Merging r4151, r4152, r4177: HTTP cache related fixes: *) Cache: fix for sending of empty responses. Revert wrong fix for empty responses introduced in 0.8.31 and apply new one, rewritten to match things done by static module as close as possible. *) Cache: fix for sending of stale responses. For normal cached responses ngx_http_cache_send() sends last buffer and then request finalized via ngx_http_finalize_request() call, i.e. everything is ok. But for stale responses (i.e. when upstream died, but we have something in cache) the same ngx_http_cache_send() sends last buffer, but then in ngx_http_upstream_finalize_request() another last buffer is send. This causes duplicate final chunk to appear if chunked encoding is used (and resulting problems with keepalive connections and so on). Fix this by not sending in ngx_http_upstream_finalize_request() another last buffer if we know response was from cache. *) Fixed cache bypass caching of non-cacheable replies (ticket #21). If cache was bypassed with proxy_cache_bypass, cache-controlling headers (Cache-Control, Expires) wasn't considered and response was cached even if it was actually non-cacheable. Patch by John Ferlito.