@@ -78,7 +78,10 @@ func New(info logger.Info) (logger.Logger, error) {

 		return nil, err

 	}

-	extra := info.ExtraAttributes(nil)

+	extra, err := info.ExtraAttributes(nil)

+	if err != nil {

+		return nil, err

+	}

 	bufferLimit := defaultBufferLimit

 	if info.Config[bufferLimitKey] != "" {

@@ -169,6 +172,7 @@ func ValidateLogOpt(cfg map[string]string) error {

 	for key := range cfg {

 		switch key {

 		case "env":

+		case "env-regex":

 		case "labels":

 		case "tag":

 		case addressKey:

@@ -17,13 +17,14 @@ import (

 const (

 	name = "gcplogs"

-	projectOptKey = "gcp-project"

-	logLabelsKey  = "labels"

-	logEnvKey     = "env"

-	logCmdKey     = "gcp-log-cmd"

-	logZoneKey    = "gcp-meta-zone"

-	logNameKey    = "gcp-meta-name"

-	logIDKey      = "gcp-meta-id"

+	projectOptKey  = "gcp-project"

+	logLabelsKey   = "labels"

+	logEnvKey      = "env"

+	logEnvRegexKey = "env-regex"

+	logCmdKey      = "gcp-log-cmd"

+	logZoneKey     = "gcp-meta-zone"

+	logNameKey     = "gcp-meta-name"

+	logIDKey       = "gcp-meta-id"

 )

 var (

@@ -133,6 +134,11 @@ func New(info logger.Info) (logger.Logger, error) {

 		return nil, fmt.Errorf("unable to connect or authenticate with Google Cloud Logging: %v", err)

 	}

+	extraAttributes, err := info.ExtraAttributes(nil)

+	if err != nil {

+		return nil, err

+	}

+

 	l := &gcplogs{

 		logger: lg,

 		container: &containerInfo{

@@ -141,7 +147,7 @@ func New(info logger.Info) (logger.Logger, error) {

 			ImageName: info.ContainerImageName,

 			ImageID:   info.ContainerImageID,

 			Created:   info.ContainerCreated,

-			Metadata:  info.ExtraAttributes(nil),

+			Metadata:  extraAttributes,

 		},

 	}

@@ -185,7 +191,7 @@ func New(info logger.Info) (logger.Logger, error) {

 func ValidateLogOpts(cfg map[string]string) error {

 	for k := range cfg {

 		switch k {

-		case projectOptKey, logLabelsKey, logEnvKey, logCmdKey, logZoneKey, logNameKey, logIDKey:

+		case projectOptKey, logLabelsKey, logEnvKey, logEnvRegexKey, logCmdKey, logZoneKey, logNameKey, logIDKey:

 		default:

 			return fmt.Errorf("%q is not a valid option for the gcplogs driver", k)

 		}

@@ -69,12 +69,17 @@ func New(info logger.Info) (logger.Logger, error) {

 		"_created":        info.ContainerCreated,

 	}

-	extraAttrs := info.ExtraAttributes(func(key string) string {

+	extraAttrs, err := info.ExtraAttributes(func(key string) string {

 		if key[0] == '_' {

 			return key

 		}

 		return "_" + key

 	})

+

+	if err != nil {

+		return nil, err

+	}

+

 	for k, v := range extraAttrs {

 		extra[k] = v

 	}

@@ -156,6 +161,7 @@ func ValidateLogOpt(cfg map[string]string) error {

 		case "tag":

 		case "labels":

 		case "env":

+		case "env-regex":

 		case "gelf-compression-level":

 			i, err := strconv.Atoi(val)

 			if err != nil || i < flate.DefaultCompression || i > flate.BestCompression {

@@ -75,7 +75,10 @@ func New(info logger.Info) (logger.Logger, error) {

 		"CONTAINER_NAME":    info.Name(),

 		"CONTAINER_TAG":     tag,

 	}

-	extraAttrs := info.ExtraAttributes(sanitizeKeyMod)

+	extraAttrs, err := info.ExtraAttributes(sanitizeKeyMod)

+	if err != nil {

+		return nil, err

+	}

 	for k, v := range extraAttrs {

 		vars[k] = v

 	}

@@ -89,6 +92,7 @@ func validateLogOpt(cfg map[string]string) error {

 		switch key {

 		case "labels":

 		case "env":

+		case "env-regex":

 		case "tag":

 		default:

 			return fmt.Errorf("unknown log opt '%s' for journald log driver", key)

@@ -67,7 +67,11 @@ func New(info logger.Info) (logger.Logger, error) {

 	}

 	var extra []byte

-	if attrs := info.ExtraAttributes(nil); len(attrs) > 0 {

+	attrs, err := info.ExtraAttributes(nil)

+	if err != nil {

+		return nil, err

+	}

+	if len(attrs) > 0 {

 		var err error

 		extra, err = json.Marshal(attrs)

 		if err != nil {

@@ -121,6 +125,7 @@ func ValidateLogOpt(cfg map[string]string) error {

 		case "max-size":

 		case "labels":

 		case "env":

+		case "env-regex":

 		default:

 			return fmt.Errorf("unknown log opt '%s' for json-file log driver", key)

 		}

@@ -160,13 +160,13 @@ func TestJSONFileLoggerWithLabelsEnv(t *testing.T) {

 	}

 	defer os.RemoveAll(tmp)

 	filename := filepath.Join(tmp, "container.log")

-	config := map[string]string{"labels": "rack,dc", "env": "environ,debug,ssl"}

+	config := map[string]string{"labels": "rack,dc", "env": "environ,debug,ssl", "env-regex": "^dc"}

 	l, err := New(logger.Info{

 		ContainerID:     cid,

 		LogPath:         filename,

 		Config:          config,

 		ContainerLabels: map[string]string{"rack": "101", "dc": "lhr"},

-		ContainerEnv:    []string{"environ=production", "debug=false", "port=10001", "ssl=true"},

+		ContainerEnv:    []string{"environ=production", "debug=false", "port=10001", "ssl=true", "dc_region=west"},

 	})

 	if err != nil {

 		t.Fatal(err)

@@ -189,11 +189,12 @@ func TestJSONFileLoggerWithLabelsEnv(t *testing.T) {

 		t.Fatal(err)

 	}

 	expected := map[string]string{

-		"rack":    "101",

-		"dc":      "lhr",

-		"environ": "production",

-		"debug":   "false",

-		"ssl":     "true",

+		"rack":      "101",

+		"dc":        "lhr",

+		"environ":   "production",

+		"debug":     "false",

+		"ssl":       "true",

+		"dc_region": "west",

 	}

 	if !reflect.DeepEqual(extra, expected) {

 		t.Fatalf("Wrong log attrs: %q, expected %q", extra, expected)

@@ -78,6 +78,7 @@ func ValidateLogOpt(cfg map[string]string) error {

 	for key := range cfg {

 		switch key {

 		case "env":

+		case "env-regex":

 		case "labels":

 		case "tag":

 		case key:

@@ -3,6 +3,7 @@ package logger

 import (

 	"fmt"

 	"os"

+	"regexp"

 	"strings"

 	"time"

 )

@@ -26,7 +27,7 @@ type Info struct {

 // ExtraAttributes returns the user-defined extra attributes (labels,

 // environment variables) in key-value format. This can be used by log drivers

 // that support metadata to add more context to a log.

-func (info *Info) ExtraAttributes(keyMod func(string) string) map[string]string {

+func (info *Info) ExtraAttributes(keyMod func(string) string) (map[string]string, error) {

 	extra := make(map[string]string)

 	labels, ok := info.Config["labels"]

 	if ok && len(labels) > 0 {

@@ -40,14 +41,15 @@ func (info *Info) ExtraAttributes(keyMod func(string) string) map[string]string

 		}

 	}

+	envMapping := make(map[string]string)

+	for _, e := range info.ContainerEnv {

+		if kv := strings.SplitN(e, "=", 2); len(kv) == 2 {

+			envMapping[kv[0]] = kv[1]

+		}

+	}

+

 	env, ok := info.Config["env"]

 	if ok && len(env) > 0 {

-		envMapping := make(map[string]string)

-		for _, e := range info.ContainerEnv {

-			if kv := strings.SplitN(e, "=", 2); len(kv) == 2 {

-				envMapping[kv[0]] = kv[1]

-			}

-		}

 		for _, l := range strings.Split(env, ",") {

 			if v, ok := envMapping[l]; ok {

 				if keyMod != nil {

@@ -58,7 +60,23 @@ func (info *Info) ExtraAttributes(keyMod func(string) string) map[string]string

 		}

 	}

-	return extra

+	envRegex, ok := info.Config["env-regex"]

+	if ok && len(envRegex) > 0 {

+		re, err := regexp.Compile(envRegex)

+		if err != nil {

+			return nil, err

+		}

+		for k, v := range envMapping {

+			if re.MatchString(k) {

+				if keyMod != nil {

+					k = keyMod(k)

+				}

+				extra[k] = v

+			}

+		}

+	}

+

+	return extra, nil

 }

 // Hostname returns the hostname from the underlying OS.

@@ -39,6 +39,7 @@ const (

 	splunkGzipCompressionKey      = "splunk-gzip"

 	splunkGzipCompressionLevelKey = "splunk-gzip-level"

 	envKey                        = "env"

+	envRegexKey                   = "env-regex"

 	labelsKey                     = "labels"

 	tagKey                        = "tag"

 )

@@ -235,7 +236,10 @@ func New(info logger.Info) (logger.Logger, error) {

 		}

 	}

-	attrs := info.ExtraAttributes(nil)

+	attrs, err := info.ExtraAttributes(nil)

+	if err != nil {

+		return nil, err

+	}

 	var (

 		postMessagesFrequency = getAdvancedOptionDuration(envVarPostMessagesFrequency, defaultPostMessagesFrequency)

@@ -538,6 +542,7 @@ func ValidateLogOpt(cfg map[string]string) error {

 		case splunkGzipCompressionKey:

 		case splunkGzipCompressionLevelKey:

 		case envKey:

+		case envRegexKey:

 		case labelsKey:

 		case tagKey:

 		default:

@@ -25,9 +25,10 @@ func TestValidateLogOpt(t *testing.T) {

 		splunkVerifyConnectionKey:     "true",

 		splunkGzipCompressionKey:      "true",

 		splunkGzipCompressionLevelKey: "1",

-		envKey:    "a",

-		labelsKey: "b",

-		tagKey:    "c",

+		envKey:      "a",

+		envRegexKey: "^foo",

+		labelsKey:   "b",

+		tagKey:      "c",

 	})

 	if err != nil {

 		t.Fatal(err)

@@ -215,8 +216,9 @@ func TestInlineFormatWithNonDefaultOptions(t *testing.T) {

 			splunkIndexKey:           "myindex",

 			splunkFormatKey:          splunkFormatInline,

 			splunkGzipCompressionKey: "true",

-			tagKey:    "{{.ImageName}}/{{.Name}}",

-			labelsKey: "a",

+			tagKey:      "{{.ImageName}}/{{.Name}}",

+			labelsKey:   "a",

+			envRegexKey: "^foo",

 		},

 		ContainerID:        "containeriid",

 		ContainerName:      "/container_name",

@@ -225,6 +227,7 @@ func TestInlineFormatWithNonDefaultOptions(t *testing.T) {

 		ContainerLabels: map[string]string{

 			"a": "b",

 		},

+		ContainerEnv: []string{"foo_finder=bar"},

 	}

 	hostname, err := info.Hostname()

@@ -295,6 +298,7 @@ func TestInlineFormatWithNonDefaultOptions(t *testing.T) {

 			event["source"] != "stdout" ||

 			event["tag"] != "container_image_name/container_name" ||

 			event["attrs"].(map[string]interface{})["a"] != "b" ||

+			event["attrs"].(map[string]interface{})["foo_finder"] != "bar" ||

 			len(event) != 4 {

 			t.Fatalf("Unexpected event in message %v", event)

 		}

@@ -184,6 +184,7 @@ func ValidateLogOpt(cfg map[string]string) error {

 	for key := range cfg {

 		switch key {

 		case "env":

+		case "env-regex":

 		case "labels":

 		case "syslog-address":

 		case "syslog-facility":