Gzip: support for min_length.

caddy/setup/gzip.go

@@ -27,9 +27,13 @@ func gzipParse(c *Controller) ([]gzip.Config, error) {
 	for c.Next() {
 		config := gzip.Config{}
 
+		// Request Filters
 		pathFilter := gzip.PathFilter{IgnoredPaths: make(gzip.Set)}
 		extFilter := gzip.ExtFilter{Exts: make(gzip.Set)}
 
+		// Response Filters
+		lengthFilter := gzip.LengthFilter(0)
+
 		// No extra args expected
 		if len(c.RemainingArgs()) > 0 {
 			return configs, c.ArgErr()
@@ -68,24 +72,42 @@ func gzipParse(c *Controller) ([]gzip.Config, error) {
 				}
 				level, _ := strconv.Atoi(c.Val())
 				config.Level = level
+			case "min_length":
+				if !c.NextArg() {
+					return configs, c.ArgErr()
+				}
+				length, err := strconv.ParseInt(c.Val(), 10, 64)
+				if err != nil {
+					return configs, err
+				} else if length == 0 {
+					return configs, fmt.Errorf(`gzip: min_length must be greater than 0`)
+				}
+				lengthFilter = gzip.LengthFilter(length)
 			default:
 				return configs, c.ArgErr()
 			}
 		}
 
-		config.Filters = []gzip.Filter{}
+		// Request Filters
+		config.RequestFilters = []gzip.RequestFilter{}
 
 		// If ignored paths are specified, put in front to filter with path first
 		if len(pathFilter.IgnoredPaths) > 0 {
-			config.Filters = []gzip.Filter{pathFilter}
+			config.RequestFilters = []gzip.RequestFilter{pathFilter}
 		}
 
 		// Then, if extensions are specified, use those to filter.
 		// Otherwise, use default extensions filter.
 		if len(extFilter.Exts) > 0 {
-			config.Filters = append(config.Filters, extFilter)
+			config.RequestFilters = append(config.RequestFilters, extFilter)
 		} else {
-			config.Filters = append(config.Filters, gzip.DefaultExtFilter())
+			config.RequestFilters = append(config.RequestFilters, gzip.DefaultExtFilter())
+		}
+
+		// Response Filters
+		// If min_length is specified, use it.
+		if int64(lengthFilter) != 0 {
+			config.ResponseFilters = append(config.ResponseFilters, lengthFilter)
 		}
 
 		configs = append(configs, config)

caddy/setup/gzip_test.go

@@ -73,6 +73,18 @@ func TestGzip(t *testing.T) {
 		 level 1
 		}
 		`, false},
+		{`gzip { not /file
+		 ext *
+		 level 1
+		 min_length ab
+		}
+		`, true},
+		{`gzip { not /file
+		 ext *
+		 level 1
+		 min_length 1000
+		}
+		`, false},
 	}
 	for i, test := range tests {
 		c := NewTestController(test.input)

middleware/gzip/gzip.go

@@ -23,8 +23,9 @@ type Gzip struct {
 
 // Config holds the configuration for Gzip middleware
 type Config struct {
-	Filters []Filter // Filters to use
-	Level   int      // Compression level
+	RequestFilters  []RequestFilter
+	ResponseFilters []ResponseFilter
+	Level           int // Compression level
 }
 
 // ServeHTTP serves a gzipped response if the client supports it.
@@ -36,8 +37,8 @@ func (g Gzip) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
 outer:
 	for _, c := range g.Configs {
 
-		// Check filters to determine if gzipping is permitted for this request
-		for _, filter := range c.Filters {
+		// Check request filters to determine if gzipping is permitted for this request
+		for _, filter := range c.RequestFilters {
 			if !filter.ShouldCompress(r) {
 				continue outer
 			}
@@ -56,8 +57,17 @@ outer:
 		defer gzipWriter.Close()
 		gz := gzipResponseWriter{Writer: gzipWriter, ResponseWriter: w}
 
+		var rw http.ResponseWriter
+		// if no response filter is used
+		if len(c.ResponseFilters) == 0 {
+			rw = gz
+		} else {
+			// wrap gzip writer with ResponseFilterWriter
+			rw = NewResponseFilterWriter(c.ResponseFilters, gz)
+		}
+
 		// Any response in forward middleware will now be compressed
-		status, err := g.Next.ServeHTTP(gz, r)
+		status, err := g.Next.ServeHTTP(rw, r)
 
 		// If there was an error that remained unhandled, we need
 		// to send something back before gzipWriter gets closed at

middleware/gzip/gzip_test.go

@@ -21,7 +21,7 @@ func TestGzipHandler(t *testing.T) {
 		extFilter.Exts.Add(e)
 	}
 	gz := Gzip{Configs: []Config{
-		{Filters: []Filter{pathFilter, extFilter}},
+		{RequestFilters: []RequestFilter{pathFilter, extFilter}},
 	}}
 
 	w := httptest.NewRecorder()

middleware/gzip/request_filter.go

@@ -7,8 +7,8 @@ import (
 	"github.com/mholt/caddy/middleware"
 )
 
-// Filter determines if a request should be gzipped.
-type Filter interface {
+// RequestFilter determines if a request should be gzipped.
+type RequestFilter interface {
 	// ShouldCompress tells if gzip compression
 	// should be done on the request.
 	ShouldCompress(*http.Request) bool
@@ -26,7 +26,7 @@ func DefaultExtFilter() ExtFilter {
 	return m
 }
 
-// ExtFilter is Filter for file name extensions.
+// ExtFilter is RequestFilter for file name extensions.
 type ExtFilter struct {
 	// Exts is the file name extensions to accept
 	Exts Set
@@ -43,7 +43,7 @@ func (e ExtFilter) ShouldCompress(r *http.Request) bool {
 	return e.Exts.Contains(ExtWildCard) || e.Exts.Contains(ext)
 }
 
-// PathFilter is Filter for request path.
+// PathFilter is RequestFilter for request path.
 type PathFilter struct {
 	// IgnoredPaths is the paths to ignore
 	IgnoredPaths Set

middleware/gzip/request_filter_test.go

@@ -47,7 +47,7 @@ func TestSet(t *testing.T) {
 }
 
 func TestExtFilter(t *testing.T) {
-	var filter Filter = ExtFilter{make(Set)}
+	var filter RequestFilter = ExtFilter{make(Set)}
 	for _, e := range []string{".txt", ".html", ".css", ".md"} {
 		filter.(ExtFilter).Exts.Add(e)
 	}
@@ -86,7 +86,7 @@ func TestPathFilter(t *testing.T) {
 	paths := []string{
 		"/a", "/b", "/c", "/de",
 	}
-	var filter Filter = PathFilter{make(Set)}
+	var filter RequestFilter = PathFilter{make(Set)}
 	for _, p := range paths {
 		filter.(PathFilter).IgnoredPaths.Add(p)
 	}

middleware/gzip/response_filter.go

@@ -0,0 +1,62 @@
+package gzip
+
+import (
+	"net/http"
+	"strconv"
+)
+
+// ResponseFilter determines if the response should be gzipped.
+type ResponseFilter interface {
+	ShouldCompress(http.ResponseWriter) bool
+}
+
+// LengthFilter is ResponseFilter for minimum content length.
+type LengthFilter int64
+
+// ShouldCompress returns if content length is greater than or
+// equals to minimum length.
+func (l LengthFilter) ShouldCompress(w http.ResponseWriter) bool {
+	contentLength := (w.Header().Get("Content-Length"))
+	length, err := strconv.ParseInt(contentLength, 10, 64)
+	if err != nil || length == 0 {
+		return false
+	}
+	return l != 0 && int64(l) <= length
+}
+
+// ResponseFilterWriter validates ResponseFilters. It writes
+// gzip compressed data if ResponseFilters are satisfied or
+// uncompressed data otherwise.
+type ResponseFilterWriter struct {
+	filters        []ResponseFilter
+	validated      bool
+	shouldCompress bool
+	gzipResponseWriter
+}
+
+// NewResponseFilterWriter creates and initializes a new ResponseFilterWriter.
+func NewResponseFilterWriter(filters []ResponseFilter, gz gzipResponseWriter) *ResponseFilterWriter {
+	return &ResponseFilterWriter{filters: filters, gzipResponseWriter: gz}
+}
+
+// Write wraps underlying Write method and compresses if filters
+// are satisfied
+func (r *ResponseFilterWriter) Write(b []byte) (int, error) {
+	// One time validation to determine if compression should
+	// be used or not.
+	if !r.validated {
+		r.shouldCompress = true
+		for _, filter := range r.filters {
+			if !filter.ShouldCompress(r) {
+				r.shouldCompress = false
+				break
+			}
+		}
+		r.validated = true
+	}
+
+	if r.shouldCompress {
+		return r.gzipResponseWriter.Write(b)
+	}
+	return r.ResponseWriter.Write(b)
+}

middleware/gzip/response_filter_test.go

@@ -0,0 +1,70 @@
+package gzip
+
+import (
+	"compress/gzip"
+	"fmt"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestLengthFilter(t *testing.T) {
+	var filters []ResponseFilter = []ResponseFilter{
+		LengthFilter(100),
+		LengthFilter(1000),
+		LengthFilter(0),
+	}
+
+	var tests = []struct {
+		length         int64
+		shouldCompress [3]bool
+	}{
+		{20, [3]bool{false, false, false}},
+		{50, [3]bool{false, false, false}},
+		{100, [3]bool{true, false, false}},
+		{500, [3]bool{true, false, false}},
+		{1000, [3]bool{true, true, false}},
+		{1500, [3]bool{true, true, false}},
+	}
+
+	for i, ts := range tests {
+		for j, filter := range filters {
+			r := httptest.NewRecorder()
+			r.Header().Set("Content-Length", fmt.Sprint(ts.length))
+			if filter.ShouldCompress(r) != ts.shouldCompress[j] {
+				t.Errorf("Test %v: Expected %v found %v", i, ts.shouldCompress[j], filter.ShouldCompress(r))
+			}
+		}
+	}
+}
+
+func TestResponseFilterWriter(t *testing.T) {
+	tests := []struct {
+		body           string
+		shouldCompress bool
+	}{
+		{"Hello\t\t\t\n", false},
+		{"Hello the \t\t\t world is\n\n\n great", true},
+		{"Hello \t\t\nfrom gzip", true},
+		{"Hello gzip\n", false},
+	}
+	filters := []ResponseFilter{
+		LengthFilter(15),
+	}
+	for i, ts := range tests {
+		w := httptest.NewRecorder()
+		w.Header().Set("Content-Length", fmt.Sprint(len(ts.body)))
+		gz := gzipResponseWriter{gzip.NewWriter(w), w}
+		rw := NewResponseFilterWriter(filters, gz)
+		rw.Write([]byte(ts.body))
+		resp := w.Body.String()
+		if !ts.shouldCompress {
+			if resp != ts.body {
+				t.Errorf("Test %v: No compression expected, found %v", i, resp)
+			}
+		} else {
+			if resp == ts.body {
+				t.Errorf("Test %v: Compression expected, found %v", i, resp)
+			}
+		}
+	}
+}