Dynamic URL for proxy_pass directive via lua_module

mobyrish

Hi all !

The requirement is to use the dynamic URL for proxy_pass directive . By using $arg_name built variable and lua code(openresty) , query parameter value acts as KEY to retrieve the corresponding VALUE ( target URL for proxy_pass directive) stored in Redis. For example in the URL http://10.10.10.3/?cust=cust2 , $arg_cust gets cust2 as KEY which is further used to retrieve corresponding VALUE stored in Redis .

It works fine for all the target url BUT one the target URL returns error when KEY value from the uri is retrieved dynamically via $arg_cust (http://10.10.10.3/?cust=cust2). curl http://10.10.10.3/?cust=cust2 works OK. Interesting to note is that if KEY value (cust2) is hard-coded in lua , it also works OK.

The target URL gets appended with extended new URL path in upstream server (this part "/common/NSLogin.jsp?redirect=/console" gets added ) via embeded _javascript_ in the index page. I do not understand WHY it works when KEY value (cust2) is hard coded in the lua but does not work if same KEY value (cust2) is retrieved via $arg_cust variable. As I said earlier, all other URL works fine for $arg_cust EXCEPT above one . May be error is due to extended URL in up-stream server. Here is my code

######################################## server block code ###############################################################

server {

listen 80;

server_name localhost;

set $ngcust $arg_cust; # <<<<< NOT WORKING

#set $ngcust "cust2"; # <<<<< Works OK if commented-out.

set $ng1 ' ';

location / {

access_by_lua_block {

local key = ngx.var.ngcust

local redis = require "resty.redis"

local red = redis:new()

red:set_timeout(1000) -- 1 sec

local ok, err = red:connect("127.0.0.1", 6379)

if not ok then

ngx.say("failed to connect: ", err)

return

end

local res, err = red:get(key)

ngx.var.ng1=res

-- ngx.say(ngx.var.ng1) <<<<<<<<< also shows correct VALUE retrieved from Redis.

}

proxy_set_header HOST $host;

proxy_set_header X-Forwarded-Proto $scheme;

proxy_set_header X-Real-IP $remote_addr;

proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

proxy_pass "http://$ng1";

}

###############################################################################

#########error.log#######################

access_by_lua(nginx.conf:72):16: in function <access_by_lua(nginx.conf:72):1>, client: 10.10.10.1, server: localhost, request: "GET /favicon.ico HTTP/1.1", host: "10.10.10.3", referrer: "http://10.10.10.3/common/NSLogin.jsp?redirect=/console"

2017/10/12 17:45:17 [notice] 3076#3076: signal process started

2017/10/12 17:45:17 [notice] 6086#6086: signal 1 (SIGHUP) received, reconfiguring

2017/10/12 17:45:17 [notice] 6086#6086: reconfiguring

2017/10/12 17:45:17 [notice] 6086#6086: using the "epoll" event method

2017/10/12 17:45:17 [notice] 6086#6086: start worker processes

2017/10/12 17:45:17 [notice] 6086#6086: start worker process 3077

2017/10/12 17:45:17 [notice] 2748#2748: gracefully shutting down

2017/10/12 17:45:17 [notice] 2748#2748: exiting

2017/10/12 17:45:17 [notice] 2748#2748: exit

2017/10/12 17:45:17 [notice] 6086#6086: signal 17 (SIGCHLD) received

2017/10/12 17:45:17 [notice] 6086#6086: worker process 2748 exited with code 0

2017/10/12 17:45:17 [notice] 6086#6086: signal 29 (SIGIO) received

2017/10/12 17:46:00 [error] 3077#3077: *31502 lua entry thread aborted: runtime error: access_by_lua(nginx.conf:72):16: bad argument #1 to '__newindex' (string, number, or nil expected, but got userdata)

stack traceback:

coroutine 0:

[C]: in function '__newindex'

stack traceback:

coroutine 0:

[C]: in function '__newindex'

stack traceback:

coroutine 0:

[C]: in function '__newindex'

2017/10/12 17:46:00 [error] 3077#3077: *31503 lua entry thread aborted: runtime error: access_by_lua(nginx.conf:72):16: bad argument #1 to '__newindex' (string, number, or nil expected, but got userdata)

stack traceback:

coroutine 0:

[C]: in function '__newindex'

access_by_lua(nginx.conf:72):16: in function <access_by_lua(nginx.conf:72):1>, client: 10.10.10.1, server: localhost, request: "GET /common/NSLogin.jsp?redirect=/console HTTP/1.1", host: "10.10.10.3", referrer: "http://10.10.10.3/?cust=cust2"

stack traceback:

coroutine 0:

[C]: in function '__newindex'

stack traceback:

coroutine 0:

[C]: in function '__newindex'

2017/10/12 17:46:00 [error] 3077#3077: *31508 lua entry thread aborted: runtime error: access_by_lua(nginx.conf:72):16: bad argument #1 to '__newindex' (string, number, or nil expected, but got userdata)

stack traceback:

coroutine 0:

[C]: in function '__newindex'

stack traceback:

coroutine 0:

[C]: in function '__newindex'

stack traceback:

coroutine 0:

[C]: in function '__newindex'

#######################################################################################################

curl command output .. OK

[root@localhost ~]# curl 10.10.10.3/?cust=cust2

<!DOCTYPE html>

<html>

<head>

<title>nGenius Redirect</title>

function launchSplash()

{

var newPath = "/common/NSLogin.jsp?redirect=/console";

var host = document.location.host;

var protocol = document.location.protocol + "//";

var splashURL = protocol + host + newPath;

return splashURL;

}

var website = launchSplash();

window.location = website;

</script>

</head>

<body>

</body>

</html>

#############################################################

Contents of web-page

An error occurred.

mobyrish · 2017-10-13T05:58:30+00:00

@tokers THANKS ... I somehow missed finding lua-resty-lock :)always better to use something established and tested than to build your ownOn Saturday, October...

Sorry, the page you are looking for is currently unavailable.
Please try again later.

If you are the system administrator of this resource then you should check the error log for details.

Faithfully yours, OpenResty.

zchao1995

Hi!

There is an assignment that the value is got from redis(res), you should check the type since userdata is not accpeted for ngx.var.VARIABLE.

mobyrish

Hi tokers

Thanks for your reply. Let me explain the scenarios

scenario 1. (not working )

local res, err = red:get(key)

In above statement, the value for key parameter comes from uri part ( 10.10.10.3/?cust=cust2 ) by using built-in variable $arg_cust which gets "cust2" for key parameter . The value retrieved against key "cust2" from the Redis is just target URL for proxy_pass.

scenario 2. (working)

But if the key parameter in the above statement is hardcoded with a value like this

local res,err = red:get("cust2") then it works fine.

Findings

1. Scenario 1 works fine with all other target URL of proxy_pass for cust3 , cust4 and so on ( 10.10.10.3/?cust=cust3 ) . The difference is that in case of cust2, the target URL gets appended with extended new URL path in upstream server (this part "/common/NSLogin.jsp?redirect=/console" gets added ) via embeded _javascript_ in the index page .

2. This means lua code encounters an error when the browser gets extended url as added by target upstream.And this happens ONLY when key

value retrieved dynamically via $arg_cust . local res, err = red:get(key)

Any input will be highly appreciated .

On Friday, 13 October 2017 02:46:07 UTC+1, tokers wrote:

Hi!

There is an assignment that the value is got from redis(res), you should check the type since userdata is not accpeted for ngx.var.VARIABLE.

mobyrish

Just to say that I get same error for all target URL irrespective of the fact that upstream server extend the URL or not. Please treat following statement as NOT valid as I mentioned in my last post in finding section.

The following log shows error for a query parameter cust=7 which Redis value as simple target URL to proxy_pass to upstream running simple "hello word" . Again it will only work if KEY parameter is hard-coded with the value "cust7".

access_by_lua(nginx.conf:72):16: in function <access_by_lua(nginx.conf:72):1>, client: 10.10.10.3, server: localhost, request: "GET /cust=cust7 HTTP/1.1", host: "10.10.10.3"
2017/10/13 07:37:28 [error] 4612#4612: *33284 lua entry thread aborted: runtime error: access_by_lua(nginx.conf:72):16: bad argument #1 to '__newindex' (string, number, or nil expected, but got userdata)
stack traceback:
coroutine 0:
[C]: in function '__newindex'
access_by_lua(nginx.conf:72):16: in function <access_by_lua(nginx.conf:72):1>, client: 10.10.10.3, server: localhost, request: "GET /cust=cust7 HTTP/1.1", host: "10.10.10.3"

On Friday, 13 October 2017 10:26:59 UTC+1, Muby M wrote:

Hi tokers

Thanks for your reply. Let me explain the scenarios

scenario 1. (not working )

local res, err = red:get(key)

In above statement, the value for key parameter comes from uri part ( 10.10.10.3/?cust=cust2 ) by using built-in variable $arg_cust which gets "cust2" for key parameter . The value retrieved against key "cust2" from the Redis is just target URL for proxy_pass.

scenario 2. (working)

But if the key parameter in the above statement is hardcoded with a value like this

local res,err = red:get("cust2") then it works fine.

Findings

1. Scenario 1 works fine with all other target URL of proxy_pass for cust3 , cust4 and so on ( 10.10.10.3/?cust=cust3 ) . The difference is that in case of cust2, the target URL gets appended with extended new URL path in upstream server (this part "/common/NSLogin.jsp?redirect=/console" gets added ) via embeded _javascript_ in the index page .

2. This means lua code encounters an error when the browser gets extended url as added by target upstream.And this happens ONLY when key
value retrieved dynamically via $arg_cust . local res, err = red:get(key)

Any input will be highly appreciated .

On Friday, 13 October 2017 02:46:07 UTC+1, tokers wrote:
Hi!

There is an assignment that the value is got from redis(res), you should check the type since userdata is not accpeted for ngx.var.VARIABLE.