logging: Automatic wrap default for filter encoder (#5980)

Co-authored-by: Kévin Dunglas <kevin@dunglas.fr>

caddytest/integration/caddyfile_adapt/log_filter_no_wrap.txt

@@ -0,0 +1,52 @@
+:80
+
+log {
+	output stdout
+	format filter {
+		fields {
+			request>headers>Server delete
+		}
+	}
+}
+----------
+{
+	"logging": {
+		"logs": {
+			"default": {
+				"exclude": [
+					"http.log.access.log0"
+				]
+			},
+			"log0": {
+				"writer": {
+					"output": "stdout"
+				},
+				"encoder": {
+					"fields": {
+						"request\u003eheaders\u003eServer": {
+							"filter": "delete"
+						}
+					},
+					"format": "filter"
+				},
+				"include": [
+					"http.log.access.log0"
+				]
+			}
+		}
+	},
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":80"
+					],
+					"logs": {
+						"default_logger_name": "log0"
+					}
+				}
+			}
+		}
+	}
+}

logging.go

@@ -265,6 +265,17 @@ type WriterOpener interface {
 	OpenWriter() (io.WriteCloser, error)
 }
 
+// IsWriterStandardStream returns true if the input is a
+// writer-opener to a standard stream (stdout, stderr).
+func IsWriterStandardStream(wo WriterOpener) bool {
+	switch wo.(type) {
+	case StdoutWriter, StderrWriter,
+		*StdoutWriter, *StderrWriter:
+		return true
+	}
+	return false
+}
+
 type writerDestructor struct {
 	io.WriteCloser
 }
@@ -341,16 +352,18 @@ func (cl *BaseLog) provisionCommon(ctx Context, logging *Logging) error {
 			return fmt.Errorf("loading log encoder module: %v", err)
 		}
 		cl.encoder = mod.(zapcore.Encoder)
+
+		// if the encoder module needs the writer to determine
+		// the correct default to use for a nested encoder, we
+		// pass it down as a secondary provisioning step
+		if cfd, ok := mod.(ConfiguresFormatterDefault); ok {
+			if err := cfd.ConfigureDefaultFormat(cl.writerOpener); err != nil {
+				return fmt.Errorf("configuring default format for encoder module: %v", err)
+			}
+		}
 	}
 	if cl.encoder == nil {
-		// only allow colorized output if this log is going to stdout or stderr
-		var colorize bool
-		switch cl.writerOpener.(type) {
-		case StdoutWriter, StderrWriter,
-			*StdoutWriter, *StderrWriter:
-			colorize = true
-		}
-		cl.encoder = newDefaultProductionLogEncoder(colorize)
+		cl.encoder = newDefaultProductionLogEncoder(cl.writerOpener)
 	}
 	cl.buildCore()
 	return nil
@@ -680,7 +693,7 @@ func newDefaultProductionLog() (*defaultCustomLog, error) {
 	if err != nil {
 		return nil, err
 	}
-	cl.encoder = newDefaultProductionLogEncoder(true)
+	cl.encoder = newDefaultProductionLogEncoder(cl.writerOpener)
 	cl.levelEnabler = zapcore.InfoLevel
 
 	cl.buildCore()
@@ -697,16 +710,14 @@ func newDefaultProductionLog() (*defaultCustomLog, error) {
 	}, nil
 }
 
-func newDefaultProductionLogEncoder(colorize bool) zapcore.Encoder {
+func newDefaultProductionLogEncoder(wo WriterOpener) zapcore.Encoder {
 	encCfg := zap.NewProductionEncoderConfig()
-	if term.IsTerminal(int(os.Stdout.Fd())) {
+	if IsWriterStandardStream(wo) && term.IsTerminal(int(os.Stderr.Fd())) {
 		// if interactive terminal, make output more human-readable by default
 		encCfg.EncodeTime = func(ts time.Time, encoder zapcore.PrimitiveArrayEncoder) {
 			encoder.AppendString(ts.UTC().Format("2006/01/02 15:04:05.000"))
 		}
-		if colorize {
-			encCfg.EncodeLevel = zapcore.CapitalColorLevelEncoder
-		}
+		encCfg.EncodeLevel = zapcore.CapitalColorLevelEncoder
 		return zapcore.NewConsoleEncoder(encCfg)
 	}
 	return zapcore.NewJSONEncoder(encCfg)
@@ -753,6 +764,15 @@ var (
 
 var writers = NewUsagePool()
 
+// ConfiguresFormatterDefault is an optional interface that
+// encoder modules can implement to configure the default
+// format of their encoder. This is useful for encoders
+// which nest an encoder, that needs to know the writer
+// in order to determine the correct default.
+type ConfiguresFormatterDefault interface {
+	ConfigureDefaultFormat(WriterOpener) error
+}
+
 const DefaultLoggerName = "default"
 
 // Interface guards

modules/logging/filterencoder.go

@@ -17,11 +17,13 @@ package logging
 import (
 	"encoding/json"
 	"fmt"
+	"os"
 	"time"
 
 	"go.uber.org/zap"
 	"go.uber.org/zap/buffer"
 	"go.uber.org/zap/zapcore"
+	"golang.org/x/term"
 
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig"
@@ -36,8 +38,10 @@ func init() {
 // log entries before they are actually encoded by
 // an underlying encoder.
 type FilterEncoder struct {
-	// The underlying encoder that actually
-	// encodes the log entries. Required.
+	// The underlying encoder that actually encodes the
+	// log entries. If not specified, defaults to "json",
+	// unless the output is a terminal, in which case
+	// it defaults to "console".
 	WrappedRaw json.RawMessage `json:"wrap,omitempty" caddy:"namespace=caddy.logging.encoders inline_key=format"`
 
 	// A map of field names to their filters. Note that this
@@ -59,6 +63,9 @@ type FilterEncoder struct {
 
 	// used to keep keys unique across nested objects
 	keyPrefix string
+
+	wrappedIsDefault bool
+	ctx              caddy.Context
 }
 
 // CaddyModule returns the Caddy module information.
@@ -71,16 +78,25 @@ func (FilterEncoder) CaddyModule() caddy.ModuleInfo {
 
 // Provision sets up the encoder.
 func (fe *FilterEncoder) Provision(ctx caddy.Context) error {
-	if fe.WrappedRaw == nil {
-		return fmt.Errorf("missing \"wrap\" (must specify an underlying encoder)")
-	}
+	fe.ctx = ctx
 
-	// set up wrapped encoder (required)
-	val, err := ctx.LoadModule(fe, "WrappedRaw")
-	if err != nil {
-		return fmt.Errorf("loading fallback encoder module: %v", err)
+	if fe.WrappedRaw == nil {
+		// if wrap is not specified, default to JSON
+		fe.wrapped = &JSONEncoder{}
+		if p, ok := fe.wrapped.(caddy.Provisioner); ok {
+			if err := p.Provision(ctx); err != nil {
+				return fmt.Errorf("provisioning fallback encoder module: %v", err)
+			}
+		}
+		fe.wrappedIsDefault = true
+	} else {
+		// set up wrapped encoder
+		val, err := ctx.LoadModule(fe, "WrappedRaw")
+		if err != nil {
+			return fmt.Errorf("loading fallback encoder module: %v", err)
+		}
+		fe.wrapped = val.(zapcore.Encoder)
 	}
-	fe.wrapped = val.(zapcore.Encoder)
 
 	// set up each field filter
 	if fe.Fields == nil {
@@ -97,6 +113,29 @@ func (fe *FilterEncoder) Provision(ctx caddy.Context) error {
 	return nil
 }
 
+// ConfigureDefaultFormat will set the default format to "console"
+// if the writer is a terminal. If already configured as a filter
+// encoder, it passes through the writer so a deeply nested filter
+// encoder can configure its own default format.
+func (fe *FilterEncoder) ConfigureDefaultFormat(wo caddy.WriterOpener) error {
+	if !fe.wrappedIsDefault {
+		if cfd, ok := fe.wrapped.(caddy.ConfiguresFormatterDefault); ok {
+			return cfd.ConfigureDefaultFormat(wo)
+		}
+		return nil
+	}
+
+	if caddy.IsWriterStandardStream(wo) && term.IsTerminal(int(os.Stderr.Fd())) {
+		fe.wrapped = &ConsoleEncoder{}
+		if p, ok := fe.wrapped.(caddy.Provisioner); ok {
+			if err := p.Provision(fe.ctx); err != nil {
+				return fmt.Errorf("provisioning fallback encoder module: %v", err)
+			}
+		}
+	}
+	return nil
+}
+
 // UnmarshalCaddyfile sets up the module from Caddyfile tokens. Syntax:
 //
 //	filter {
@@ -390,7 +429,8 @@ func (mom logObjectMarshalerWrapper) MarshalLogObject(_ zapcore.ObjectEncoder) e
 
 // Interface guards
 var (
-	_ zapcore.Encoder         = (*FilterEncoder)(nil)
-	_ zapcore.ObjectMarshaler = (*logObjectMarshalerWrapper)(nil)
-	_ caddyfile.Unmarshaler   = (*FilterEncoder)(nil)
+	_ zapcore.Encoder                  = (*FilterEncoder)(nil)
+	_ zapcore.ObjectMarshaler          = (*logObjectMarshalerWrapper)(nil)
+	_ caddyfile.Unmarshaler            = (*FilterEncoder)(nil)
+	_ caddy.ConfiguresFormatterDefault = (*FilterEncoder)(nil)
 )