from django.utils.cache import patch_vary_headers from django.utils.deprecation import MiddlewareMixin from django.utils.regex_helper import _lazy_re_compile from django.utils.text import compress_sequence, compress_string re_accepts_gzip = _lazy_re_compile(r'\bgzip\b') class GZipMiddleware(MiddlewareMixin): """ Compress content if the browser allows gzip compression. Set the Vary header accordingly, so that caches will base their storage on the Accept-Encoding header. """ def process_response(self, request, response): # It's not worth attempting to compress really short responses. if not response.streaming and len(response.content) < 200: return response # Avoid gzipping if we've already got a content-encoding. if response.has_header('Content-Encoding'): return response patch_vary_headers(response, ('Accept-Encoding',)) ae = request.META.get('HTTP_ACCEPT_ENCODING', '') if not re_accepts_gzip.search(ae): return response if response.streaming: # Delete the `Content-Length` header for streaming content, because # we won't know the compressed size until we stream it. response.streaming_content = compress_sequence(response.streaming_content) del response['Content-Length'] else: # Return the compressed content only if it's actually shorter. compressed_content = compress_string(response.content) if len(compressed_content) >= len(response.content): return response response.content = compressed_content response['Content-Length'] = str(len(response.content)) # If there is a strong ETag, make it weak to fulfill the requirements # of RFC 7232 section-2.1 while also allowing conditional request # matches on ETags. etag = response.get('ETag') if etag and etag.startswith('"'): response['ETag'] = 'W/' + etag response['Content-Encoding'] = 'gzip' return response