bad request on repeated requests

[r614]

hi! i am running into the following error when my openresty/nginx server gets repeated requests to an endpoint.
after a certain point, all requests start failing with:

2022/07/05 22:32:21 [error] 7#7: *24332 lua entry thread aborted: runtime error: /usr/local/openresty/luajit/share/lua/5.1/pgmoon/init.lua:251: bad request
stack traceback:
coroutine 0:
	[C]: in function 'connect'
	/usr/local/openresty/luajit/share/lua/5.1/pgmoon/init.lua:251: in function 'connect'
	/usr/local/openresty/nginx//rewrite.lua:66: in function 'connect'
	/usr/local/openresty/nginx//rewrite.lua:92: in function 'pod_data_by_id'
	/usr/local/openresty/nginx//rewrite.lua:132: in function 'go'
	rewrite_by_lua(nginx.conf:45):2: in main chunk, client: <ip>, server: , request: "GET /?auth-token=<some_token>HTTP/1.1", host: <some host>

it's failing when calling the connect function on a request:

local _pg_cfg = pgmoon.new({
  host = os.getenv("pg_host"),
  port = os.getenv("pg_port"),
  user = os.getenv("pg_user"),
  database = os.getenv("pg_db"),
  password = os.getenv("pg_pw")
})


local connect = function()
  local success, err = _pg_cfg:connect()
  if err ~= nil then
    ngx.log(ngx.ERR, err)
    ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
  end
  if not success then
    ngx.log(ngx.ERR, "Could not acquire a Postgres connection")
    ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
  end
  return _pg_cfg
end

[leafo]

I'm not entirely sure since there are many factors about your setup that could influence what's going on, but based on the error message it sounds like you're trying to issue commands to the server on a connection socket that is in a different state and expecting something else. Eg. send sending connect protocol messages through a socket that has already established a connection to the database

[r614]

thanks for the response! i managed to fix it by moving the _pg_cfg block inside the connect function, something like this:

local connect = function()
 local _pg_cfg = pgmoon.new({
   host = os.getenv("pg_host"),
   port = os.getenv("pg_port"),
   user = os.getenv("pg_user"),
   database = os.getenv("pg_db"),
   password = os.getenv("pg_pw")
 })
 local success, err = _pg_cfg:connect()
 if err ~= nil then
   ngx.log(ngx.ERR, err)
   ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
 end
 if not success then
   ngx.log(ngx.ERR, "Could not acquire a Postgres connection")
   ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
 end
 return _pg_cfg
end

to be honest, i am not sure why this fixed the issue. my guess was similar that there's a state mismatch, but beyond that, i have no clue since this was also my first time messing around with nginx + lua lol.

[leafo]

The object returned by pgmoon.new is a stateful object that holds the connection socket. Based on what you said it sounds like you were attempting to re-use it for a new connection by calling pg:connect without closing the existing connection that would have been opened on a previous call to your connect function.

Your solution of creating a new instance on every new connection is perfectly fine and my recommended approach. The previous connection will automatically be closed via garbage collection if you don't explicitly close it. I recommend this approach since if you are/ever use threading via coroutines you want each thread to have its own connection since query functions are not atomic (eg. commonly lua async network libraries yield on any network activity, and the connection may be in the middle of sending a receiving a query when a new thread is yielded to)