Track current db tasks and cancel when suspending

SessionUtilitiesKit/Database/Storage.swift

@@ -91,6 +91,9 @@ open class Storage {
     /// This property gets set the first time we successfully write to the database
     public private(set) var hasSuccessfullyWritten: Bool = false
     
+    /// This property keeps track of all current database tasks and can be used when suspending the database to explicitly
+    /// cancel any currently running tasks
+    @ThreadSafeObject private var currentTasks: Set<Task<(), Never>> = []
     
     // MARK: - Initialization
     
@@ -483,7 +486,12 @@ open class Storage {
         guard !isSuspended else { return }
         
         isSuspended = true
-        Log.info(.storage, "Database access suspended.")
+        Log.info(.storage, "Database access suspended - cancelling \(currentTasks.count) running task(s).")
+        
+        /// Before triggering an `interrupt` (which will forcibly kill in-progress database queries) we want to try to cancel all
+        /// database tasks to give them a small chance to resolve cleanly before we take a brute-force approach
+        currentTasks.forEach { $0.cancel() }
+        _currentTasks.performUpdate { _ in [] }
         
         /// Interrupt any open transactions (if this function is called then we are expecting that all processes have finished running
         /// and don't actually want any more transactions to occur)
@@ -660,6 +668,7 @@ open class Storage {
         let syncQueue = DispatchQueue(label: "com.session.performOperation.syncQueue")
         let semaphore: DispatchSemaphore = DispatchSemaphore(value: 0)
         var operationResult: Result<T, Error>?
+        var operationTask: Task<(), Never>?
         let logErrorIfNeeded: (Result<T, Error>) -> Result<T, Error> = { result in
             switch result {
                 case .success: break
@@ -673,6 +682,7 @@ open class Storage {
         func completeOperation(with result: Result<T, Error>) {
             syncQueue.sync {
                 guard operationResult == nil else { return }
+                info.storage?.removeTask(operationTask)
                 operationResult = result
                 semaphore.signal()
                 
@@ -741,6 +751,10 @@ open class Storage {
             }
         }
         
+        /// Store the task in case we want to
+        info.storage?.addTask(task)
+        operationTask = task
+        
         /// For the `async` operation the returned value should be ignored so just return the `invalidQueryResult` error
         guard !info.isAsync else {
             return (.failure(StorageError.invalidQueryResult), task)
@@ -782,13 +796,24 @@ open class Storage {
                         holder.task = task
                     }
                 }
-                .handleEvents(receiveCancel: { holder.task?.cancel() })
+                .handleEvents(receiveCancel: { [weak self] in
+                    holder.task?.cancel()
+                    self?.removeTask(holder.task)
+                })
                 .eraseToAnyPublisher()
         }
     }
     
     // MARK: - Functions
     
+    private func addTask(_ task: Task<(), Never>) {
+        _currentTasks.performUpdate { $0.inserting(task) }
+    }
+    
+    private func removeTask(_ task: Task<(), Never>?) {
+        _currentTasks.performUpdate { $0.removing(task) }
+    }
+    
     @discardableResult public func write<T>(
         fileName file: String = #file,
         functionName funcN: String = #function,