Hi all,
Is it at all feasible to modify a TCP payload via a custom LUA action
in a stable manner? ie, something like this;
function enrich_query(txn)
--- Duplicate request. :set() will replace the request, if possible
local req = txn.req:dup()
-- if error or client closes connection, quit
if req == nil then return end
--- Add an identifier for haproxy and include client's IP address.
if txn.req:set("-Vha1.8," .. txn.f:src() .. " " .. req) == -1 then
txn.Error(txn, "Failed to enrich query")
end
end
core.register_action('enrich_query', {'tcp-req'}, enrich_query)
Then called as an action in the frontend;
# Don't enrich if query already contains client identification
acl has_client_version req.payload(0,0) -m sub -- -V --client
# Enrich our query
tcp-request content lua.enrich_query if !has_client_version
WAIT_END
The reason I ask is that I randomly get yield errors, I assume during
the txn.req:set() ;
Lua function 'enrich_query': yield not allowed.
I have experimented with different values of tune.lua.forced-yield with
little success. Sometimes this occurs very infrequently, other times,
very frequently.
FYI - I have experimented with PROXY, but our backend application is
using a java API that doesn't have native PROXY support (although
there's been a patch pending for about 5 years). Have also experimented
with PROXY and Cloudflare's "mmproxy". That works well, but i've been
asked to use LUA to extend haproxy if possible.
Thanks,
Grant
