diff --git a/log/api.go b/log/api.go
index f8d5213..dc2a48d 100644
--- a/log/api.go
+++ b/log/api.go
@@ -31,8 +31,7 @@ func Errorf(ctx context.Context, err error, format string, args ...interface{})
 
 // From returns a copied logger from the context that you can use to access logger API.
 func From(ctx context.Context) Logger {
-	f := getFields(ctx)
-	return f.configureLogger(ctx, f.getCopiedLogger().(fieldSetter))
+	return from(ctx, getFields(ctx))
 }
 
 // Info logs from context at the debug level.
@@ -45,6 +44,21 @@ func Infof(ctx context.Context, format string, args ...interface{}) {
 	Fields{}.Infof(ctx, format, args...)
 }
 
+// RegisterListener registers callbacks that are called after a log.
+func RegisterListener(ctx context.Context, callback func(context.Context, Fields)) context.Context{
+	cbList, isList := ctx.Value(listenerKey{}).([]func(context.Context, Fields))
+	if !isList {
+		cbList = []func(context.Context, Fields){callback}
+	} else {
+		cbList = append(cbList, callback)
+	}
+	return context.WithValue(
+		context.WithValue(ctx, canonicalFieldsKey{}, frozen.NewMapBuilder(0)),
+		listenerKey{},
+		cbList,
+	)
+}
+
 // Suppress will ensure that suppressed keys are not logged.
 func Suppress(keys ...string) Fields {
 	return Fields{}.Suppress(keys...)
@@ -162,9 +176,8 @@ func (f Fields) WithLogger(logger Logger) Fields {
 
 // String returns a string that represent the current fields
 func (f Fields) String(ctx context.Context) string {
-	fields := &fieldsCollector{}
-	f.configureLogger(ctx, fields)
-	return fields.fields.String()
+	m, _ := f.getResolvedFields(ctx)
+	return m.String()
 }
 
 // MergedString returns a string that represents the current fields merged by fields in context
diff --git a/log/canonical.go b/log/canonical.go
new file mode 100644
index 0000000..c1808b3
--- /dev/null
+++ b/log/canonical.go
@@ -0,0 +1,26 @@
+package log
+
+import (
+	"context"
+
+	"github.com/arr-ai/frozen"
+)
+
+// OnLog is a callback that is called when fields and configurations are added to the logger.
+func OnLog(ctx context.Context, fields Fields) {
+	if fields := ctx.Value(canonicalFieldsKey{}); fields == nil {
+		Info(ctx, "Canonical fields have not been set up properly, fields will not be collected")
+		return
+	}
+	addCanonicalFields(getCanonicalFields(ctx), fields)
+}
+
+// CanonicalLog logs all the collected fields from previous logs in non-verbose mode.
+func CanonicalLog(ctx context.Context) {
+	from(ctx, Fields{getCanonicalFields(ctx).Finish()}).Info()
+}
+
+// WithCanonicalLog creates a canonical fields collector.
+func WithCanonicalLog(ctx context.Context) context.Context {
+	return context.WithValue(ctx, canonicalFieldsKey{}, frozen.NewMapBuilder(0))
+}
diff --git a/log/canonical_test.go b/log/canonical_test.go
new file mode 100644
index 0000000..94799f7
--- /dev/null
+++ b/log/canonical_test.go
@@ -0,0 +1,62 @@
+package log
+
+import (
+	"context"
+	"testing"
+
+	"github.com/alecthomas/assert"
+	"github.com/arr-ai/frozen"
+)
+
+func TestCanonicalLog(t *testing.T) {
+	t.Parallel()
+
+	ctx := WithCanonicalLog(context.Background())
+	logger := newMockLogger()
+
+	mb := getCanonicalFields(ctx)
+
+	addValues(mb, logger)
+	setLogMockAssertion(logger, mb.Finish().Without(frozen.NewSet(loggerKey{})))
+	logger.On("Info")
+
+	// add the same values again because Finish would remove the values from the map builder.
+	addValues(mb, logger)
+	CanonicalLog(ctx)
+
+	logger.AssertExpectations(t)
+}
+
+func TestOnLogWithoutCanonicalFieldsSetup(t *testing.T) {
+	t.Parallel()
+
+	logger := newMockLogger()
+	logger.On("Info", "Canonical fields have not been set up properly, fields will not be collected")
+	setLogMockAssertion(logger, frozen.NewMap())
+	OnLog(WithLogger(logger).Onto(context.Background()), Fields{frozen.NewMap()})
+	logger.AssertExpectations(t)
+}
+
+func TestOnLog(t *testing.T) {
+	t.Parallel()
+
+	ctx := WithCanonicalLog(context.Background())
+	mb := getCanonicalFields(ctx)
+	addValues(mb, newMockLogger())
+
+	testField := frozen.NewMap().With("additional", "value").With("1", 1).With("byte", 'l')
+	OnLog(ctx, Fields{testField})
+
+	m := mb.Finish()
+	for i := testField.Range(); i.Next(); {
+		val, exists := m.Get(i.Key())
+		assert.True(t, exists && val == i.Value())
+	}
+}
+
+func addValues(mb *frozen.MapBuilder, logger Logger) {
+	mb.Put("test", 1)
+	mb.Put("test2", 'k')
+	mb.Put("test3", "string value")
+	mb.Put(loggerKey{}, logger)
+}
\ No newline at end of file
diff --git a/log/util.go b/log/util.go
index a2cac97..303da26 100644
--- a/log/util.go
+++ b/log/util.go
@@ -9,6 +9,8 @@ import (
 const errMsgKey = "error_message"
 
 type fieldsContextKey struct{}
+type canonicalFieldsKey struct{}
+type listenerKey struct {}
 type loggerKey struct{}
 type suppress struct{}
 type ctxRef struct{ ctxKey interface{} }
@@ -30,10 +32,26 @@ func (f Fields) getCopiedLogger() Logger {
 	return logger.(copyable).Copy()
 }
 
-func (f Fields) configureLogger(ctx context.Context, logger fieldSetter) Logger {
+func configureLogger(logger fieldSetter, fields frozen.Map, configs []Config) Logger {
+	return applyConfiguration(logger.(Logger), configs).(fieldSetter).PutFields(fields)
+}
+
+func applyConfiguration(logger Logger, configs []Config) Logger {
+	for _, c := range configs {
+		err := c.Apply(logger.(Logger))
+		if err != nil {
+			//TODO: should decide whether it should panic or not
+			panic(err)
+		}
+	}
+	return logger
+}
+
+func (f Fields) getResolvedFields(ctx context.Context) (frozen.Map, []Config) {
 	fields := f.m
 	var toSuppress frozen.SetBuilder
 	toSuppress.Add(loggerKey{})
+	configs := make([]Config, 0)
 	for i := fields.Range(); i.Next(); {
 		switch k := i.Value().(type) {
 		case ctxRef:
@@ -52,20 +70,58 @@ func (f Fields) configureLogger(ctx context.Context, logger fieldSetter) Logger
 			toSuppress.Add(i.Key())
 		case Config:
 			toSuppress.Add(i.Key())
-			err := k.Apply(logger.(Logger))
-			if err != nil {
-				//TODO: should decide whether it should panic or not
-				panic(err)
-			}
+			configs = append(configs, k)
 		}
 	}
-	return logger.PutFields(fields.Without(toSuppress.Finish()))
+	return fields.Without(toSuppress.Finish()), configs
 }
 
 func (f Fields) with(key, val interface{}) Fields {
 	return Fields{f.m.With(key, val)}
 }
 
+func getCanonicalFields(ctx context.Context) *frozen.MapBuilder {
+	mb, exists := ctx.Value(canonicalFieldsKey{}).(*frozen.MapBuilder)
+	if !exists {
+		return frozen.NewMapBuilder(0)
+	}
+	return mb
+}
+
+func addCanonicalFields(mb *frozen.MapBuilder, fields Fields) {
+	for i := fields.m.Range(); i.Next(); {
+		switch k := i.Key().(type) {
+		case Config, Logger:
+			mb.Put(k, i.Value())
+		default:
+			if f, exists := mb.Get(k); exists {
+				if	val, isList := f.([]interface{}); isList {
+					mb.Put(k, append(val, i.Value()))
+				} else {
+					mb.Put(k, []interface{}{f, i.Value()})
+				}
+			} else {
+				mb.Put(k, i.Value())
+			}
+		}
+	}
+}
+
+func doCallbacks(ctx context.Context, fields Fields) {
+	callbacks := ctx.Value(listenerKey{})
+	if callbacks != nil {
+		for _, c := range callbacks.([]func(context.Context, Fields)) {
+			c(ctx, fields)
+		}
+	}
+}
+
+func from(ctx context.Context, f Fields) Logger {
+	fields, configs := f.getResolvedFields(ctx)
+	doCallbacks(ctx, Fields{fields})
+	return configureLogger(f.getCopiedLogger().(fieldSetter), fields, configs)
+}
+
 func getFields(ctx context.Context) Fields {
 	fields, exists := ctx.Value(fieldsContextKey{}).(frozen.Map)
 	if !exists {
diff --git a/log/util_test.go b/log/util_test.go
index 24b3798..550bd24 100644
--- a/log/util_test.go
+++ b/log/util_test.go
@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/arr-ai/frozen"
+	"github.com/stretchr/testify/assert"
 )
 
 type key1 struct{}
@@ -75,7 +76,7 @@ func TestConfigureLogger(t *testing.T) {
 			for i := c.contextFields.Range(); i.Next(); {
 				ctx = context.WithValue(ctx, i.Key(), i.Value())
 			}
-			Fields{c.unresolveds}.configureLogger(ctx, Logger(logger).(fieldSetter))
+			logger = configureLogger(Logger(logger).(fieldSetter), c.expected, []Config{}).(*mockLogger)
 			logger.AssertExpectations(t)
 		})
 	}
@@ -86,7 +87,7 @@ func TestConfigureLoggerWithConfigs(t *testing.T) {
 
 	//TODO: add more configs
 	testCase := getUnresolvedFieldsCases()[0]
-	unresolveds := Fields{testCase.unresolveds}.WithConfigs(NewJSONFormat())
+	unresolved := Fields{testCase.unresolveds}.WithConfigs(NewJSONFormat())
 	expected := testCase.expected
 
 	logger := newMockLogger()
@@ -97,7 +98,24 @@ func TestConfigureLoggerWithConfigs(t *testing.T) {
 	for i := testCase.contextFields.Range(); i.Next(); {
 		ctx = context.WithValue(ctx, i.Key(), i.Value())
 	}
-
-	unresolveds.configureLogger(ctx, Logger(logger).(fieldSetter))
+	resolved, configs := unresolved.getResolvedFields(ctx)
+	configureLogger(Logger(logger).(fieldSetter), resolved, configs)
 	logger.AssertExpectations(t)
 }
+
+func TestRegisterListener(t *testing.T) {
+	t.Parallel()
+
+	mockListener1 := OnLog
+
+	ctx := RegisterListener(context.Background(), mockListener1)
+	cbs, isCallbackList := ctx.Value(listenerKey{}).([]func(context.Context, Fields))
+	assert.True(t, isCallbackList)
+	assert.Equal(t, 1, len(cbs))
+
+	mockListener2 := func(context.Context, Fields){}
+	ctx = RegisterListener(ctx, mockListener2)
+	cbs, isCallbackList = ctx.Value(listenerKey{}).([]func(context.Context, Fields))
+	assert.True(t, isCallbackList)
+	assert.Equal(t, 2, len(cbs))
+}