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indexer: add Accept-Encoding aware middleware
This commit adds a middleware that examines the incoming "accept-encoding" header and attempt to compress the payload accordingly, and sets the `clair` binary to use it automatically.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,151 @@ | ||
| package main | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "io" | ||
| "net/http" | ||
| "sync" | ||
|
|
||
| "github.com/klauspost/compress/flate" | ||
| "github.com/klauspost/compress/gzip" | ||
| "github.com/klauspost/compress/snappy" | ||
| "github.com/markusthoemmes/goautoneg" | ||
| ) | ||
|
|
||
| // Compress wraps the provided http.Handler and provides transparent body | ||
| // compression based on a Request's "Accept-Encoding" header. | ||
| func Compress(next http.Handler) http.Handler { | ||
| h := compressHandler{ | ||
| next: next, | ||
| } | ||
| h.snappy.New = func() interface{} { | ||
| return snappy.NewBufferedWriter(nil) | ||
| } | ||
| h.gzip.New = func() interface{} { | ||
| w, _ := gzip.NewWriterLevel(nil, gzip.BestSpeed) | ||
| return w | ||
| } | ||
| h.flate.New = func() interface{} { | ||
| w, _ := flate.NewWriter(nil, flate.BestSpeed) | ||
| return w | ||
| } | ||
|
|
||
| return &h | ||
| } | ||
|
|
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| var _ http.Handler = (*compressHandler)(nil) | ||
|
|
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| // CompressHandler performs transparent HTTP body compression. | ||
| type compressHandler struct { | ||
| snappy, gzip, flate sync.Pool | ||
| next http.Handler | ||
| } | ||
|
|
||
| // Header is an interface that has the http.ResponseWriter's Header-related | ||
| // methods. | ||
| type header interface { | ||
| Header() http.Header | ||
| WriteHeader(int) | ||
| } | ||
|
|
||
| // ServeHTTP implements http.Handler. | ||
| func (c *compressHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) { | ||
| var ( | ||
| flusher http.Flusher | ||
| pusher http.Pusher | ||
| cw io.WriteCloser | ||
| ) | ||
| flusher, _ = w.(http.Flusher) | ||
| pusher, _ = w.(http.Pusher) | ||
|
|
||
| // Find the first accept-encoding we support. | ||
| for _, a := range goautoneg.ParseAccept(r.Header.Get("accept-encoding")) { | ||
| switch a.Type { | ||
| case "gzip": | ||
| w.Header().Set("content-encoding", "gzip") | ||
| gz := c.gzip.Get().(*gzip.Writer) | ||
| defer c.gzip.Put(gz) | ||
| cw = gz | ||
| case "deflate": | ||
| w.Header().Set("content-encoding", "deflate") | ||
| z := c.flate.Get().(*flate.Writer) | ||
| defer c.flate.Put(z) | ||
| cw = z | ||
| case "snappy": // Nonstandard | ||
| w.Header().Set("content-encoding", "snappy") | ||
| s := c.snappy.Get().(*snappy.Writer) | ||
| defer c.snappy.Put(s) | ||
| cw = s | ||
| case "identity": | ||
| w.Header().Set("content-encoding", "identity") | ||
| case "*": | ||
| default: | ||
| continue | ||
| } | ||
| break | ||
| } | ||
| // Do some setup so we can see the error, albeit as a trailer. | ||
| if cw != nil { | ||
| const errHeader = `clair-error` | ||
| w.Header().Add("trailer", errHeader) | ||
| defer func() { | ||
| if err := cw.Close(); err != nil { | ||
| w.Header().Add(errHeader, err.Error()) | ||
| } | ||
| }() | ||
| } | ||
|
|
||
| // Nw is the http.ResponseWriter for our next http.Handler. | ||
| var nw http.ResponseWriter | ||
| // This is a giant truth table to make anonymous types that satisfy as many | ||
| // optional interfaces as possible. | ||
| // | ||
| // We care about 3 interfaces, so there are 2^3 == 8 combinations | ||
| switch { | ||
| case flusher == nil && pusher == nil && cw == nil: | ||
| nw = w | ||
| case flusher == nil && pusher == nil && cw != nil: | ||
| nw = struct { | ||
| header | ||
| io.Writer | ||
| }{w, cw} | ||
| case flusher == nil && pusher != nil && cw == nil: | ||
| nw = struct { | ||
| http.ResponseWriter | ||
| http.Pusher | ||
| }{w, pusher} | ||
| case flusher == nil && pusher != nil && cw != nil: | ||
| nw = struct { | ||
| header | ||
| io.Writer | ||
| http.Pusher | ||
| }{w, cw, pusher} | ||
| case flusher != nil && pusher == nil && cw == nil: | ||
| nw = struct { | ||
| http.ResponseWriter | ||
| http.Flusher | ||
| }{w, flusher} | ||
| case flusher != nil && pusher == nil && cw != nil: | ||
| nw = struct { | ||
| header | ||
| io.Writer | ||
| http.Flusher | ||
| }{w, cw, flusher} | ||
| case flusher != nil && pusher != nil && cw == nil: | ||
| nw = struct { | ||
| http.ResponseWriter | ||
| http.Flusher | ||
| http.Pusher | ||
| }{w, flusher, pusher} | ||
| case flusher != nil && pusher != nil && cw != nil: | ||
| nw = struct { | ||
| header | ||
| io.Writer | ||
| http.Flusher | ||
| http.Pusher | ||
| }{w, cw, flusher, pusher} | ||
| default: | ||
| panic(fmt.Sprintf("unexpect type combination: %T/%T/%T", flusher, pusher, cw)) | ||
| } | ||
| c.next.ServeHTTP(nw, r) | ||
| } |
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