Instead of compressing all chunks as they come, we store them in a temporary
buffer. The compression happens during the forwarding phase. This change speeds
up the compression of chunked response.
Before, functions to filter HTTP body (and TCP data) were called from the moment
at least one filter was attached to the stream. If no filter is interested by
these data, this uselessly slows data parsing.
A good example is the HTTP compression filter. Depending of request and response
headers, the response compression can be enabled or not. So it could be really
nice to call it only when enabled.
So, now, to filter HTTP/TCP data, a filter must use the function
register_data_filter. For TCP streams, this function can be called only
once. But for HTTP streams, when needed, it must be called for each HTTP request
or HTTP response.
Only registered filters will be called during data parsing. At any time, a
filter can be unregistered by calling the function unregister_data_filter.
From the stream point of view, this new structure is opaque. it hides filters
implementation details. So, impact for future optimizations will be reduced
(well, we hope so...).
Some small improvements has been made in filters.c to avoid useless checks.
This new analyzer will be called for each HTTP request/response, before the
parsing of the body. It is identified by AN_FLT_HTTP_HDRS.
Special care was taken about the following condition :
* the frontend is a TCP proxy
* filters are defined in the frontend section
* the selected backend is a HTTP proxy
So, this patch explicitly add AN_FLT_HTTP_HDRS analyzer on the request and the
response channels when the backend is a HTTP proxy and when there are filters
attatched on the stream.
This patch simplifies http_request_forward_body and http_response_forward_body
functions.
For Chunked HTTP request/response, the body filtering can be really
expensive. In the worse case (many chunks of 1 bytes), the filters overhead is
of 3 calls per chunk. If http_data callback is useful, others are just
informative.
So these callbacks has been removed. Of course, existing filters (trace and
compression) has beeen updated accordingly. For the HTTP compression filter, the
update is quite huge. Its implementation is closer to the old one.
HTTP compression has been rewritten to use the filter API. This is more a PoC
than other thing for now. It allocates memory to work. So, if only for that, it
should be rewritten.
In the mean time, the implementation has been refactored to allow its use with
other filters. However, there are limitations that should be respected:
- No filter placed after the compression one is allowed to change input data
(in 'http_data' callback).
- No filter placed before the compression one is allowed to change forwarded
data (in 'http_forward_data' callback).
For now, these limitations are informal, so you should be careful when you use
several filters.
About the configuration, 'compression' keywords are still supported and must be
used to configure the HTTP compression behavior. In absence of a 'filter' line
for the compression filter, it is added in the filter chain when the first
compression' line is parsed. This is an easy way to do when you do not use other
filters. But another filter exists, an error is reported so that the user must
explicitly declare the filter.
For example:
listen tst
...
compression algo gzip
compression offload
...
filter flt_1
filter compression
filter flt_2
...
HTTP compression will be moved in a true filter. To prepare the ground, some
functions have been moved in a dedicated file. Idea is to keep everything about
compression algos in compression.c and everything related to the filtering in
flt_http_comp.c.
For now, a header has been added to help during the transition. It will be
removed later.
Unused empty ACL keyword list was removed. The "compression" keyword
parser was moved from cfgparse.c to flt_http_comp.c.
