfig
 var formatter ElektronFormatter
-var ElektronLogger *loggerImpl
+var elektronLoggerInstance elektronLogger
 
-func BuildLogger(prefix string, logConfigFilename string) {
+type elektronLogger interface {
+	setNext(next elektronLogger)
+	isEnabled() bool
+	Log(logType int, level log.Level, message string)
+	Logf(logType int, level log.Level, msgFmtString string, args ...interface{})
+	WithFields(logData log.Fields) elektronLogger
+	WithField(key string, value string) elektronLogger
+}
 
-	// Read configuration from yaml.
-	config.GetConfig(logConfigFilename)
+type baseLogData struct {
+	data log.Fields
+}
+
+type baseElektronLogger struct {
+	*baseLogData
+
+	config struct {
+		Enabled           bool
+		FilenameExtension string
+		AllowOnConsole    bool
+	}
+
+	logType int
+	logFile *os.File
+	next    elektronLogger
+	logger  *log.Logger
+	logDir  *logDirectory
+}
+
+func (l baseElektronLogger) isEnabled() bool {
+	return l.config.Enabled
+}
+
+func (l *baseElektronLogger) WithFields(logData log.Fields) elektronLogger {
+	l.data = logData
+	return l
+}
+
+func (l *baseElektronLogger) WithField(key string, value string) elektronLogger {
+	l.data[key] = value
+	return l
+}
+
+func (l *baseElektronLogger) setNext(next elektronLogger) {
+	l.next = next
+}
+
+func (l baseElektronLogger) Log(logType int, level log.Level, message string) {
+	if l.next != nil {
+		l.next.Log(logType, level, message)
+	}
+}
+
+func (l baseElektronLogger) Logf(logType int, level log.Level, msgFmtString string, args ...interface{}) {
+	if l.next != nil {
+		l.next.Logf(logType, level, msgFmtString, args...)
+	}
+}
+
+func (l *baseElektronLogger) resetFields() {
+	l.data = nil
+	l.data = log.Fields{}
+}
+
+func BuildLogger(prefix string, logConfigFilename string) error {
 
 	// Create the log directory.
 	startTime := time.Now()
@@ -35,20 +97,44 @@ func BuildLogger(prefix string, logConfigFilename string) {
 
 	// Create a chain of loggers.
 	b := &baseLogData{data: log.Fields{}}
-	head := &loggerImpl{baseLogData: b}
-	cLog := NewConsoleLogger(b, CONSOLE, prefix, logger, logDir)
-	pLog := NewPCPLogger(b, PCP, prefix, logger, logDir)
-	schedTraceLog := NewSchedTraceLogger(b, SCHED_TRACE, prefix, logger, logDir)
-	spsLog := NewSchedPolicySwitchLogger(b, SPS, prefix, logger, logDir)
-	schedWindowLog := NewSchedWindowLogger(b, SCHED_WINDOW, prefix, logger, logDir)
-	tskDistLog := NewClsfnTaskDistrOverheadLogger(b, CLSFN_TASKDISTR_OVERHEAD, prefix, logger, logDir)
+	head := &baseElektronLogger{baseLogData: b}
 
-	head.setNext(cLog)
-	cLog.setNext(pLog)
-	pLog.setNext(schedTraceLog)
-	schedTraceLog.setNext(spsLog)
-	spsLog.setNext(schedWindowLog)
-	schedWindowLog.setNext(tskDistLog)
+	// Read configuration from yaml.
+	if config, err := GetConfig(logConfigFilename); err != nil {
+		return errors.Wrap(err, "Failed to build logger")
+	} else {
+		cLog := NewConsoleLogger(config, b, CONSOLE, prefix, logger, logDir)
+		pLog := NewPCPLogger(config, b, PCP, prefix, logger, logDir)
+		schedTraceLog := NewSchedTraceLogger(config, b, SCHED_TRACE, prefix, logger, logDir)
+		spsLog := NewSchedPolicySwitchLogger(config, b, SPS, prefix, logger, logDir)
+		schedWindowLog := NewSchedWindowLogger(config, b, SCHED_WINDOW, prefix, logger, logDir)
+		tskDistLog := NewClsfnTaskDistrOverheadLogger(config, b, CLSFN_TASKDISTR_OVERHEAD, prefix, logger, logDir)
 
-	ElektronLogger = head
+		head.setNext(cLog)
+		cLog.setNext(pLog)
+		pLog.setNext(schedTraceLog)
+		schedTraceLog.setNext(spsLog)
+		spsLog.setNext(schedWindowLog)
+		schedWindowLog.setNext(tskDistLog)
+
+	}
+
+	elektronLoggerInstance = head
+	return nil
+}
+
+func Log(logType int, level log.Level, message string) {
+	elektronLoggerInstance.Log(logType, level, message)
+}
+
+func Logf(logType int, level log.Level, msgFmtString string, args ...interface{}) {
+	elektronLoggerInstance.Logf(logType, level, msgFmtString, args...)
+}
+
+func WithFields(logData log.Fields) elektronLogger {
+	return elektronLoggerInstance.WithFields(logData)
+}
+
+func WithField(key string, value string) elektronLogger {
+	return elektronLoggerInstance.WithField(key, value)
 }