Le 13/02/2019 à 09:34, Laurent Penot a écrit :
Hi Thierry, guys,
When receiving a POST request on haproxy, I use lua to compute some
values, and modify the body of the request before forwarding to the
backend, so my backend can get these variables from the POST and use them.
Here is a sample cfg, and lua code to reproduce this.
##### Conf (I removed all defauts, timeout and co ..) :
frontend front-nodes
bind :80
# option to wait for the body before processing (mandatory for POST
requests)
option http-buffer-request
# default backend
default_backend be_test
http-request lua.manageRequests
##### Lua :
*function */manageRequests/(txn)
-- create new postdata
*local *newPostData = /core/./concat/()
newPostData:add('POST /test.php HTTP/1.1\r\n')
newPostData:add('Host: test1\r\n')
newPostData:add('content-type: application/x-www-form-urlencoded\r\n')
*local *newBodyStr = 'var1=valueA&var2=valueB'
*local *newBodyLen = string.len(newBodyStr)
newPostData:add('content-length: ' .. tostring(newBodyLen) .. '\r\n')
newPostData:add('\r\n')
newPostData:add(newBodyStr)
*local *newPostDataStr = tostring(newPostData:dump())
txn.req:send(newPostDataStr)
*end*
/core/./register_action/("manageRequests", { "http-req" }, /manageRequests/)
This is working well in haproxy 1.8.x (x : 14 to 18) but I get the
following error with 1.9.4 (same error with 1.9.2, others 1.9.x versions
not tested) :
Lua function 'manageRequests': runtime error: 0 from [C] method 'send',
/etc/haproxy/lua/bench.lua:97 C function line 80.
Line 97 of my lua file is txn.req:send(newPostDataStr)
Maybe I’m missing something on 1.9.x but cant find what, or maybe it’s a
bug, I can’t say.
Hi Laurent,
It is not supported to modify an HTTP request/response calling Channel
functions. It means calling following functions within an HTTP proxy is
forbidden: Channel.get, Channel.dup, Channel.getline, Channel.set,
Channel.append, Channel.send, Channel.forward.
Since HAProxy 1.9, a runtime error is triggered (because there is no way
to do it during the configuration parsing, AFAIK). You may see this as a
regression, but in fact, it was never really supported. But because of a
lack check, no error was triggered. Because these functions totally
hijacked the HTTP parser, if used, the result is undefined. There are
many ways to crash HAProxy. Unfortunately, for now, there is no way to
rewrite the HTTP messages in Lua.
--
Christopher Faulet
