log things

event.go

@@ -11,18 +11,18 @@ import (
 // Event is exported to support the implementation of custom log writers. Most
 // users should not need to handle this type directly.
 type Event struct {
-	// severity of the event
-	Level Level
-
 	// time at which the event occured
 	Time time.Time
 
+	// severity of the event
+	Level Level
+
 	// where the event occurred in the system
 	Path *Path
 
-	// message to be logged
-	Text string
-
 	// key-value pairs to log as extra metadata
 	Tags *Tags
+
+	// message to be logged
+	Text string
 }

line.go

@@ -9,6 +9,10 @@ import (
 	"time"
 )
 
+// LineWriter is an EventWriter that writes one event per line. Event that have
+// multiline messages will have the newlines in their messages replaced with \n
+// sequences. This is the default EventWriter and is designed to be reasonably
+// safe and practical for most users.
 type LineWriter struct {
 	pool sync.Pool
 	out  struct {
@@ -70,6 +74,9 @@ func (l *LineWriter) WriteEvent(e *Event) {
 	l.pool.Put(buf)
 }
 
+// writeTags is a helper for LineWriter's WriteEvent method. writeTags writes
+// tags in the order in which they were added to the list of tags; the oldest
+// tag is always written first.
 func writeTags(buf *bytes.Buffer, tags *Tags) {
 	if tags.parent != nil {
 		writeTags(buf, tags.parent)

log.go

@@ -5,7 +5,6 @@ import (
 )
 
 type Log struct {
-	lvl   Level
 	dw    EventWriter
 	iw    EventWriter
 	ew    EventWriter
@@ -14,20 +13,14 @@ type Log struct {
 	tags  *Tags
 }
 
-type Options struct {
+func NewLog(name string, options ...Option) *Log {
-	Debug EventWriter
+	l := &Log{
-	Info  EventWriter
+		path: NewPath(name),
-	Error EventWriter
 	}
-
+	for _, opt := range options {
-var defaults Options
+		opt.apply(l)
-
-func init() {
-	defaults.Debug = NullWriter{}
 	}
-
+	return l
-func NewLog() *Log {
-	return new(Log)
 }
 
 func format(t string, args ...interface{}) string {
@@ -37,19 +30,104 @@ func format(t string, args ...interface{}) string {
 	return fmt.Sprintf(t, args...)
 }
 
+func (l *Log) event(lvl Level, t string, args ...interface{}) *Event {
+	return &Event{
+		Time:  l.clock.Now(),
+		Level: lvl,
+		Path:  l.path,
+		Tags:  l.tags,
+		Text:  format(t, args...),
+	}
+}
+
 func (l *Log) Debug(t string, args ...interface{}) {
+	if l.dw != nil {
+		l.dw.WriteEvent(l.event(Debug, t, args...))
+	}
 }
 
 func (l *Log) Info(t string, args ...interface{}) {
+	if l.iw != nil {
+		l.iw.WriteEvent(l.event(Info, t, args...))
+	}
 }
 
 func (l *Log) Error(t string, args ...interface{}) {
+	if l.ew != nil {
+		l.ew.WriteEvent(l.event(Error, t, args...))
+	}
 }
 
 func (l *Log) Child(name string) *Log {
-	return l
+	return &Log{
+		dw:    l.dw,
+		iw:    l.iw,
+		ew:    l.ew,
+		path:  l.path.Child(name),
+		clock: l.clock,
+		tags:  l.tags,
+	}
 }
 
-func (l *Log) Tag(key string, value interface{}) *Log {
+// Tag creates a new Tags struct having the given key as its final key, with no
-	return l
+// associated value. All existing keys continue to exist.
+func (l *Log) Tag(key string) *Log {
+	return &Log{
+		dw:    l.dw,
+		iw:    l.iw,
+		ew:    l.ew,
+		path:  l.path,
+		clock: l.clock,
+		tags:  &Tags{key: key, parent: l.tags},
+	}
 }
+
+// TagInt creates a new Tags struct having the given key-value pair as the
+// final key-value pair. All existing key-value pairs continue to exist.
+func (l *Log) TagInt(key string, v int) *Log {
+	return &Log{
+		dw:    l.dw,
+		iw:    l.iw,
+		ew:    l.ew,
+		path:  l.path,
+		clock: l.clock,
+		tags:  &Tags{key: key, value: v, parent: l.tags},
+	}
+}
+
+// TagString creates a new Tags struct having the given key-value pair as the
+// final key-value pair. All existing key-value pairs continue to exist.
+func (l *Log) TagString(key, v string) *Log {
+	return &Log{
+		dw:    l.dw,
+		iw:    l.iw,
+		ew:    l.ew,
+		path:  l.path,
+		clock: l.clock,
+		tags:  &Tags{key: key, value: v, parent: l.tags},
+	}
+}
+
+// TagFloat creates a new Tags struct having the given key-value pair as the
+// final key-value pair. All existing key-value pairs continue to exist.
+func (l *Log) TagFloat(key string, v float64) *Log {
+	return &Log{
+		dw:    l.dw,
+		iw:    l.iw,
+		ew:    l.ew,
+		path:  l.path,
+		clock: l.clock,
+		tags:  &Tags{key: key, value: v, parent: l.tags},
+	}
+}
+
+type Option interface{ apply(*Log) }
+
+type optionFn func(*Log)
+
+func (fn optionFn) apply(l *Log) { fn(l) }
+
+func DebugWriter(w EventWriter) Option { return optionFn(func(l *Log) { l.dw = w }) }
+func InfoWriter(w EventWriter) Option  { return optionFn(func(l *Log) { l.iw = w }) }
+func ErrorWriter(w EventWriter) Option { return optionFn(func(l *Log) { l.ew = w }) }
+func UserClock(c Clock) Option         { return optionFn(func(l *Log) { l.clock = c }) }

tag.go

@@ -13,27 +13,3 @@ type Tags struct {
 	value  interface{}
 	parent *Tags
 }
-
-// Tag creates a new Tags struct having the given key as its final key, with no
-// associated value. All existing keys continue to exist.
-func (t *Tags) Tag(key string) *Tags {
-	return &Tags{key: key, parent: t}
-}
-
-// TagInt creates a new Tags struct having the given key-value pair as the
-// final key-value pair. All existing key-value pairs continue to exist.
-func (t *Tags) TagInt(key string, v int) *Tags {
-	return &Tags{key: key, value: v, parent: t}
-}
-
-// TagString creates a new Tags struct having the given key-value pair as the
-// final key-value pair. All existing key-value pairs continue to exist.
-func (t *Tags) TagString(key, v string) *Tags {
-	return &Tags{key: key, value: v, parent: t}
-}
-
-// TagFloat creates a new Tags struct having the given key-value pair as the
-// final key-value pair. All existing key-value pairs continue to exist.
-func (t *Tags) TagFloat(key string, v float64) *Tags {
-	return &Tags{key: key, value: v, parent: t}
-}