1 files changed, 85 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)
+	}
+}