readyz handler (#50)

See also flashbots/rbuilder#643

Author: metachris

proxy/receiver_api.go

@@ -5,6 +5,7 @@ import (
 	_ "embed"
 	"errors"
 	"log/slog"
+	"net/http"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -70,12 +71,34 @@ func (prx *ReceiverProxy) UserJSONRPCHandler(maxRequestBodySizeBytes int64) (*rp
 			Log:                              prx.Log,
 			MaxRequestBodySizeBytes:          maxRequestBodySizeBytes,
 			VerifyRequestSignatureFromHeader: true,
+			ReadyHandler:                     prx.readyHandler,
 		},
 	)
 
 	return handler, err
 }
 
+// readyHandler calls /readyz on rbuilder
+func (prx *ReceiverProxy) readyHandler(w http.ResponseWriter, r *http.Request) error {
+	resp, err := http.Get(prx.localBuilderEndpoint + "/readyz")
+	if err != nil {
+		prx.Log.Warn("Failed to check builder readiness", slog.Any("error", err))
+		http.Error(w, "not ready", http.StatusServiceUnavailable)
+		return nil
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		http.Error(w, "not ready", http.StatusServiceUnavailable)
+		return nil
+	}
+
+	// If the builder is ready, return 200 OK
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write([]byte("ready"))
+	return nil
+}
+
 func (prx *ReceiverProxy) ValidateSigner(ctx context.Context, req *ParsedRequest, systemEndpoint bool) error {
 	req.signer = rpcserver.GetSigner(ctx)
 	if !systemEndpoint {

proxy/receiver_proxy.go

@@ -39,7 +39,8 @@ type ReceiverProxy struct {
 
 	OrderflowSigner *signature.Signer
 
-	localBuilder rpcclient.RPCClient
+	localBuilder         rpcclient.RPCClient
+	localBuilderEndpoint string
 
 	UserHandler   http.Handler
 	SystemHandler http.Handler
@@ -109,6 +110,7 @@ func NewReceiverProxy(config ReceiverProxyConfig) (*ReceiverProxy, error) {
 		ConfigHub:                   NewBuilderConfigHub(config.Log, config.BuilderConfigHubEndpoint),
 		OrderflowSigner:             orderflowSigner,
 		localBuilder:                localBuilder,
+		localBuilderEndpoint:        config.LocalBuilderEndpoint,
 		requestUniqueKeysRLU:        expirable.NewLRU[uuid.UUID, struct{}](requestsRLUSize, nil, requestsRLUTTL),
 		replacementNonceRLU:         expirable.NewLRU[replacementNonceKey, int](replacementNonceSize, nil, replacementNonceTTL),
 		userAPIRateLimiter:          userAPIRateLimiter,

proxy/receiver_proxy_test.go

@@ -671,3 +671,20 @@ func TestValidateLocalBundles(t *testing.T) {
 
 	proxiesFlushQueue()
 }
+
+func TestJSONRPCServerReadyzOK(t *testing.T) {
+	tempDir := t.TempDir()
+	certPath := path.Join(tempDir, "cert")
+	keyPath := path.Join(tempDir, "key")
+	proxy, err := StartTestOrderflowProxy("1", certPath, keyPath)
+	require.NoError(t, err)
+
+	req := httptest.NewRequest(http.MethodGet, "/readyz", nil)
+
+	rr := httptest.NewRecorder()
+	proxy.localServer.Handler.ServeHTTP(rr, req)
+	respBody, err := io.ReadAll(rr.Body)
+	require.NoError(t, err)
+	require.Equal(t, http.StatusOK, rr.Code)
+	require.Contains(t, string(respBody), "ready")
+}