fix(router) preserve upstream_url path component if exists

When an API's `upstream_url` has a path component, we want the upstream
request to include it as well.

Thanks @javeme for the report.

Fix Kong#2073
Replace Kong#2074 (incomplete)

kong/core/router.lua

@@ -86,6 +86,7 @@ local function marshall_api(api)
     upstream_scheme        = nil,
     upstream_host          = nil,
     upstream_port          = nil,
+    upstream_path           = nil,
   }
 
 
@@ -186,8 +187,9 @@ local function marshall_api(api)
     local parsed = url.parse(api.upstream_url)
 
     api_t.upstream_scheme = parsed.scheme
-    api_t.upstream_host = parsed.host
-    api_t.upstream_port = tonumber(parsed.port)
+    api_t.upstream_host   = parsed.host
+    api_t.upstream_port   = tonumber(parsed.port)
+    api_t.upstream_path    = parsed.path
 
     if not api_t.upstream_port then
       if parsed.scheme == "https" then
@@ -583,6 +585,7 @@ function _M.new(apis)
   function self.exec(ngx)
     local method = ngx.req.get_method()
     local uri = ngx.var.uri
+    local new_uri = uri
     local host_header
     local headers
 
@@ -605,8 +608,22 @@ function _M.new(apis)
 
 
     if api_t.strip_uri_regex then
-      local stripped_uri = re_sub(uri, api_t.strip_uri_regex, "/$1", "jo")
-      ngx.req.set_uri(stripped_uri)
+      local err
+      new_uri, err = re_sub(uri, api_t.strip_uri_regex, "/$1", "jo")
+      if not new_uri then
+        log(ERR, "could not strip URI: ", err)
+        return
+      end
+    end
+
+
+    if api_t.upstream_path then
+      new_uri = api_t.upstream_path .. new_uri
+    end
+
+
+    if new_uri ~= uri then
+      ngx.req.set_uri(new_uri)
     end
 
 
@@ -624,8 +641,8 @@ function _M.new(apis)
     end
 
 
-    return api_t.api, api_t.upstream_scheme, api_t.upstream_host, 
-           api_t.upstream_port, host_header
+    return api_t.api, api_t.upstream_scheme, api_t.upstream_host,
+           api_t.upstream_port, host_header, api_t.upstream_path
   end
 
 

spec/01-unit/12-router_spec.lua

@@ -613,6 +613,23 @@ describe("Router", function()
       assert.equal(443, upstream_port)
     end)
 
+    it("parses path component from upstream_url property", function()
+      local use_case_apis = {
+        {
+          name = "api-1",
+          uris = { "/my-api" },
+          upstream_url = "http://httpbin.org/get",
+        }
+      }
+
+      local router = assert(Router.new(use_case_apis))
+
+      local _ngx = mock_ngx("GET", "/my-api", {})
+      local api, _, _, _, _, upstream_path = router.exec(_ngx)
+      assert.same(use_case_apis[1], api)
+      assert.equal("/get", upstream_path)
+    end)
+
     it("parses upstream_url port", function()
       local use_case_apis = {
         {

spec/02-integration/05-proxy/01-router_spec.lua

@@ -67,6 +67,18 @@ describe("Router", function()
           methods = { "POST", "PUT" },
           uris = { "/post", "/put" },
           strip_uri = false,
+        },
+        {
+          name = "api-3",
+          upstream_url = "http://httpbin.org/status",
+          uris = { "/httpbin" },
+          strip_uri = true,
+        },
+        {
+          name = "api-4",
+          upstream_url = "http://httpbin.org/basic-auth",
+          uris = { "/user" },
+          strip_uri = false,
         }
       }
 
@@ -111,6 +123,30 @@ describe("Router", function()
       assert.response(res).has_status(200)
       assert.equal("api-1", res.headers["kong-api-name"])
     end)
+
+    describe("API with a path component in its upstream_url", function()
+      it("with strip_uri = true", function()
+        local res = assert(client:send {
+          method = "GET",
+          path = "/httpbin/201",
+          headers = { ["kong-debug"] = 1 },
+        })
+
+        assert.res_status(201, res)
+        assert.equal("api-3", res.headers["kong-api-name"])
+      end)
+    end)
+
+    it("with strip_uri = false", function()
+        local res = assert(client:send {
+          method = "GET",
+          path = "/user/passwd",
+          headers = { ["kong-debug"] = 1 },
+        })
+
+        assert.res_status(401, res)
+        assert.equal("api-4", res.headers["kong-api-name"])
+    end)
   end)
 
   describe("invalidation", function()