CODEWITHSUNDEEP
luahaproxy
RootOfProblem
RootOfProblem

Reputation: 377

lua script execution in haproxy throws "yield not allowed"

i want to loadbalance soap requests between coming from a client to different instances of my service. i cant change the client and want to make the requests sticky by looking in to the payload of the requests and extracting a certain id, to make sure all requests with the same id end up on the same instance.

i've wrote a lua script to look into the payload and extra Information i Need. But for some reason every 5-6th requests has 50-60ms latency to establish Connection (the requests in between have 0ms latency) and i see log entry like 

Oct 15 23:27:48 rp-proxy-p1 haproxy[30995]: Lua sample-fetch 'parseElement': yield not allowed.
Oct 15 23:27:48 rp-proxy-p1 haproxy[30995]: Lua sample-fetch 'parseElement': yield not allowed.

How can i prevent this latency and avoid the errors to occur and what does it mean?

my haproxy.cfg

global
    log /dev/log    local0
    log /dev/log    local1 notice
    chroot /var/lib/haproxy
    stats socket /run/haproxy/admin.sock mode 660 level admin
    stats timeout 30s
    user haproxy
    group haproxy
    daemon

    lua-load /etc/haproxy/routing.lua

defaults
    log global
    mode tcp
    option tcplog
    option dontlognull
    retries 3
    option redispatch
    maxconn 2000
    timeout connect 1000
    timeout client  500000
    timeout server  500000

frontend my_frontend
    bind *:7001
    default_backend my_backend

backend my_backend
    option tcp-check 
    balance source
    stick-table type string size 30000k expire 30m
    stick on "lua.parseElement" 
    server  server1  server1.domain.com:8080 check port 8080 weight 1
    server  server2  server2.domain.com:8080 check port 8080 weight 1

routing.lua

 function parseElement(txn, salt)

    local payload = txn.req:dup()
    local trx_id = payload.match(payload, "<transaction_id>(.-)</transaction_id>")
    core.Info("value: "..trx_id)
    return trx_id
end

core.register_fetches("parseElement", parseElement)

Upvotes: 0

Views: 1095

Answers (1)

RootOfProblem
RootOfProblem

Reputation: 377

actually i just found the fault in my configuration.

1st) the backend should run in http mode, therefor i added mode http to backend my_backend

2nd) the lua script tries to access the body (txn.req) but can't when the Body has not yet arrived when the script is executed. you can force haproxy to wait for the body to arrive before the script is executed by adding option http-buffer-request to backend my_backend

backend my_backend
    mode http
    option http-buffer-request
    option tcp-check 
    balance source
    stick-table type string size 30000k expire 30m
    stick on "lua.parseElement" 
    server  server1  server1.domain.com:8080 check port 8080 weight 1
    server  server2  server2.domain.com:8080 check port 8080 weight 1

Upvotes: 1

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