Add function to call /api/v4/geo/proxy

When this instance is a Geo proxy, just log that fact for now.

workhorse/internal/api/api.go

@@ -3,6 +3,7 @@ package api
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -29,6 +30,8 @@ const (
 	ResponseContentType = "application/vnd.gitlab-workhorse+json"
 
 	failureResponseLimit = 32768
+
+	geoProxyEndpointPath = "/api/v4/geo/proxy"
 )
 
 type API struct {
@@ -37,6 +40,8 @@ type API struct {
 	Version string
 }
 
+var ErrNotGeoSecondary = errors.New("this is not a Geo secondary site")
+
 var (
 	requestsCounter = promauto.NewCounterVec(
 		prometheus.CounterOpts{
@@ -61,6 +66,10 @@ func NewAPI(myURL *url.URL, version string, roundTripper http.RoundTripper) *API
 	}
 }
 
+type GeoProxyEndpointResponse struct {
+	GeoProxyURL string `json:"geo_proxy_url"`
+}
+
 type HandleFunc func(http.ResponseWriter, *http.Request, *Response)
 
 type MultipartUploadParams struct {
@@ -389,3 +398,40 @@ func bufferResponse(r io.Reader) (*bytes.Buffer, error) {
 func validResponseContentType(resp *http.Response) bool {
 	return helper.IsContentType(ResponseContentType, resp.Header.Get("Content-Type"))
 }
+
+// TODO: Cache the result of the API requests https://gitlab.com/gitlab-org/gitlab/-/issues/329671
+func (api *API) GetGeoProxyURL() (*url.URL, error) {
+	geoProxyApiUrl := *api.URL
+	geoProxyApiUrl.Path, geoProxyApiUrl.RawPath = joinURLPath(api.URL, geoProxyEndpointPath)
+	geoProxyApiReq := &http.Request{
+		Method: "GET",
+		URL:    &geoProxyApiUrl,
+		Header: make(http.Header),
+	}
+
+	httpResponse, err := api.doRequestWithoutRedirects(geoProxyApiReq)
+	if err != nil {
+		return nil, fmt.Errorf("GetGeoProxyURL: do request: %v", err)
+	}
+	defer httpResponse.Body.Close()
+
+	if httpResponse.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("GetGeoProxyURL: Received HTTP status code: %v", httpResponse.StatusCode)
+	}
+
+	response := &GeoProxyEndpointResponse{}
+	if err := json.NewDecoder(httpResponse.Body).Decode(response); err != nil {
+		return nil, fmt.Errorf("GetGeoProxyURL: decode response: %v", err)
+	}
+
+	if response.GeoProxyURL == "" {
+		return nil, ErrNotGeoSecondary
+	}
+
+	geoProxyURL, err := url.Parse(response.GeoProxyURL)
+	if err != nil {
+		return nil, fmt.Errorf("GetGeoProxyURL: Could not parse Geo proxy URL: %v, err: %v", response.GeoProxyURL, err)
+	}
+
+	return geoProxyURL, nil
+}

workhorse/internal/api/api_test.go

+package api
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"regexp"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"gitlab.com/gitlab-org/labkit/log"
+
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/helper"
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/secret"
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/testhelper"
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/upstream/roundtripper"
+)
+
+func TestGetGeoProxyURLWhenGeoSecondary(t *testing.T) {
+	geoProxyURL, err := getGeoProxyURLGivenResponse(t, `{"geo_proxy_url":"http://primary"}`)
+
+	require.NoError(t, err)
+	require.NotNil(t, geoProxyURL)
+	require.Equal(t, "http://primary", geoProxyURL.String())
+}
+
+func TestGetGeoProxyURLWhenGeoPrimaryOrNonGeo(t *testing.T) {
+	geoProxyURL, err := getGeoProxyURLGivenResponse(t, "{}")
+
+	require.Error(t, err)
+	require.Equal(t, ErrNotGeoSecondary, err)
+	require.Nil(t, geoProxyURL)
+}
+
+func getGeoProxyURLGivenResponse(t *testing.T, givenInternalApiResponse string) (*url.URL, error) {
+	t.Helper()
+	ts := testRailsServer(regexp.MustCompile(`/api/v4/geo/proxy`), 200, givenInternalApiResponse)
+	defer ts.Close()
+	backend := helper.URLMustParse(ts.URL)
+	version := "123"
+	rt := roundtripper.NewTestBackendRoundTripper(backend)
+	testhelper.ConfigureSecret()
+
+	apiClient := NewAPI(backend, version, rt)
+
+	geoProxyURL, err := apiClient.GetGeoProxyURL()
+
+	return geoProxyURL, err
+}
+
+func testRailsServer(url *regexp.Regexp, code int, body string) *httptest.Server {
+	return testhelper.TestServerWithHandler(url, func(w http.ResponseWriter, r *http.Request) {
+		// return a 204 No Content response if we don't receive the JWT header
+		if r.Header.Get(secret.RequestHeader) == "" {
+			w.WriteHeader(204)
+			return
+		}
+
+		w.Header().Set("Content-Type", ResponseContentType)
+
+		logEntry := log.WithFields(log.Fields{
+			"method": r.Method,
+			"url":    r.URL,
+		})
+		logEntryWithCode := logEntry.WithField("code", code)
+
+		// Write pure string
+		logEntryWithCode.Info("UPSTREAM")
+
+		w.WriteHeader(code)
+		fmt.Fprint(w, body)
+	})
+}

workhorse/internal/upstream/routes.go

@@ -191,12 +191,7 @@ func buildProxy(backend *url.URL, version string, rt http.RoundTripper, cfg conf
 // see upstream.ServeHTTP
 
 func configureRoutes(u *upstream) {
-	api := apipkg.NewAPI(
-		u.Backend,
-		u.Version,
-		u.RoundTripper,
-	)
-
+	api := u.APIClient
 	static := &staticpages.Static{DocumentRoot: u.DocumentRoot, Exclude: staticExclude}
 	proxy := buildProxy(u.Backend, u.Version, u.RoundTripper, u.Config)
 	cableProxy := proxypkg.NewProxy(u.CableBackend, u.Version, u.CableRoundTripper)

workhorse/internal/upstream/upstream.go

@@ -8,6 +8,7 @@ package upstream
 
 import (
 	"fmt"
+	"os"
 
 	"net/http"
 	"strings"
@@ -15,8 +16,10 @@ import (
 	"github.com/sirupsen/logrus"
 	"gitlab.com/gitlab-org/labkit/correlation"
 
+	apipkg "gitlab.com/gitlab-org/gitlab-workhorse/internal/api"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/config"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/helper"
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/log"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/rejectmethods"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/upload"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/upstream/roundtripper"
@@ -32,11 +35,13 @@ var (
 
 type upstream struct {
 	config.Config
-	URLPrefix         urlprefix.Prefix
-	Routes            []routeEntry
-	RoundTripper      http.RoundTripper
-	CableRoundTripper http.RoundTripper
-	accessLogger      *logrus.Logger
+	URLPrefix             urlprefix.Prefix
+	Routes                []routeEntry
+	RoundTripper          http.RoundTripper
+	CableRoundTripper     http.RoundTripper
+	APIClient             *apipkg.API
+	accessLogger          *logrus.Logger
+	enableGeoProxyFeature bool
 }
 
 func NewUpstream(cfg config.Config, accessLogger *logrus.Logger) http.Handler {
@@ -60,6 +65,13 @@ func newUpstream(cfg config.Config, accessLogger *logrus.Logger, routesCallback
 	up.RoundTripper = roundtripper.NewBackendRoundTripper(up.Backend, up.Socket, up.ProxyHeadersTimeout, cfg.DevelopmentMode)
 	up.CableRoundTripper = roundtripper.NewBackendRoundTripper(up.CableBackend, up.CableSocket, up.ProxyHeadersTimeout, cfg.DevelopmentMode)
 	up.configureURLPrefix()
+	up.APIClient = apipkg.NewAPI(
+		up.Backend,
+		up.Version,
+		up.RoundTripper,
+	)
+	// Kind of a feature flag. See https://gitlab.com/groups/gitlab-org/-/epics/5914#note_564974130
+	up.enableGeoProxyFeature = os.Getenv("GEO_SECONDARY_PROXY") == "1"
 	routesCallback(&up)
 
 	var correlationOpts []correlation.InboundHandlerOption
@@ -108,6 +120,17 @@ func (u *upstream) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	// Look for a matching route
 	var route *routeEntry
+
+	if u.enableGeoProxyFeature {
+		geoProxyURL, err := u.APIClient.GetGeoProxyURL()
+
+		if err == nil {
+			log.WithRequest(r).WithFields(log.Fields{"geoProxyURL": geoProxyURL}).Info("Geo Proxy: Set route according to Geo Proxy logic")
+		} else if err != apipkg.ErrNotGeoSecondary {
+			log.WithRequest(r).WithError(err).Error("Geo Proxy: Unable to determine Geo Proxy URL. Falling back to normal routing")
+		}
+	}
+
 	for _, ro := range u.Routes {
 		if ro.isMatch(prefix.Strip(URIPath), r) {
 			route = &ro