Restore the ability to set loggers per-SyncManager (#6400)

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Enhancements
 * <New feature description> (PR [#????](https://github.com/realm/realm-core/pull/????))
 * Expose `Results::is_valid()` in the C API, in order to prevent to use an invalid Results. (PR [#6407](https://github.com/realm/realm-core/pull/6407))
+* Restore `SyncManager::set_logger_factory()` to enable setting different loggers for different SyncManagers ([PR #6400](https://github.com/realm/realm-core/pull/6400)).
 
 ### Fixed
 * `SyncSession::pause()` could hold a reference to the database open after shutting down the sync session, preventing users from being able to delete the realm. ([#6372](https://github.com/realm/realm-core/issues/6372), since v13.3.0)

src/realm/object-store/sync/app.cpp

@@ -260,7 +260,6 @@ App::~App() {}
 
 void App::configure(const SyncClientConfig& sync_client_config)
 {
-    init_logger();
     auto sync_route = make_sync_route(m_app_route);
     m_sync_manager->configure(shared_from_this(), sync_route, sync_client_config);
     if (auto metadata = m_sync_manager->app_metadata()) {
@@ -272,7 +271,7 @@ void App::configure(const SyncClientConfig& sync_client_config)
 bool App::init_logger()
 {
     if (!m_logger_ptr) {
-        m_logger_ptr = util::Logger::get_default_logger();
+        m_logger_ptr = m_sync_manager->get_logger();
     }
     return bool(m_logger_ptr);
 }

src/realm/object-store/sync/sync_manager.cpp

@@ -275,9 +275,36 @@ void SyncManager::reset_for_testing()
     }
 }
 
+void SyncManager::set_log_level(util::Logger::Level level) noexcept
+{
+    util::CheckedLockGuard lock(m_mutex);
+    m_config.log_level = level;
+    // Update the level threshold in the already created logger
+    if (m_logger_ptr) {
+        m_logger_ptr->set_level_threshold(level);
+    }
+}
+
+void SyncManager::set_logger_factory(SyncClientConfig::LoggerFactory factory)
+{
+    util::CheckedLockGuard lock(m_mutex);
+    m_config.logger_factory = std::move(factory);
+
+    if (m_sync_client)
+        throw std::logic_error("Cannot set the logger factory after creating the sync client");
+
+    // Create a new logger using the new factory
+    do_make_logger();
+}
+
 void SyncManager::do_make_logger()
 {
-    m_logger_ptr = util::Logger::get_default_logger();
+    if (m_config.logger_factory) {
+        m_logger_ptr = m_config.logger_factory(m_config.log_level);
+    }
+    else {
+        m_logger_ptr = util::Logger::get_default_logger();
+    }
 }
 
 const std::shared_ptr<util::Logger>& SyncManager::get_logger() const
@@ -306,6 +333,12 @@ void SyncManager::reconnect() const
     }
 }
 
+util::Logger::Level SyncManager::log_level() const noexcept
+{
+    util::CheckedLockGuard lock(m_mutex);
+    return m_config.log_level;
+}
+
 bool SyncManager::perform_metadata_update(util::FunctionRef<void(SyncMetadataManager&)> update_function) const
 {
     util::CheckedLockGuard lock(m_file_system_mutex);

src/realm/object-store/sync/sync_manager.hpp

@@ -75,6 +75,9 @@ struct SyncClientConfig {
     MetadataMode metadata_mode = MetadataMode::Encryption;
     util::Optional<std::vector<char>> custom_encryption_key;
 
+    using LoggerFactory = std::function<std::shared_ptr<util::Logger>(util::Logger::Level)>;
+    LoggerFactory logger_factory;
+    util::Logger::Level log_level = util::Logger::Level::info;
     ReconnectMode reconnect_mode = ReconnectMode::normal; // For internal sync-client testing only!
     bool multiplex_sessions = false;
 
@@ -121,6 +124,13 @@ class SyncManager : public std::enable_shared_from_this<SyncManager> {
     // Destroys the sync manager, terminates all sessions created by it, and stops its SyncClient.
     ~SyncManager();
 
+    // Sets the log level for the Sync Client.
+    // The log level can only be set up until the point the Sync Client is
+    // created (when the first Session is created) or an App operation is
+    // performed (e.g. log in).
+    void set_log_level(util::Logger::Level) noexcept REQUIRES(!m_mutex);
+    void set_logger_factory(SyncClientConfig::LoggerFactory) REQUIRES(!m_mutex);
+
     // Sets the application level user agent string.
     // This should have the format specified here:
     // https://github.com/realm/realm-sync/blob/develop/src/realm/sync/client.hpp#L126 The user agent can only be set
@@ -140,6 +150,7 @@ class SyncManager : public std::enable_shared_from_this<SyncManager> {
     /// on a per-session basis.
     void reconnect() const REQUIRES(!m_session_mutex);
 
+    util::Logger::Level log_level() const noexcept REQUIRES(!m_mutex);
 
     std::vector<std::shared_ptr<SyncSession>> get_all_sessions() const REQUIRES(!m_session_mutex);
     std::shared_ptr<SyncSession> get_session(std::shared_ptr<DB> db, const RealmConfig& config)