prometheus/web/blob/blob.go

package blob

import (
	"bytes"
	"compress/gzip"
	"fmt"
	"io"
	"net/http"
	"strings"

	"github.com/prometheus/log"
)

// Sub-directories for templates and static content.
const (
	TemplateFiles = "templates"
	StaticFiles   = "static"
)

var mimeMap = map[string]string{
	"css":        "text/css",
	"js":         "text/javascript",
	"descriptor": "application/vnd.google.protobuf;proto=google.protobuf.FileDescriptorSet",
}

// GetFile retrieves the content of an embedded file.
func GetFile(bucket string, name string) ([]byte, error) {
	blob, ok := files[bucket][name]
	if !ok {
		return nil, fmt.Errorf("could not find %s/%s (missing or updated files.go?)", bucket, name)
	}
	reader := bytes.NewReader(blob)
	gz, err := gzip.NewReader(reader)
	if err != nil {
		return nil, err
	}

	var b bytes.Buffer
	io.Copy(&b, gz)
	gz.Close()

	return b.Bytes(), nil
}

// Handler implements http.Handler.
type Handler struct{}

func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	name := r.URL.Path
	if name == "" {
		name = "index.html"
	}

	file, err := GetFile(StaticFiles, name)
	if err != nil {
		if err != io.EOF {
			log.Warn("Could not get file: ", err)
		}
		w.WriteHeader(http.StatusNotFound)
		return
	}
	contentType := http.DetectContentType(file)
	if strings.Contains(contentType, "text/plain") || strings.Contains(contentType, "application/octet-stream") {
		parts := strings.Split(name, ".")
		contentType = mimeMap[parts[len(parts)-1]]
	}
	w.Header().Set("Content-Type", contentType)
	w.Header().Set("Cache-Control", "public, max-age=259200")
	w.Write(file)
}