nginx return 200 if rewrite_by_lua_block response header contains pattern

Question

I need nginx to return 200 code on some location only if rewrite_by_lua_block response contains custom header with pattern (for google compute engine balancer healthcheck).

I'm very newbie in lua, so any help's greatly appreciated.

Answer 1

I suggest to try (untested)

header_filter_by_lua_block {
   if ngx.status == 200 then
      local from, to, err = ngx.re.find( ngx.header.Foo, "your_regexp_here")
      if not from then
         ngx.status = 500 -- use the error code you need
      end
   end
}

Keep in mind - your should place header_filter_by_lua_block directive into location where your request is really sent to upstream, say where you redirect to by rewrite_by_lua_block.