DecompressionHandler.md

Decompression Handler

A middleware component that requests, detects and decompresses response bodies.

Requirements

• Add Accept-encoding: gzip to request headers.
• Decompress response bodies that have the header Content-Encoding: gzip
• Compression handler should be installed as a default handler by GraphClientFactory
• Additional observability requirements in Observability

Remarks

For request payload compression, refer to the compression handler specification.

State of automatic decompression

The following table describes the state of automatic decompression of responses. When automatic decompression is supported, we don't need to implement it manually.

Language	Client	Automatic decompression	Source	Notes
CSharp	HttpClient	Yes	link	Only if the handler AutomaticDecompression is set to All (not the default!)
Go	net/http	Yes	link	Only gzip is supported. Ensure DisableCompression is false (default) on the transport.
Java	OkHttp	Yes	link
PHP	Guzzle	Yes	link	Does NOT add the accept encoding header automatically.
Python	HTTPX	Yes	None	Couldn't find any source, but tested with 0.27.0 and httpbin
TypeScript/JavaScript	fetch	Yes	link	Automatically adds the accept encoding header and decompresses the response. Make sure compress is set to true (default) in the request options.

Example

    public class DecompressionHandler : DelegatingHandler
    {
        protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            // Declare compression support to server
            var gzipQString = new StringWithQualityHeaderValue("gzip");
            if (!request.Headers.AcceptEncoding.Contains(gzipQString))
            {
                request.Headers.AcceptEncoding.Add(gzipQString);
            }

            // Record feature usage for telemetry
            var requestContext = request.GetRequestContext();
            requestContext.FeatureUsage |= FeatureFlag.CompressionHandler;

            // Send Request
            var response = await base.SendAsync(request, cancellationToken);

            // Decompress gzipped responses
            if (response.Content != null && response.Content.Headers.ContentEncoding.Contains("gzip"))
            {
                response.Content = new StreamContent(new GZipStream(await response.Content.ReadAsStreamAsync(), CompressionMode.Decompress));
            }
            return response;
        }
    }