add support of custom 404 page for assets server

README.md

@@ -196,6 +196,8 @@ There are two ways to set cache duration:
 1. A single value for all static assets. This is as simple as `--assets.cache=48h`.
 2. Custom duration for different mime types. It should include two parts - the default value and the pairs of mime:duration. In command line this looks like multiple `--assets.cache` options, i.e. `--assets.cache=48h --assets.cache=text/html:24h --assets.cache=image/png:2h`. Environment values should be comma-separated, i.e. `ASSETS_CACHE=48h,text/html:24h,image/png:2h`
 
+Custom 404 (not found) page can be set with `--assets.404=<path>` parameter. The path should be relative to the assets root.
+
 ## Using reproxy as a base image
 
 Serving purely static content is one of the popular use cases. Usually this used for the separate frontend container providing UI only. With the assets server such a container is almost trivial to make. This is an example from the container serving [reproxy.io](http://reproxy.io)
@@ -365,6 +367,7 @@ assets:
       --assets.root=                assets web root (default: /) [$ASSETS_ROOT]
       --assets.spa                  spa treatment for assets [$ASSETS_SPA]
       --assets.cache=               cache duration for assets [$ASSETS_CACHE]
+      --assets.not-found=           path to file to serve on 404, relative to location [$ASSETS_NOT_FOUND]
 
 logger:
       --logger.stdout               enable stdout logging [$LOGGER_STDOUT]

app/main.go

@@ -36,10 +36,10 @@ var opts struct {
 	DropHeaders       []string `long:"drop-header" env:"DROP_HEADERS" description:"incoming headers to drop" env-delim:","`
 	AuthBasicHtpasswd string   `long:"basic-htpasswd" env:"BASIC_HTPASSWD" description:"htpasswd file for basic auth"`
 
-	LBType string `long:"lb-type" env:"LB_TYPE" description:"load balancer type" choice:"random" choice:"failover" default:"random"` //nolint
+	LBType string `long:"lb-type" env:"LB_TYPE" description:"load balancer type" choice:"random" choice:"failover" default:"random"` // nolint
 
 	SSL struct {
-		Type          string   `long:"type" env:"TYPE" description:"ssl (auto) support" choice:"none" choice:"static" choice:"auto" default:"none"` //nolint
+		Type          string   `long:"type" env:"TYPE" description:"ssl (auto) support" choice:"none" choice:"static" choice:"auto" default:"none"` // nolint
 		Cert          string   `long:"cert" env:"CERT" description:"path to cert.pem file"`
 		Key           string   `long:"key" env:"KEY" description:"path to key.pem file"`
 		ACMELocation  string   `long:"acme-location" env:"ACME_LOCATION" description:"dir where certificates will be stored by autocert manager" default:"./var/acme"`
@@ -53,6 +53,7 @@ var opts struct {
 		WebRoot      string   `long:"root" env:"ROOT" default:"/" description:"assets web root"`
 		SPA          bool     `long:"spa" env:"SPA" description:"spa treatment for assets"`
 		CacheControl []string `long:"cache" env:"CACHE" description:"cache duration for assets" env-delim:","`
+		NotFound     string   `long:"not-found" env:"NOT_FOUND" description:"path to file to serve on 404, relative to location"`
 	} `group:"assets" namespace:"assets" env-namespace:"ASSETS"`
 
 	Logger struct {
@@ -240,6 +241,7 @@ func run() error {
 		MaxBodySize:    int64(maxBodySize),
 		AssetsLocation: opts.Assets.Location,
 		AssetsWebRoot:  opts.Assets.WebRoot,
+		Assets404:      opts.Assets.NotFound,
 		AssetsSPA:      opts.Assets.SPA,
 		CacheControl:   cacheControl,
 		GzEnabled:      opts.GzipEnabled,

app/proxy/proxy.go

@@ -1,6 +1,7 @@
 package proxy
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"io"
@@ -9,6 +10,8 @@ import (
 	"net/http"
 	"net/http/httputil"
 	"net/url"
+	"os"
+	"path/filepath"
 	"regexp"
 	"strconv"
 	"strings"
@@ -28,6 +31,7 @@ type Http struct { // nolint golint
 	Address         string
 	AssetsLocation  string
 	AssetsWebRoot   string
+	Assets404       string
 	AssetsSPA       bool
 	MaxBodySize     int64
 	GzEnabled       bool
@@ -91,6 +95,9 @@ func (h *Http) Run(ctx context.Context) error {
 
 	if h.AssetsLocation != "" {
 		log.Printf("[DEBUG] assets file server enabled for %s, webroot %s", h.AssetsLocation, h.AssetsWebRoot)
+		if h.Assets404 != "" {
+			log.Printf("[DEBUG] assets 404 file enabled for %s", h.Assets404)
+		}
 	}
 
 	if h.LBSelector == nil {
@@ -260,7 +267,7 @@ func (h *Http) proxyHandler() http.HandlerFunc {
 				h.Reporter.Report(w, http.StatusInternalServerError)
 				return
 			}
-			fs, err := h.fileServer(ae[0], ae[1], ae[2] == "spa")
+			fs, err := h.fileServer(ae[0], ae[1], ae[2] == "spa", nil)
 			if err != nil {
 				log.Printf("[WARN] file server error, %v", err)
 				h.Reporter.Report(w, http.StatusInternalServerError)
@@ -327,8 +334,20 @@ func (h *Http) assetsHandler() http.HandlerFunc {
 	if h.AssetsLocation == "" || h.AssetsWebRoot == "" {
 		return func(writer http.ResponseWriter, request *http.Request) {}
 	}
-	log.Printf("[DEBUG] shared assets server enabled for %s %s, spa=%v", h.AssetsWebRoot, h.AssetsLocation, h.AssetsSPA)
-	fs, err := h.fileServer(h.AssetsWebRoot, h.AssetsLocation, h.AssetsSPA)
+
+	var notFound []byte
+	var err error
+	if h.Assets404 != "" {
+		if notFound, err = os.ReadFile(filepath.Join(h.AssetsLocation, h.Assets404)); err != nil {
+			log.Printf("[WARN] can't read  404 file %s, %v", h.Assets404, err)
+			notFound = nil
+		}
+	}
+
+	log.Printf("[DEBUG] shared assets server enabled for %s %s, spa=%v, not-found=%q",
+		h.AssetsLocation, h.AssetsWebRoot, h.AssetsSPA, h.Assets404)
+
+	fs, err := h.fileServer(h.AssetsWebRoot, h.AssetsLocation, h.AssetsSPA, notFound)
 	if err != nil {
 		log.Printf("[WARN] can't initialize assets server, %v", err)
 		return func(writer http.ResponseWriter, request *http.Request) {}
@@ -336,11 +355,15 @@ func (h *Http) assetsHandler() http.HandlerFunc {
 	return h.CacheControl.Middleware(fs).ServeHTTP
 }
 
-func (h *Http) fileServer(assetsWebRoot, assetsLocation string, spa bool) (http.Handler, error) {
-	if spa {
-		return R.FileServerSPA(assetsWebRoot, assetsLocation, nil)
+func (h *Http) fileServer(assetsWebRoot, assetsLocation string, spa bool, notFound []byte) (http.Handler, error) {
+	var notFoundReader io.Reader
+	if notFound != nil {
+		notFoundReader = bytes.NewReader(notFound)
 	}
-	return R.FileServer(assetsWebRoot, assetsLocation, nil)
+	if spa {
+		return R.FileServerSPA(assetsWebRoot, assetsLocation, notFoundReader)
+	}
+	return R.FileServer(assetsWebRoot, assetsLocation, notFoundReader)
 }
 
 func (h *Http) isAssetRequest(r *http.Request) bool {

app/proxy/proxy_test.go

@@ -189,6 +189,9 @@ func TestHttp_DoWithAssets(t *testing.T) {
 		require.NoError(t, err)
 		defer resp.Body.Close()
 		assert.Equal(t, http.StatusNotFound, resp.StatusCode)
+		body, err := io.ReadAll(resp.Body)
+		require.NoError(t, err)
+		assert.Equal(t, "404 page not found\n", string(body))
 	}
 
 	{
@@ -203,6 +206,85 @@ func TestHttp_DoWithAssets(t *testing.T) {
 	}
 }
 
+func TestHttp_DoWithAssetsCustom404(t *testing.T) {
+	port := rand.Intn(10000) + 40000
+	cc := NewCacheControl(time.Hour * 12)
+	h := Http{Timeouts: Timeouts{ResponseHeader: 200 * time.Millisecond}, Address: fmt.Sprintf("127.0.0.1:%d", port),
+		AccessLog: io.Discard, AssetsWebRoot: "/static", AssetsLocation: "testdata", Assets404: "404.html",
+		CacheControl: cc, Reporter: &ErrorReporter{Nice: false}}
+	ctx, cancel := context.WithTimeout(context.Background(), 1000*time.Millisecond)
+	defer cancel()
+
+	ds := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		t.Logf("req: %v", r)
+		w.Header().Add("h1", "v1")
+		require.Equal(t, "127.0.0.1", r.Header.Get("X-Real-IP"))
+		fmt.Fprintf(w, "response %s", r.URL.String())
+	}))
+
+	svc := discovery.NewService([]discovery.Provider{
+		&provider.Static{Rules: []string{
+			"localhost,^/api/(.*)," + ds.URL + "/123/$1,",
+			"127.0.0.1,^/api/(.*)," + ds.URL + "/567/$1,",
+		},
+		}}, time.Millisecond*10)
+
+	go func() {
+		_ = svc.Run(context.Background())
+	}()
+	time.Sleep(50 * time.Millisecond)
+	h.Matcher = svc
+	h.Metrics = mgmt.NewMetrics()
+
+	go func() {
+		_ = h.Run(ctx)
+	}()
+	time.Sleep(50 * time.Millisecond)
+
+	client := http.Client{}
+
+	{
+		req, err := http.NewRequest("GET", "http://127.0.0.1:"+strconv.Itoa(port)+"/api/something", http.NoBody)
+		require.NoError(t, err)
+		resp, err := client.Do(req)
+		require.NoError(t, err)
+		defer resp.Body.Close()
+		assert.Equal(t, http.StatusOK, resp.StatusCode)
+		t.Logf("%+v", resp.Header)
+
+		body, err := io.ReadAll(resp.Body)
+		require.NoError(t, err)
+		assert.Equal(t, "response /567/something", string(body))
+		assert.Equal(t, "", resp.Header.Get("App-Method"))
+		assert.Equal(t, "v1", resp.Header.Get("h1"))
+	}
+
+	{
+		resp, err := client.Get("http://localhost:" + strconv.Itoa(port) + "/static/1.html")
+		require.NoError(t, err)
+		defer resp.Body.Close()
+		assert.Equal(t, http.StatusOK, resp.StatusCode)
+		t.Logf("%+v", resp.Header)
+
+		body, err := io.ReadAll(resp.Body)
+		require.NoError(t, err)
+		assert.Equal(t, "test html", string(body))
+		assert.Equal(t, "", resp.Header.Get("App-Method"))
+		assert.Equal(t, "", resp.Header.Get("h1"))
+		assert.Equal(t, "public, max-age=43200", resp.Header.Get("Cache-Control"))
+	}
+
+	{
+		resp, err := client.Get("http://localhost:" + strconv.Itoa(port) + "/static/bad.html")
+		require.NoError(t, err)
+		defer resp.Body.Close()
+		assert.Equal(t, http.StatusNotFound, resp.StatusCode)
+		body, err := io.ReadAll(resp.Body)
+		require.NoError(t, err)
+		assert.Equal(t, "not found! blah blah blah\nthere is no spoon", string(body))
+	}
+}
+
 func TestHttp_DoWithSpaAssets(t *testing.T) {
 	port := rand.Intn(10000) + 40000
 	cc := NewCacheControl(time.Hour * 12)

app/proxy/testdata/404.html

@@ -0,0 +1,2 @@
+not found! blah blah blah
+there is no spoon