3 files changed, 242 insertions, 0 deletions
diff --git a/pkg/logging/journald_core.go b/pkg/logging/journald_core.go
new file mode 100644
index 0000000..50dd39f
--- /dev/null
+++ b/pkg/logging/journald_core.go
@@ -0,0 +1,85 @@
+package logging
+
+import (
+	"github.com/icinga/icingadb/pkg/utils"
+	"github.com/pkg/errors"
+	"github.com/ssgreg/journald"
+	"go.uber.org/zap/zapcore"
+	"strings"
+	"unicode"
+)
+
+// priorities maps zapcore.Level to journal.Priority.
+var priorities = map[zapcore.Level]journald.Priority{
+	zapcore.DebugLevel:  journald.PriorityDebug,
+	zapcore.InfoLevel:   journald.PriorityInfo,
+	zapcore.WarnLevel:   journald.PriorityWarning,
+	zapcore.ErrorLevel:  journald.PriorityErr,
+	zapcore.FatalLevel:  journald.PriorityCrit,
+	zapcore.PanicLevel:  journald.PriorityCrit,
+	zapcore.DPanicLevel: journald.PriorityCrit,
+}
+
+// NewJournaldCore returns a zapcore.Core that sends log entries to systemd-journald and
+// uses the given identifier as a prefix for structured logging context that is sent as journal fields.
+func NewJournaldCore(identifier string, enab zapcore.LevelEnabler) zapcore.Core {
+	return &journaldCore{
+		LevelEnabler: enab,
+		identifier:   identifier,
+		identifierU:  strings.ToUpper(identifier),
+	}
+}
+
+type journaldCore struct {
+	zapcore.LevelEnabler
+	context     []zapcore.Field
+	identifier  string
+	identifierU string
+}
+
+func (c *journaldCore) Check(ent zapcore.Entry, ce *zapcore.CheckedEntry) *zapcore.CheckedEntry {
+	if c.Enabled(ent.Level) {
+		return ce.AddCore(ent, c)
+	}
+
+	return ce
+}
+
+func (c *journaldCore) Sync() error {
+	return nil
+}
+
+func (c *journaldCore) With(fields []zapcore.Field) zapcore.Core {
+	cc := *c
+	cc.context = append(cc.context[:len(cc.context):len(cc.context)], fields...)
+
+	return &cc
+}
+
+func (c *journaldCore) Write(ent zapcore.Entry, fields []zapcore.Field) error {
+	pri, ok := priorities[ent.Level]
+	if !ok {
+		return errors.Errorf("unknown log level %q", ent.Level)
+	}
+
+	enc := zapcore.NewMapObjectEncoder()
+	c.addFields(enc, fields)
+	c.addFields(enc, c.context)
+	enc.Fields["SYSLOG_IDENTIFIER"] = c.identifier
+
+	message := ent.Message
+	if ent.LoggerName != c.identifier {
+		message = ent.LoggerName + ": " + message
+	}
+
+	return journald.Send(message, pri, enc.Fields)
+}
+
+func (c *journaldCore) addFields(enc zapcore.ObjectEncoder, fields []zapcore.Field) {
+	for _, field := range fields {
+		field.Key = c.identifierU +
+			"_" +
+			utils.ConvertCamelCase(field.Key, unicode.UpperCase, '_')
+		field.AddTo(enc)
+	}
+}
diff --git a/pkg/logging/logger.go b/pkg/logging/logger.go
new file mode 100644
index 0000000..490445e
--- /dev/null
+++ b/pkg/logging/logger.go
@@ -0,0 +1,26 @@
+package logging
+
+import (
+	"go.uber.org/zap"
+	"time"
+)
+
+// Logger wraps zap.SugaredLogger and
+// allows to get the interval for periodic logging.
+type Logger struct {
+	*zap.SugaredLogger
+	interval time.Duration
+}
+
+// NewLogger returns a new Logger.
+func NewLogger(base *zap.SugaredLogger, interval time.Duration) *Logger {
+	return &Logger{
+		SugaredLogger: base,
+		interval:      interval,
+	}
+}
+
+// Interval returns the interval for periodic logging.
+func (l *Logger) Interval() time.Duration {
+	return l.interval
+}
diff --git a/pkg/logging/logging.go b/pkg/logging/logging.go
new file mode 100644
index 0000000..e310695
--- /dev/null
+++ b/pkg/logging/logging.go
@@ -0,0 +1,131 @@
+package logging
+
+import (
+	"fmt"
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+	"os"
+	"sync"
+	"time"
+)
+
+const (
+	CONSOLE = "console"
+	JOURNAL = "systemd-journald"
+)
+
+// defaultEncConfig defines the default zapcore.EncoderConfig for the logging package.
+var defaultEncConfig = zapcore.EncoderConfig{
+	TimeKey:        "ts",
+	LevelKey:       "level",
+	NameKey:        "logger",
+	CallerKey:      "caller",
+	MessageKey:     "msg",
+	StacktraceKey:  "stacktrace",
+	LineEnding:     zapcore.DefaultLineEnding,
+	EncodeLevel:    zapcore.CapitalLevelEncoder,
+	EncodeTime:     zapcore.ISO8601TimeEncoder,
+	EncodeDuration: zapcore.StringDurationEncoder,
+	EncodeCaller:   zapcore.ShortCallerEncoder,
+}
+
+// Options define child loggers with their desired log level.
+type Options map[string]zapcore.Level
+
+// Logging implements access to a default logger and named child loggers.
+// Log levels can be configured per named child via Options which, if not configured,
+// fall back on a default log level.
+// Logs either to the console or to systemd-journald.
+type Logging struct {
+	logger    *Logger
+	output    string
+	verbosity zap.AtomicLevel
+	interval  time.Duration
+
+	// coreFactory creates zapcore.Core based on the log level and the log output.
+	coreFactory func(zap.AtomicLevel) zapcore.Core
+
+	mu      sync.Mutex
+	loggers map[string]*Logger
+
+	options Options
+}
+
+// NewLogging takes the name and log level for the default logger,
+// output where log messages are written to,
+// options having log levels for named child loggers
+// and returns a new Logging.
+func NewLogging(name string, level zapcore.Level, output string, options Options, interval time.Duration) (*Logging, error) {
+	verbosity := zap.NewAtomicLevelAt(level)
+
+	var coreFactory func(zap.AtomicLevel) zapcore.Core
+	switch output {
+	case CONSOLE:
+		enc := zapcore.NewConsoleEncoder(defaultEncConfig)
+		ws := zapcore.Lock(os.Stderr)
+		coreFactory = func(verbosity zap.AtomicLevel) zapcore.Core {
+			return zapcore.NewCore(enc, ws, verbosity)
+		}
+	case JOURNAL:
+		coreFactory = func(verbosity zap.AtomicLevel) zapcore.Core {
+			return NewJournaldCore(name, verbosity)
+		}
+	default:
+		return nil, invalidOutput(output)
+	}
+
+	logger := NewLogger(zap.New(coreFactory(verbosity)).Named(name).Sugar(), interval)
+
+	return &Logging{
+			logger:      logger,
+			output:      output,
+			verbosity:   verbosity,
+			interval:    interval,
+			coreFactory: coreFactory,
+			loggers:     make(map[string]*Logger),
+			options:     options,
+		},
+		nil
+}
+
+// GetChildLogger returns a named child logger.
+// Log levels for named child loggers are obtained from the logging options and, if not found,
+// set to the default log level.
+func (l *Logging) GetChildLogger(name string) *Logger {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	if logger, ok := l.loggers[name]; ok {
+		return logger
+	}
+
+	var verbosity zap.AtomicLevel
+	if level, found := l.options[name]; found {
+		verbosity = zap.NewAtomicLevelAt(level)
+	} else {
+		verbosity = l.verbosity
+	}
+
+	logger := NewLogger(zap.New(l.coreFactory(verbosity)).Named(name).Sugar(), l.interval)
+	l.loggers[name] = logger
+
+	return logger
+}
+
+// GetLogger returns the default logger.
+func (l *Logging) GetLogger() *Logger {
+	return l.logger
+}
+
+// AssertOutput returns an error if output is not a valid logger output.
+func AssertOutput(o string) error {
+	if o == CONSOLE || o == JOURNAL {
+		return nil
+	}
+
+	return invalidOutput(o)
+}
+
+func invalidOutput(o string) error {
+	return fmt.Errorf("%s is not a valid logger output. Must be either %q or %q", o, CONSOLE, JOURNAL)
+}