Previously, when request body was not available or was previously read in memory rather than a file, client received HTTP 500 error, but no explanation was logged in error log. This could happen, for example, if request body was read or discarded prior to error_page redirect, or if mirroring was enabled along with dav.
If the flag space_in_uri is set, the URI in HTTP upstream request is escaped to convert space to %20. However this flag is not checked while creating the default cache key. This leads to different cache keys for requests '/foo bar' and '/foo%20bar', while the upstream requests are identical. Additionally, the change fixes background cache updates when the client URI contains unescaped space. Default cache key in a subrequest is always based on escaped URI, while the main request may not escape it. As a result, background cache update subrequest may update a different cache entry.
Previously, the unparsed uri was explicitly allowed to be used only by the main request. However the valid_unparsed_uri flag is nonzero only in the main request, which makes the main request check pointless.
If a connection with the read delayed flag set was stored in the keepalive cache, and after picking it from the cache a read timer was set on that connection, this timer was considered a delay timer rather than a socket read event timer as expected. The latter timeout is usually much longer than the former, which caused a significant delay in request processing. The issue manifested itself with proxy_limit_rate and upstream keepalive enabled and exists since 973ee2276300 (1.7.7) when proxy_limit_rate was introduced.
A zlib variant from Intel as available from https://github.com/jtkukunas/zlib uses 64K hash instead of scaling it from the specified memory level, and also uses 16-byte padding in one of the window-sized memory buffers, and can force window bits to 13 if compression level is set to 1 and appropriate compile options are used. As a result, nginx complained with "gzip filter failed to use preallocated memory" alerts. This change improves deflate_state allocation detection by testing that items is 1 (deflate_state is the only allocation where items is 1). Additionally, on first failure to use preallocated memory we now assume that we are working with the Intel's modified zlib, and switch to using appropriate preallocations. If this does not help, we complain with the usual alerts. Previous version of this patch was published at http://mailman.nginx.org/pipermail/nginx/2014-July/044568.html. The zlib variant in question is used by default in ClearLinux from Intel, see http://mailman.nginx.org/pipermail/nginx-ru/2017-October/060421.html, http://mailman.nginx.org/pipermail/nginx-ru/2017-November/060544.html.
If parameters were specified in xslt_stylesheet without variables, any request except the first would cause an internal server error.
Previously, nginx failed to move buffer position when parsing an incomplete record header, and due to this wasn't be able to continue parsing once remaining bytes of the record header were received. This can affect response header parsing, potentially generating spurious errors like "upstream sent unexpected FastCGI request id high byte: 1 while reading response header from upstream". While this is very unlikely, since usually record headers are written in a single buffer, this still can happen in real life, for example, if a record header will be split across two TCP packets and the second packet will be delayed. This does not affect non-buffered response body proxying, due to "buf->pos = buf->last;" at the start of the ngx_http_fastcgi_non_buffered_filter() function. Also this does not affect buffered response body proxying, as each input buffer is only passed to the filter once.