kataras/iris · info

compress: request is not compressed

Error message

compress: request is not compressed

What it means

ErrRequestNotCompressed is returned by NewCompressReader when an incoming request is not actually compressed. The caller attempted to create a decompression reader for the request body, but the request's Content-Encoding header indicates no compression. It is a sentinel used to fall back to reading the body as-is.

Source

Thrown at context/compress.go:36

const (
	GZIP    = "gzip"
	DEFLATE = "deflate"
	BROTLI  = "br"
	SNAPPY  = "snappy"
	S2      = "s2"
)

// IDENTITY no transformation whatsoever.
const IDENTITY = "identity"

var (
	// ErrResponseNotCompressed returned from AcquireCompressResponseWriter
	// when response's Content-Type header is missing due to golang/go/issues/31753 or
	// when accept-encoding is empty. The caller should fallback to the original response writer.
	ErrResponseNotCompressed = errors.New("compress: response will not be compressed")
	// ErrRequestNotCompressed returned from NewCompressReader
	// when request is not compressed.
	ErrRequestNotCompressed = errors.New("compress: request is not compressed")
	// ErrNotSupportedCompression returned from
	// AcquireCompressResponseWriter, NewCompressWriter and NewCompressReader
	// when the request's Accept-Encoding was not found in the server's supported
	// compression algorithms. Check that error with `errors.Is`.
	ErrNotSupportedCompression = errors.New("compress: unsupported compression")
)

// AllEncodings is a slice of default content encodings.
// See `AcquireCompressResponseWriter`.
var AllEncodings = []string{GZIP, DEFLATE, BROTLI, SNAPPY}

// GetEncoding extracts the best available encoding from the request.
func GetEncoding(r *http.Request, offers []string) (string, error) {
	acceptEncoding := r.Header[AcceptEncodingHeaderKey]

	if len(acceptEncoding) == 0 {
		return "", ErrResponseNotCompressed
	}

View on GitHub (pinned to 7bedaf55a0)

Solutions

1. Check the request's Content-Encoding header before creating the reader and only call NewCompressReader when it names a supported encoding.
2. Handle the sentinel with errors.Is(err, iris.ErrRequestNotCompressed) and read the body uncompressed (ctx.Request().Body).
3. Fix the sending client to set Content-Encoding (e.g. Content-Encoding: gzip) when it actually compresses the body.
4. Verify no proxy/load balancer is stripping Content-Encoding from incoming requests.

Example fix

// before
r, err := ctx.DecompressReader()
if err != nil { ctx.StopWithStatus(500); return }
// after
r, err := ctx.DecompressReader()
if err != nil {
    if errors.Is(err, iris.ErrRequestNotCompressed) {
        r = ctx.Request().Body // read uncompressed body as-is
    } else {
        ctx.StopWithStatus(500)
        return
    }
}

contentEncoding := ctx.GetHeader("Content-Encoding")
if contentEncoding == "" || contentEncoding == "identity" {
    // request body is not compressed; read it directly
}

func isCompressedRequest(r *http.Request) bool {
    ce := r.Header.Get("Content-Encoding")
    return ce != "" && ce != "identity"
}

r, err := ctx.DecompressReader()
if err != nil {
    if errors.Is(err, iris.ErrRequestNotCompressed) {
        r = ctx.Request().Body // read body uncompressed
    } else {
        ctx.StopWithStatus(iris.StatusInternalServerError)
        return
    }
}

When it happens

Trigger: Calling NewCompressReader (e.g. via ctx.DecompressReader or compression middleware reading the body) when the request's Content-Encoding header is missing, empty, or set to "identity".

Common situations: A client uploads an uncompressed body while the server unconditionally wraps the body in a decompress reader; misconfigured API clients that forget Content-Encoding: gzip; load balancers or proxies that decompress request bodies upstream and strip the Content-Encoding header.

Related errors

• compress: response will not be compressed
• compress: unsupported compression
• ErrNotSupportedCompression
• empty form
• empty form field

AI-assisted analysis of kataras/iris@7bedaf55a0 (2026-08-30). Data as JSON: /api/errors/f8943c829609894b. Report an issue: GitHub.