feat(balancer) recreate request to update Host header

lualib/resty/kong/balancer.lua

@@ -0,0 +1,39 @@
+local _M = {}
+
+
+local ffi = require("ffi")
+local get_request = require("resty.core.base").get_request
+
+
+if ngx.config.subsystem == "http" then
+    ffi.cdef([[
+    int ngx_http_lua_kong_ffi_recreate_request(ngx_http_request_t *r);
+    ]])
+end
+
+
+local get_phase = ngx.get_phase
+local C = ffi.C
+
+
+function _M.update_proxy_request()
+    if ngx.config.subsystem == "http" then
+        if get_phase() ~= "balancer" then
+            error("API disabled in the current context", 2)
+        end
+
+        local r = get_request()
+
+        local ret = C.ngx_http_lua_kong_ffi_recreate_request(r)
+        if ret == ngx.OK then
+            return true
+        end
+
+        error("could not recreate request", 2)
+    end
+
+    return true
+end
+
+
+return _M

src/ngx_http_lua_kong_module.c

@@ -624,3 +624,13 @@ ngx_http_lua_kong_get_upstream_ssl_verify(ngx_http_request_t *r,
 }
 
 #endif
+
+
+extern ngx_int_t ngx_http_proxy_create_request(ngx_http_request_t *r);
+
+
+ngx_int_t
+ngx_http_lua_kong_ffi_recreate_request(ngx_http_request_t *r)
+{
+    return ngx_http_proxy_create_request(r);
+}

t/003-balancer.t

@@ -0,0 +1,83 @@
+# vim:set ft= ts=4 sw=4 et:
+
+use Test::Nginx::Socket::Lua;
+use Cwd qw(cwd);
+
+repeat_each(3);
+
+plan tests => repeat_each() * (blocks() * 2);
+
+my $pwd = cwd();
+
+$ENV{TEST_NGINX_HTML_DIR} ||= html_dir();
+
+no_long_string();
+#no_diff();
+
+run_tests();
+
+__DATA__
+
+=== TEST 1: overwrite Host header on retry
+--- http_config
+    lua_package_path "../lua-resty-core/lib/?.lua;lualib/?.lua;;";
+
+    server {
+        listen 20666;
+        server_name "pittsburgh.test" default_server;
+        return 500;
+    }
+
+    server {
+        listen 20666;
+        server_name "punxsutawney.test";
+        location / {
+            echo "OK, campers, rise and shine";
+        }
+    }
+
+    proxy_next_upstream_tries 10;
+    proxy_next_upstream error http_500;
+    upstream backend {
+        server 0.0.0.1;
+        balancer_by_lua_block {
+            local b = require "ngx.balancer"
+
+            if not ngx.ctx.tries then
+                ngx.ctx.tries = 0
+            end
+
+            if ngx.ctx.tries > 0 then
+                local kb = require("resty.kong.balancer")
+                ngx.var.upstream_host = "punxsutawney.test"
+                kb.update_proxy_request()
+            end
+
+            ngx.ctx.tries = ngx.ctx.tries + 1
+            b.set_more_tries(1)
+            assert(b.set_current_peer("127.0.0.1", 20666))
+        }
+    }
+
+
+--- config
+
+    location /t {
+        proxy_pass http://backend/;
+        set $upstream_host '';
+        proxy_set_header Host $upstream_host;
+        access_by_lua_block {
+            ngx.var.upstream_host = "strike"
+        }
+    }
+
+--- request
+GET /t
+
+--- more_headers
+Host: thereandback.test
+
+--- response_body_like
+OK, campers, rise and shine
+
+--- error_code: 200