Facing issues with ngx.upstream.get_upstreams()

bclodius · 2016-01-23T04:32:51+00:00

Yichun Zhang (agentzh) sent: Friday, January 22, 2016 12:29 AM > > I am happy to announce the new formal release, 1.9.7.2, of the > OpenResty web p...

Facing issues with ngx.upstream.get_upstreams()

bclodius

Hello All!

Here's my use case: I'm creating a lightweight api gateway, in the logging I want to include the upstream server that a request was forwarded to.

I can replicate the sample provided in the readme just fine: https://github.com/openresty/lua-upstream-nginx-module

But whilst trying to use ngx.upstream.get_upstreams() inside any of my previously working lua modules I am continuously getting "Segmentation fault".

nginx: [error] [lua] router.lua:183: init_upstream_servers_two(): HELLO
nginx: [error] [lua] router.lua:185: init_upstream_servers_two(): HELLO
nginx: [error] [lua] router.lua:187: init_upstream_servers_two(): HELLO
Segmentation fault

  local upstream = require "ngx.upstream"

  ngx_log(ngx_ERR, "HELLO") 

  local get_servers = upstream.get_servers 

  ngx_log(ngx_ERR, "HELLO") 

  local get_upstreams = upstream.get_upstreams 

  ngx_log(ngx_ERR, "HELLO") 

  --fails on this line
  local us = get_upstreams() 

  ngx_log(ngx_ERR, "HELLO")

Is ngx.upstream only supported on certain directives/flows?

Thanks in advance!

bclodius

Thanks to the help of a colleague we figured out the issue. Seems that nginx does not load upstreams until request phase. Since I was trying to load the details in init_lua it was throwing a segmentation fault.

I refactored the flow to load the properties globally on very first request to server.

agentzh

Hello!

On Mon, Jan 25, 2016 at 1:48 PM, bclod wrote:
> Thanks to the help of a colleague we figured out the issue.  Seems that
> nginx does not load upstreams until request phase.  Since I was trying to
> load the details in init_lua it was throwing a segmentation fault.
>
> I refactored the flow to load the properties globally on very first request
> to server.
>

I think we should explicitly check for the init_by_lua* context to
avoid segmentation faults. A friendly message is more helpful. Will
you please contribute a patch for this? Thanks a lot! And I'm glad you
figured it out.

Best regards,
-agentzh

agentzh

Hello!

On Mon, Jan 25, 2016 at 1:48 PM, bclod wrote:
> Thanks to the help of a colleague we figured out the issue.  Seems that
> nginx does not load upstreams until request phase.  Since I was trying to
> load the details in init_lua it was throwing a segmentation fault.
>
> I refactored the flow to load the properties globally on very first request
> to server.
>

BTW, not just request phase works, the init_worker_by_lua* and timer
handler contexts should work as well.

Best regards,
-agentzh