ngx.exit not terminating request

maanas · 2012-12-09T22:04:21+00:00

Hello, folks! I am happy to announce the new development version of ngx_openresty, 1.2.4.11: http://openresty.org/#Download Special thanks go to all o...

ngx.exit not terminating request

maanas

I m trying to evaluate an _expression_ is lua which is evaluated correctly. There after on condition i m calling ngx.exit(ngx.HTTP_OK). I have read about status code >= 200 should be able to abort the execution of request and status code < 200 aborting the phase_handler.

My sample location config is

location ~ /test/location/[^/]* {

default_type 'text/plain';

set $uid $1;

# Check for numeric uid

content_by_lua '

if tonumber(ngx.var.uid) == nil then

ngx.status = ngx.HTTP_GONE

ngx.say([[{"status":"ERROR", "message":"Invalid uid"}]])

ngx.exit(ngx.HTTP_OK)

end;

# This is only GET Endpoint

if ($request_method = GET) {

# Retrive all the projects for this UID

set $sql 'SELECT * FROM users WHERE uid = $uid ';

drizzle_query $sql;

drizzle_pass do;

rds_json on;

drizzle_connect_timeout 500ms; # default 60s

drizzle_send_query_timeout 2s; # default 60s

drizzle_recv_cols_timeout 1s; # default 60s

drizzle_recv_rows_timeout 1s; # default 60s

}

If i give a numeric uid it works if i give non numeric uid the lua evaluates correctly but the execution does not stop and i get sql error in drizzle.

Any suggestions.

I would also like to know how i can enable connection pool in lua_mysql module.

Thanks

agentzh

Hello!

On Sun, Dec 9, 2012 at 6:04 AM, Maanas wrote:
> I m trying to evaluate an expression is lua which is evaluated correctly.
> There after on condition i m calling ngx.exit(ngx.HTTP_OK). I have read
> about status code >= 200 should be able to abort the execution of request
> and status code < 200 aborting the phase_handler.
>
> My sample location config is
> location ~ /test/location/[^/]* {

I think you forgot parentheses in the location regex here? Otherwise
the $1 variable you used below will always be nil.

[...]
> }
>
> If i give a numeric uid it works if i give non numeric uid the lua evaluates
> correctly but the execution does not stop and i get sql error in drizzle.
>

You're using the Nginx "if" directive in the wrong way. In both cases
(numeric and nonnumeric uid), your content_by_lua directive was never
evaluated at all.

The evaluation order of the directives in your nginx.conf is like this:

    set $uid $1;
    if ($request_method = GET)
    set $sql 'SELECT * FROM users WHERE uid = $uid ';
    drizzle_pass do;

That is, the "if" directive always runs at the Nginx "rewrite" request
processing phase, way before the "content" phase that the
content_by_lua and drizzle_pass directives run in, even if you write
content_by_lua before "if".

Also, the "if" directive creates an anonymous nested location within
your location ~ /test/location/[^/]*, and once your "if" condition is
evaluated to true, only the content handler (in this case,
drizzle_pass) defined in that anonymous location will be evaluated.

You're getting the SQL error when $1 does not look like a number just
because your $uid is not quoted to be a valid SQL string literal. If
you enable the debug logging in your Nginx, you can see the following
message in your error.log:

    [debug] 20521#0: *1 drizzle sending query "SELECT * FROM users
WHERE uid = foo"

It cannot be a valid SQL. You should use the set_quote_sql_str
directive or the ngx.quote_sql_str() Lua function to always quote your
SQL literals properly (it is also good to guard against SQL injection
attacks).

The suggestion is to avoid using nginx's "if" and sticking with Lua
wherever possible however. Here is an example that should do what you
want (already tested on my side):

    location ~ ^/test/location/([^/]*) {
        default_type 'text/plain';

        # Check for numeric uid and generate the SQL query in $sql
        set $sql '';
        access_by_lua '
            if ngx.req.get_method() ~= "GET" then
                return ngx.exit(400)
            end

            local uid = ngx.var[1]
            if not tonumber(uid) then
                ngx.status = ngx.HTTP_GONE
                ngx.say([[{"status":"ERROR", "message":"Invalid uid"}]])
                return ngx.exit(ngx.HTTP_OK)
            end;

            local quoted_uid = ngx.quote_sql_str(uid)
            ngx.var.sql = "SELECT * FROM users WHERE uid = " .. quoted_uid
        ';

        drizzle_query $sql;
        drizzle_pass do;
        rds_json on;
        drizzle_connect_timeout    500ms; # default 60s
        drizzle_send_query_timeout 2s;    # default 60s
        drizzle_recv_cols_timeout  1s;    # default 60s
        drizzle_recv_rows_timeout  1s;    # default 60s
    }

Let's test it a bit with curl:

    $ curl -i localhost:8080/test/location/1
    HTTP/1.1 200 OK
    Server: nginx/1.2.4
    Date: Sun, 09 Dec 2012 18:33:21 GMT
    Content-Type: application/json
    Transfer-Encoding: chunked
    Connection: keep-alive
    X-Resty-DBD-Module: ngx_drizzle 0.0.15

    [{"uid":1,"name":"Tom"}]

    $ curl -i localhost:8080/test/location/foo
    HTTP/1.1 410 Gone
    Server: nginx/1.2.4
    Date: Sun, 09 Dec 2012 18:34:29 GMT
    Content-Type: text/plain
    Transfer-Encoding: chunked
    Connection: keep-alive

    {"status":"ERROR", "message":"Invalid uid"}

See the following tutorials on more details about the execution order
of Nginx module directives:

    http://agentzh.org/misc/nginx/agentzh-nginx-tutorials-enuk.html

And also the following article on nginx "if":

    http://agentzh.blogspot.com/2011/03/how-nginx-location-if-works.html

> I would also like to know how i can enable connection pool in lua_mysql module.

Do you mean the lua-resty-mysql library? You can enable the MySQL
connection pool by calling the set_keepalive method:

    https://github.com/agentzh/lua-resty-mysql#set_keepalive

Best regards,
-agentzh

maanas

Thanks a ton agentzh!!!

On Mon, Dec 10, 2012 at 12:07 AM, agentzh <age...@gmail.com> wrote:

Hello!

On Sun, Dec 9, 2012 at 6:04 AM, Maanas wrote:
> I m trying to evaluate an _expression_ is lua which is evaluated correctly.
> There after on condition i m calling ngx.exit(ngx.HTTP_OK). I have read
> about status code >= 200 should be able to abort the execution of request
> and status code < 200 aborting the phase_handler.
>
> My sample location config is
> location ~ /test/location/[^/]* {

I think you forgot parentheses in the location regex here? Otherwise
the $1 variable you used below will always be nil.

[...]
> }
>
> If i give a numeric uid it works if i give non numeric uid the lua evaluates
> correctly but the execution does not stop and i get sql error in drizzle.
>

You're using the Nginx "if" directive in the wrong way. In both cases
(numeric and nonnumeric uid), your content_by_lua directive was never
evaluated at all.

The evaluation order of the directives in your nginx.conf is like this:

set $uid $1;
if ($request_method = GET)
set $sql 'SELECT * FROM users WHERE uid = $uid ';
drizzle_pass do;

That is, the "if" directive always runs at the Nginx "rewrite" request
processing phase, way before the "content" phase that the
content_by_lua and drizzle_pass directives run in, even if you write
content_by_lua before "if".

Also, the "if" directive creates an anonymous nested location within
your location ~ /test/location/[^/]*, and once your "if" condition is
evaluated to true, only the content handler (in this case,
drizzle_pass) defined in that anonymous location will be evaluated.

You're getting the SQL error when $1 does not look like a number just
because your $uid is not quoted to be a valid SQL string literal. If
you enable the debug logging in your Nginx, you can see the following
message in your error.log:

[debug] 20521#0: *1 drizzle sending query "SELECT * FROM users
WHERE uid = foo"

It cannot be a valid SQL. You should use the set_quote_sql_str
directive or the ngx.quote_sql_str() Lua function to always quote your
SQL literals properly (it is also good to guard against SQL injection
attacks).

The suggestion is to avoid using nginx's "if" and sticking with Lua
wherever possible however. Here is an example that should do what you
want (already tested on my side):

location ~ ^/test/location/([^/]*) {
default_type 'text/plain';

# Check for numeric uid and generate the SQL query in $sql
set $sql '';
access_by_lua '
if ngx.req.get_method() ~= "GET" then
return ngx.exit(400)
end

local uid = ngx.var[1]
if not tonumber(uid) then
ngx.status = ngx.HTTP_GONE
ngx.say([[{"status":"ERROR", "message":"Invalid uid"}]])
return ngx.exit(ngx.HTTP_OK)
end;

local quoted_uid = ngx.quote_sql_str(uid)
ngx.var.sql = "SELECT * FROM users WHERE uid = " .. quoted_uid
';

drizzle_query $sql;
drizzle_pass do;
rds_json on;
drizzle_connect_timeout 500ms; # default 60s
drizzle_send_query_timeout 2s; # default 60s
drizzle_recv_cols_timeout 1s; # default 60s
drizzle_recv_rows_timeout 1s; # default 60s
}

Let's test it a bit with curl:

$ curl -i localhost:8080/test/location/1
HTTP/1.1 200 OK
Server: nginx/1.2.4
Date: Sun, 09 Dec 2012 18:33:21 GMT
Content-Type: application/json
Transfer-Encoding: chunked
Connection: keep-alive
X-Resty-DBD-Module: ngx_drizzle 0.0.15

[{"uid":1,"name":"Tom"}]

$ curl -i localhost:8080/test/location/foo
HTTP/1.1 410 Gone
Server: nginx/1.2.4
Date: Sun, 09 Dec 2012 18:34:29 GMT
Content-Type: text/plain
Transfer-Encoding: chunked
Connection: keep-alive

{"status":"ERROR", "message":"Invalid uid"}

See the following tutorials on more details about the execution order
of Nginx module directives:

http://agentzh.org/misc/nginx/agentzh-nginx-tutorials-enuk.html

And also the following article on nginx "if":

http://agentzh.blogspot.com/2011/03/how-nginx-location-if-works.html

> I would also like to know how i can enable connection pool in lua_mysql module.

Do you mean the lua-resty-mysql library? You can enable the MySQL
connection pool by calling the set_keepalive method:

https://github.com/agentzh/lua-resty-mysql#set_keepalive

Best regards,
-agentzh
.