CODEWITHSUNDEEP
nginxluanginx-reverse-proxynginx-locationopenresty
Vinay Mundada
Vinay Mundada

Reputation: 327

Nginx access_by_lua_block not executed in case of 3XX redirects

I am using the access_by_lua_block in my nginx configuration to add/modify custom request headers (let's say ngx.req.set_header("foo", "bar")). I am accessing these headers within the header_filter_by_lua_block as ngx.var["http_foo"] just before returning any response to the client. This works fine in case of passing the request to upstream, however it doesn't work in case of redirects. So basically,

This works (No redirect).

location /abc {
   proxy_pass some_upstream;

   access_by_lua_block {
      ngx.req.set_header("foo", "bar")
   }

   header_filter_by_lua_block {
     ngx.header["foo2"] = ngx.var["http_foo"] # this is correctly getting the value of "foo" header set above
   }
}

This doesn't work (With Redirect)

location /abc {
   access_by_lua_block {
      ngx.req.set_header("foo", "bar")
   }

   header_filter_by_lua_block {
     ngx.header["foo2"] = ngx.var["http_foo"] # this is not getting the value of "foo" header set above
   }

   return 301 xyz.com;
}

The access_by_lua_block is not getting executed in case of redirects only (return 301 statement). I don't understand why so? Because access_by_lua_block has a execution priority before the content phase (link)

Upvotes: 4

Views: 8034

Answers (1)

Ivan Shatsky
Ivan Shatsky

Reputation: 15518

As far as I understand, execution of return directive happens within the rewrite phase, and access phase doesn't executed at all in this case. You can try to change access_by_lua_block to rewrite_by_lua_block and see what happens.

Update

First attempt to solve the problem gives nothing. Indeed, as lua-ngx-module documentation for rewrite_by_lua states:

Note that this handler always runs after the standard ngx_http_rewrite_module.

What else you could try is to do the redirect inside the rewrite_by_lua_block:

location /abc {
   rewrite_by_lua_block {
      ngx.req.set_header("foo", "bar")
      ngx.redirect("xyz.com", 301)
   }

   header_filter_by_lua_block {
     ngx.header["foo2"] = ngx.var["http_foo"] # this is not getting the value of "foo" header set above
   }
}

Upvotes: 3

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