GODT-1917: gRPC service should use random port.

WIP: bridge-gui wait and parse gRPC service config fie.

internal/app/bridge/bridge.go

@@ -160,6 +160,7 @@ func main(b *base.Base, c *cli.Context) error { //nolint:funlen
 		b.Updater,
 		bridge,
 		b,
+		b.Locations,
 	)
 
 	// Watch for updates routine

internal/frontend/bridge-gui/bridge-gui/QMLBackend.cpp

@@ -37,9 +37,9 @@ QMLBackend::QMLBackend()
 
 
 //****************************************************************************************************************************************************
-//
+/// \param[in] serviceConfig
 //****************************************************************************************************************************************************
-void QMLBackend::init()
+void QMLBackend::init(GRPCConfig const &serviceConfig)
 {
     users_ = new UserList(this);
 
@@ -47,7 +47,7 @@ void QMLBackend::init()
     this->connectGrpcEvents();
 
     QString error;
-    if (app().grpc().connectToServer(error))
+    if (app().grpc().connectToServer(serviceConfig, error))
         app().log().info("Connected to backend via gRPC service.");
     else
         throw Exception(QString("Cannot connectToServer to go backend via gRPC: %1").arg(error));

internal/frontend/bridge-gui/bridge-gui/QMLBackend.h

@@ -42,7 +42,7 @@ public: // member functions.
     ~QMLBackend() override = default; ///< Destructor.
     QMLBackend &operator=(QMLBackend const &) = delete; ///< Disabled assignment operator.
     QMLBackend &operator=(QMLBackend &&) = delete; ///< Disabled move assignment operator.
-    void init(); ///< Initialize the backend.
+    void init(GRPCConfig const &serviceConfig); ///< Initialize the backend.
     bool waitForEventStreamReaderToFinish(qint32 timeoutMs); ///< Wait for the event stream reader to finish.
 
     // invokable methods can be called from QML. They generally return a value, which slots cannot do.

internal/frontend/bridge-gui/bridge-gui/main.cpp

@@ -41,6 +41,7 @@ namespace
 
     QString const bridgeLock = "bridge-gui.lock"; ///< file name used for the lock file.
     QString const exeName = "bridge" + exeSuffix; ///< The bridge executable file name.*
+    qint64 const grpcServiceConfigWaitDelayMs = 60000; ///< The wait delay for the gRPC config file in milliseconds.
 }
 
 
@@ -261,9 +262,16 @@ int main(int argc, char *argv[])
         log.setLevel(logLevel);
 
         if (!attach)
+        {
+            // before launching bridge, we remove any trailing service config file, because we need to make sure we get a newly generated one.
+            GRPCClient::removeServiceConfigFile();
             launchBridge(args);
+        }
 
-        app().backend().init();
+        app().backend().init(GRPCClient::waitAndRetrieveServiceConfig(attach ? 0 : grpcServiceConfigWaitDelayMs));
+
+        if (!attach)
+            GRPCClient::removeServiceConfigFile();
 
         QQmlApplicationEngine engine;
         std::unique_ptr<QQmlComponent> rootComponent(createRootQmlComponent(engine));

internal/frontend/bridge-gui/bridgepp/CMakeLists.txt

@@ -107,13 +107,13 @@ add_library(bridgepp
     bridgepp/Exception/Exception.h bridgepp/Exception/Exception.cpp
     bridgepp/GRPC/GRPCClient.cpp bridgepp/GRPC/GRPCClient.h
     bridgepp/GRPC/EventFactory.cpp bridgepp/GRPC/EventFactory.h
+    bridgepp/GRPC/GRPCConfig.cpp bridgepp/GRPC/GRPCConfig.h
     bridgepp/GRPC/GRPCUtils.cpp bridgepp/GRPC/GRPCUtils.h
     ${PROTO_CPP_FILE} ${PROTO_H_FILE} ${GRPC_CPP_FILE} ${GRPC_H_FILE}
     bridgepp/Log/Log.h bridgepp/Log/Log.cpp
     bridgepp/ProcessMonitor.cpp bridgepp/ProcessMonitor.h
     bridgepp/User/User.cpp bridgepp/User/User.h
-    bridgepp/Worker/Worker.h bridgepp/Worker/Overseer.h bridgepp/Worker/Overseer.cpp
+    bridgepp/Worker/Worker.h bridgepp/Worker/Overseer.h bridgepp/Worker/Overseer.cpp)
-    )
 
 target_include_directories(bridgepp PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 

internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCClient.cpp

@@ -43,6 +43,54 @@ int const maxCertificateWaitMsecs = 60 * 1000; ///< Amount of time we wait for h
 }
 
 
+//****************************************************************************************************************************************************
+//
+//****************************************************************************************************************************************************
+void GRPCClient::removeServiceConfigFile()
+{
+    QString const path = serviceConfigPath();
+    if (!QFile(path).exists())
+        return;
+    if (!QFile().remove(path))
+        throw Exception("Could not remove gRPC service config file.");
+}
+
+
+//****************************************************************************************************************************************************
+/// \param[in] timeoutMs The timeout in milliseconds
+/// \return The service config.
+//****************************************************************************************************************************************************
+GRPCConfig GRPCClient::waitAndRetrieveServiceConfig(qint64 timeoutMs)
+{
+    QString const path = serviceConfigPath();
+    QFile file(path);
+
+    QElapsedTimer timer;
+    timer.start();
+    bool found = false;
+    while (true)
+    {
+        if (file.exists())
+        {
+            found = true;
+            break;
+        }
+        if (timer.elapsed() > timeoutMs)
+            break;
+        QThread::msleep(100);
+    }
+
+    if (!found)
+        throw Exception("Server did not provide gRPC service configuration in time.");
+
+    GRPCConfig sc;
+    if (!sc.load(path))
+        throw Exception("The gRPC service configuration file is invalid.");
+
+    return sc;
+}
+
+
 //****************************************************************************************************************************************************
 /// \brief wait for certificate generation by Bridge
 /// \return server certificate generated by Bridge
@@ -110,14 +158,15 @@ void GRPCClient::setLog(Log *log)
 /// \param[out] outError If the function returns false, this variable contains a description of the error.
 /// \return true iff the connection was successful.
 //****************************************************************************************************************************************************
-bool GRPCClient::connectToServer(QString &outError)
+bool GRPCClient::connectToServer(GRPCConfig const &config, QString &outError)
 {
     try
     {
         SslCredentialsOptions opts;
         opts.pem_root_certs += this->getServerCertificate();
 
-        channel_ = CreateChannel("127.0.0.1:9292", grpc::SslCredentials(opts));
+        QString const address = QString("127.0.0.1:%1").arg(config.port);
+        channel_ = CreateChannel(address.toStdString(), grpc::SslCredentials(opts));
         if (!channel_)
             throw Exception("Channel creation failed.");
 
@@ -130,7 +179,7 @@ bool GRPCClient::connectToServer(QString &outError)
         while (true)
         {
             if (log_)
-                log_->debug(QString("Connection to gRPC server. attempt #%1").arg(++i));
+                log_->debug(QString("Connection to gRPC server at %1. attempt #%2").arg(address).arg(++i));
 
             if (channel_->WaitForConnected(gpr_time_add(gpr_now(GPR_CLOCK_REALTIME), gpr_time_from_seconds(5, GPR_TIMESPAN))))
                 break; // connection established.

internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCClient.h

@@ -22,6 +22,7 @@
 
 #include "../User/User.h"
 #include "../Log/Log.h"
+#include "GRPCConfig.h"
 #include "bridge.grpc.pb.h"
 #include "grpc++/grpc++.h"
 
@@ -46,6 +47,10 @@ typedef grpc::Status (grpc::Bridge::Stub::*StringParamMethod)(grpc::ClientContex
 class GRPCClient : public QObject
 {
 Q_OBJECT
+public: // static member functions
+    static void removeServiceConfigFile(); ///< Delete the service config file.
+    static GRPCConfig waitAndRetrieveServiceConfig(qint64 timeoutMs); ///< Wait and retrieve the service configuration.
+
 public: // member functions.
     GRPCClient() = default; ///< Default constructor.
     GRPCClient(GRPCClient const &) = delete; ///< Disabled copy-constructor.
@@ -54,7 +59,7 @@ public: // member functions.
     GRPCClient &operator=(GRPCClient const &) = delete; ///< Disabled assignment operator.
     GRPCClient &operator=(GRPCClient &&) = delete; ///< Disabled move assignment operator.
     void setLog(Log *log); ///< Set the log for the client.
-    bool connectToServer(QString &outError); ///< Establish connection to the gRPC server.
+    bool connectToServer(GRPCConfig const &config, QString &outError); ///< Establish connection to the gRPC server.
 
     grpc::Status addLogEntry(Log::Level level, QString const &package, QString const &message); ///< Performs the "AddLogEntry" gRPC call.
     grpc::Status guiReady(); ///< performs the "GuiReady" gRPC call.
@@ -218,6 +223,7 @@ private:
     grpc::Status methodWithStringParam(StringParamMethod method, QString const &str); ///< Perform a gRPC call that takes a string as a parameter and returns an Empty.
     SPUser parseGRPCUser(grpc::User const &grpcUser); ///< Parse a gRPC user struct and return a User.
 
+
     std::string getServerCertificate(); ///< Wait until server certificates is generated and retrieve it.
     void processAppEvent(grpc::AppEvent const &event); ///< Process an 'App' event.
     void processLoginEvent(grpc::LoginEvent const &event); ///< Process a 'Login' event.

internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCConfig.cpp

@@ -0,0 +1,133 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+
+#include "GRPCConfig.h"
+#include "../Exception/Exception.h"
+
+
+using namespace bridgepp;
+
+
+namespace
+{
+
+Exception const invalidFileException("The service configuration file is invalid"); // Exception for invalid config.
+Exception const couldNotSaveException("The service configuration file could not be saved"); ///< Exception for write errors.
+QString const keyPort = "port"; ///< The JSON key for the port.
+QString const keyCert = "cert"; ///< The JSON key for the TLS certificate.
+QString const keyToken = "token"; ///< The JSON key for the identification token.
+
+
+//****************************************************************************************************************************************************
+/// \brief read a string value from a JSON object.
+///
+/// This function throws an Exception in case of error
+///
+/// \param[in] object The JSON object containing the value.
+/// \param[in] key The key under which the value is stored.
+//****************************************************************************************************************************************************
+QString jsonStringValue(QJsonObject const &object, QString const &key)
+{
+    QJsonValue const v = object[key];
+    if (!v.isString())
+        throw invalidFileException;
+    return v.toString();
+}
+
+
+//****************************************************************************************************************************************************
+/// \brief read a string value from a JSON object.
+///
+/// This function throws an Exception in case of error.
+///
+/// \param[in] object The JSON object containing the value.
+/// \param[in] key The key under which the value is stored.
+//****************************************************************************************************************************************************
+qint32 jsonIntValue(QJsonObject const &object, QString const &key)
+{
+    QJsonValue const v = object[key];
+    if (!v.isDouble())
+        throw invalidFileException;
+    return v.toInt();
+}
+
+
+} // anonymous namespace
+
+
+//****************************************************************************************************************************************************
+/// \param[in] path The path of the file to load from.
+/// \param[out] outError if not null and an error occurs, this variable contains a description of the error.
+/// \return true iff the operation was successful.
+//****************************************************************************************************************************************************
+bool GRPCConfig::load(QString const &path, QString *outError)
+{
+    try
+    {
+        QFile file(path);
+        if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
+            throw Exception("Could not open gRPC service config file.");
+
+        QJsonDocument const doc = QJsonDocument::fromJson(file.readAll());
+        QJsonObject const object = doc.object();
+        port = jsonIntValue(object, keyPort);
+        cert = jsonStringValue(object, keyCert);
+        token = jsonStringValue(object, keyToken);
+
+        return true;
+    }
+    catch (Exception const &e)
+    {
+        if (outError)
+            *outError = e.qwhat();
+        return false;
+    }
+}
+
+
+//****************************************************************************************************************************************************
+/// \param[in] path The path of the file to write to.
+/// \param[out] outError if not null and an error occurs, this variable contains a description of the error.
+/// \return true iff the operation was successful.
+//****************************************************************************************************************************************************
+bool GRPCConfig::save(QString const &path, QString *outError)
+{
+    try
+    {
+        QJsonObject const object;
+        object[keyPort] = port;
+        object[keyCert] = cert;
+        object[keyToken] = token;
+
+        QFile file(path);
+        if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
+            throw couldNotSaveException;
+
+        QByteArray const array = QJsonDocument(object).toJson();
+        if (array.size() != file.write(array))
+            throw couldNotSaveException;
+
+        return true;
+    }
+    catch (Exception const &e)
+    {
+        if (outError)
+            *outError = e.qwhat();
+        return false;
+    }
+}

internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCConfig.h

@@ -0,0 +1,39 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+
+#ifndef BRIDGE_PP_GRPC_CONFIG_H
+#define BRIDGE_PP_GRPC_CONFIG_H
+
+
+//****************************************************************************************************************************************************
+/// Service configuration class.
+//****************************************************************************************************************************************************
+struct GRPCConfig
+{
+public: // data members
+    qint32 port; ///< The port.
+    QString cert; ///< The server TLS certificate.
+    QString token; ///< The identification token.
+
+    bool load(QString const &path, QString *outError = nullptr); ///< Load the service config from file
+    bool save(QString const &path, QString *outError = nullptr); ///< Save the service config to file
+};
+
+
+
+#endif //BRIDGE_PP_GRPC_CONFIG_H

internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCUtils.cpp

@@ -38,6 +38,14 @@ QString serverCertificateFilename()
 }
 
 
+//****************************************************************************************************************************************************
+/// \return the service config file name
+//****************************************************************************************************************************************************
+QString serviceConfigFilename()
+{
+    return "grpcServiceConfig.json";
+}
+
 //****************************************************************************************************************************************************
 //
 //****************************************************************************************************************************************************
@@ -50,6 +58,15 @@ QString serverKeyFilename()
 }
 
 
+//****************************************************************************************************************************************************
+/// \return The absolute path of the service config path.
+//****************************************************************************************************************************************************
+QString serviceConfigPath()
+{
+    return QDir(userConfigDir()).absoluteFilePath(serviceConfigFilename());
+}
+
+
 //****************************************************************************************************************************************************
 /// \return The absolute path of the server certificate.
 //****************************************************************************************************************************************************

internal/frontend/bridge-gui/bridgepp/bridgepp/GRPC/GRPCUtils.h

@@ -31,7 +31,7 @@ namespace bridgepp
 
 typedef std::shared_ptr<grpc::StreamEvent> SPStreamEvent; ///< Type definition for shared pointer to grpc::StreamEvent.
 
-
+QString serviceConfigPath(); ///< Return the path of the service config file.
 QString serverCertificatePath(); ///< Return the path of the server certificate.
 QString serverKeyPath(); ///< Return the path of the server key.
 grpc::LogLevel logLevelToGRPC(Log::Level level); ///< Convert a Log::Level to gRPC enum value.

internal/frontend/frontend.go

@@ -23,6 +23,7 @@ import (
 	"github.com/ProtonMail/proton-bridge/v2/internal/frontend/cli"
 	"github.com/ProtonMail/proton-bridge/v2/internal/frontend/grpc"
 	"github.com/ProtonMail/proton-bridge/v2/internal/frontend/types"
+	"github.com/ProtonMail/proton-bridge/v2/internal/locations"
 	"github.com/ProtonMail/proton-bridge/v2/internal/updater"
 	"github.com/ProtonMail/proton-bridge/v2/pkg/listener"
 )
@@ -45,6 +46,7 @@ func New(
 	updater types.Updater,
 	bridge *bridge.Bridge,
 	restarter types.Restarter,
+	locations *locations.Locations,
 ) Frontend {
 	switch frontendType {
 	case "grpc":
@@ -55,6 +57,7 @@ func New(
 			updater,
 			bridge,
 			restarter,
+			locations,
 		)
 
 	case "cli":

internal/frontend/grpc/config.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+package grpc
+
+import (
+	"encoding/json"
+	"os"
+)
+
+// config is a structure containing the service configuration data that are exchanged by the gRPC server and client.
+type config struct {
+	Port  int    `json:"port"`
+	Cert  string `json:"cert"`  // coming soon
+	Token string `json:"token"` // coming soon
+}
+
+// save saves a gRPC service configuration to file.
+func (s *config) save(path string) error {
+	// Another process may be waiting for this file to be available. In order to prevent this process to open
+	// the file while we are writing in it, we write it with a temp file name, then rename it.
+	tempPath := path + "_"
+	if err := s._save(tempPath); err != nil {
+		return err
+	}
+
+	return os.Rename(tempPath, path)
+}
+
+func (s *config) _save(path string) error {
+	f, err := os.Create(path) //nolint:errcheck,gosec
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = f.Close() }()
+
+	return json.NewEncoder(f).Encode(s)
+}
+
+// load loads a gRPC service configuration from file.
+func (s *config) load(path string) error {
+	f, err := os.Open(path) //nolint:errcheck,gosec
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = f.Close() }()
+
+	return json.NewDecoder(f).Decode(s)
+}

internal/frontend/grpc/config_test.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+package grpc
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+const (
+	dummyPort    = 12
+	dummyCert    = "A dummy cert"
+	dummyToken   = "A dummy token"
+	tempFileName = "test.json"
+)
+
+func TestConfig(t *testing.T) {
+	conf1 := config{
+		Port:  dummyPort,
+		Cert:  dummyCert,
+		Token: dummyToken,
+	}
+
+	// Read-back test
+	tempDir := t.TempDir()
+	tempFilePath := filepath.Join(tempDir, tempFileName)
+	require.NoError(t, conf1.save(tempFilePath))
+
+	conf2 := config{}
+	require.NoError(t, conf2.load(tempFilePath))
+	require.Equal(t, conf1, conf2)
+
+	// failure to load
+	require.Error(t, conf2.load(tempFilePath+"_"))
+
+	// failure to save
+	require.Error(t, conf2.save(filepath.Join(tempDir, "non/existing/folder", tempFileName)))
+}

internal/frontend/grpc/service.go

@@ -22,7 +22,9 @@ package grpc
 import (
 	"context"
 	cryptotls "crypto/tls"
+	"fmt"
 	"net"
+	"path/filepath"
 	"strings"
 	"sync"
 	"time"
@@ -31,6 +33,7 @@ import (
 	"github.com/ProtonMail/proton-bridge/v2/internal/config/settings"
 	"github.com/ProtonMail/proton-bridge/v2/internal/events"
 	"github.com/ProtonMail/proton-bridge/v2/internal/frontend/types"
+	"github.com/ProtonMail/proton-bridge/v2/internal/locations"
 	"github.com/ProtonMail/proton-bridge/v2/internal/updater"
 	"github.com/ProtonMail/proton-bridge/v2/internal/users"
 	"github.com/ProtonMail/proton-bridge/v2/pkg/keychain"
@@ -43,6 +46,10 @@ import (
 	"google.golang.org/protobuf/types/known/emptypb"
 )
 
+const (
+	serviceConfigFileName = "grpcServiceConfig.json"
+)
+
 // Service is the RPC service struct.
 type Service struct { // nolint:structcheck
 	UnimplementedBridgeServer
@@ -68,6 +75,7 @@ type Service struct { // nolint:structcheck
 	initializing       sync.WaitGroup
 	initializationDone sync.Once
 	firstTimeAutostart sync.Once
+	locations          *locations.Locations
 }
 
 // NewService returns a new instance of the service.
@@ -78,6 +86,7 @@ func NewService(
 	updater types.Updater,
 	bridge types.Bridger,
 	restarter types.Restarter,
+	locations *locations.Locations,
 ) *Service {
 	s := Service{
 		UnimplementedBridgeServer: UnimplementedBridgeServer{},
@@ -92,6 +101,7 @@ func NewService(
 		initializing:       sync.WaitGroup{},
 		initializationDone: sync.Once{},
 		firstTimeAutostart: sync.Once{},
+		locations:          locations,
 	}
 
 	// Initializing.Done is only called sync.Once. Please keep the increment
@@ -111,12 +121,18 @@ func NewService(
 
 	RegisterBridgeServer(s.grpcServer, &s)
 
-	s.listener, err = net.Listen("tcp", "127.0.0.1:9292") // Port should be configurable from the command-line.
+	s.listener, err = net.Listen("tcp", "127.0.0.1:0") // Port 0 means that the port is randomly picked by the system.
+
 	if err != nil {
-		s.log.WithError(err).Error("could not create listener")
+		s.log.WithError(err).Panic("could not create listener")
-		panic(err)
 	}
 
+	if err := s.saveGRPCServerConfigFile(); err != nil {
+		s.log.WithError(err).Panic("could not write gRPC service configuration file")
+	}
+
+	s.log.Info("gRPC server listening at ", s.listener.Addr())
+
 	return &s
 }
 
@@ -387,3 +403,19 @@ func (s *Service) installUpdate() {
 
 	_ = s.SendEvent(NewUpdateSilentRestartNeededEvent())
 }
+
+func (s *Service) saveGRPCServerConfigFile() error {
+	address, ok := s.listener.Addr().(*net.TCPAddr)
+	if !ok {
+		return fmt.Errorf("could not retrieve gRPC service listener address")
+	}
+
+	sc := config{Port: address.Port}
+
+	settingsPath, err := s.locations.ProvideSettingsPath()
+	if err != nil {
+		return err
+	}
+
+	return sc.save(filepath.Join(settingsPath, serviceConfigFileName))
+}