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Add protocol for migration service

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This commit is contained in:
Oleksii Zghurskyi
2025-08-07 23:50:00 +03:00
parent 6642523c2b
commit 860f73b731
10 changed files with 448 additions and 208 deletions
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245
Sources/DataRaft/Classes/DatabaseService.swift
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@@ -48,7 +48,69 @@ import DataLiteC
///
/// This approach allows you to build reusable service layers on top of a safe, transactional,
/// and serialized foundation.
open class DatabaseService: DatabaseServiceProtocol {
///
/// ## Error Handling
///
/// All database access is serialized using an internal dispatch queue to ensure thread safety.
/// If a database corruption or decryption failure is detected (e.g., `SQLITE_NOTADB`), the
/// service attempts to re-establish the connection and, in case of transaction blocks,
/// retries the entire transaction block exactly once. If the problem persists, the error
/// is rethrown.
///
/// ## Encryption Key Management
///
/// If a `keyProvider` is set, the service will use it to retrieve and apply encryption keys
/// when establishing or re-establishing a database connection. Any error that occurs while
/// retrieving or applying the encryption key is reported to the provider via
/// `databaseService(_:didReceive:)`. Non-encryption-related errors (e.g., file access
/// issues) are not reported to the provider.
///
/// ## Reconnect Behavior
///
/// The service can automatically reconnect to the database, but this happens only in very specific
/// circumstances. Reconnection is triggered only when you run a transactional operation using
/// ``perform(in:closure:)``, and a decryption error (`SQLITE_NOTADB`) occurs during
/// the transaction. Even then, reconnection is possible only if you have set a ``keyProvider``,
/// and only if the provider allows it by returning `true` from its
/// ``DatabaseServiceKeyProvider/databaseServiceShouldReconnect(_:)-84qfz``
/// method.
///
/// When this happens, the service will ask the key provider for a new encryption key, create a new
/// database connection, and then try to re-run your transaction block one more time. If the second
/// attempt also fails with the same decryption error, or if reconnection is not allowed, the error is
/// returned to your code as usual, and no further attempts are made.
///
/// It's important to note that reconnection and retrying of transactions never happens outside of
/// transactional operations, and will never be triggered for other types of errors. All of this logic
/// runs on the service’s internal queue, so you don’t have to worry about thread safety.
///
/// - Important: Because a transaction block can be executed more than once when this
/// mechanism is triggered, make sure that your block is idempotent and doesn't cause any
/// side effects outside the database itself.
///
/// ## Topics
///
/// ### Initializers
///
/// - ``init(provider:queue:)``
/// - ``init(connection:queue:)``
///
/// ### Key Management
///
/// - ``DatabaseServiceKeyProvider``
/// - ``keyProvider``
///
/// ### Connection Management
///
/// - ``ConnectionProvider``
/// - ``reconnect()``
///
/// ### Database Operations
///
/// - ``DatabaseServiceProtocol/Perform``
/// - ``perform(_:)``
/// - ``perform(in:closure:)``
open class DatabaseService: DatabaseServiceProtocol, @unchecked Sendable {
/// A closure that provides a new database connection when invoked.
///
/// `ConnectionProvider` is used to defer the creation of a `Connection` instance
@@ -62,58 +124,33 @@ open class DatabaseService: DatabaseServiceProtocol {
// MARK: - Properties
private let provider: ConnectionProvider
private var connection: Connection
private let queue: DispatchQueue
private let queueKey = DispatchSpecificKey<Void>()
private var connection: Connection
/// The object that provides the encryption key for the database connection.
/// Provides the encryption key for the database connection.
///
/// When this property is set, the service attempts to retrieve an encryption key from the
/// provider and apply it to the current database connection. This operation is performed
/// synchronously on the service’s internal queue to ensure thread safety.
/// When this property is set, the service synchronously retrieves and applies an encryption
/// key from the provider to the current database connection on the service’s internal queue,
/// ensuring thread safety.
///
/// If an error occurs during key retrieval or application, the service notifies the provider
/// by calling `databaseService(_:didReceive:)`.
/// If an error occurs during key retrieval or application (for example, if biometric
/// authentication is cancelled, the key is unavailable, or decryption fails due to an
/// incorrect key), the service notifies the provider by calling
/// ``DatabaseServiceKeyProvider/databaseService(_:didReceive:)-xbrk``.
///
/// This enables external management of encryption keys, including features such as key rotation,
/// user-scoped encryption, or error handling delegation.
///
/// - Important: The service does not retry failed key applications. Ensure the provider is
/// correctly configured and able to supply a valid key when needed.
/// This mechanism enables external management of encryption keys, supporting scenarios such
/// as key rotation, user-specific encryption, or custom error handling.
public weak var keyProvider: DatabaseServiceKeyProvider? {
didSet {
perform { connection in
do {
if let key = try keyProvider?.databaseServiceKey(self) {
try connection.apply(key)
}
} catch {
keyProvider?.databaseService(self, didReceive: error)
}
withConnection { connection in
try? applyKey(to: connection)
}
}
}
// MARK: - Inits
/// Creates a new `DatabaseService` using the given connection provider and optional queue.
///
/// This convenience initializer wraps the provided autoclosure in a `ConnectionProvider`
/// and delegates to the designated initializer. It is useful when passing a simple
/// connection expression.
///
/// - Parameters:
/// - provider: A closure that returns a `Connection` instance and may throw.
/// - queue: An optional dispatch queue used as a target for internal serialization. If `nil`,
/// a default serial queue with `.utility` QoS is created internally.
/// - Throws: Rethrows any error thrown by the connection provider.
public convenience init(
connection provider: @escaping @autoclosure ConnectionProvider,
queue: DispatchQueue? = nil
) rethrows {
try self.init(provider: provider, queue: queue)
}
/// Creates a new `DatabaseService` with the specified connection provider and dispatch queue.
///
/// This initializer immediately invokes the `provider` closure to establish the initial database
@@ -139,85 +176,88 @@ open class DatabaseService: DatabaseServiceProtocol {
}
}
/// Creates a new `DatabaseService` using the given connection provider and optional queue.
///
/// This convenience initializer wraps the provided autoclosure in a `ConnectionProvider`
/// and delegates to the designated initializer. It is useful when passing a simple
/// connection expression.
///
/// - Parameters:
/// - provider: A closure that returns a `Connection` instance and may throw.
/// - queue: An optional dispatch queue used as a target for internal serialization. If `nil`,
/// a default serial queue with `.utility` QoS is created internally.
/// - Throws: Rethrows any error thrown by the connection provider.
public convenience init(
connection provider: @escaping @autoclosure ConnectionProvider,
queue: DispatchQueue? = nil
) rethrows {
try self.init(provider: provider, queue: queue)
}
// MARK: - Methods
/// Re-establishes the database connection using the stored connection provider.
///
/// This method creates a new `Connection` instance by invoking the original provider. If a
/// `keyProvider` is set, the method attempts to retrieve and apply an encryption key to the new
/// connection. The new connection replaces the existing one.
/// This method synchronously creates a new ``Connection`` instance by invoking the original
/// provider on the service’s internal queue. If a ``keyProvider`` is set, the service attempts
/// to retrieve and apply an encryption key to the new connection.
/// If any error occurs during key retrieval or application, the provider is notified via
/// ``DatabaseServiceKeyProvider/databaseService(_:didReceive:)-xbrk``,
/// and the error is rethrown.
///
/// The operation is executed synchronously on the internal dispatch queue via `perform(_:)`
/// The new connection replaces the existing one only if all steps succeed without errors.
///
/// This operation is always executed on the internal dispatch queue (see ``perform(_:)``)
/// to ensure thread safety.
///
/// - Throws: Any error thrown during connection creation or while retrieving or applying the
/// encryption key.
/// - Throws: Any error thrown during connection creation or while retrieving or applying
/// the encryption key. Only encryption-related errors are reported to the ``keyProvider``.
public func reconnect() throws {
try perform { _ in
try withConnection { _ in
let connection = try provider()
if let key = try keyProvider?.databaseServiceKey(self) {
try connection.apply(key)
}
try applyKey(to: connection)
self.connection = connection
}
}
/// Executes the given closure using the active database connection.
///
/// This method ensures thread-safe access to the underlying `Connection` by synchronizing
/// execution on an internal serial dispatch queue. If the call is already on that queue, the
/// closure is executed directly to avoid unnecessary dispatching.
///
/// If the closure throws a `SQLiteError` with code `SQLITE_NOTADB` (e.g., when the database file
/// is corrupted or invalid), the service attempts to re-establish the connection by calling
/// ``reconnect()``. The error is still rethrown after reconnection.
/// Ensures thread-safe access to the underlying ``Connection`` by synchronizing execution on
/// the service’s internal serial dispatch queue. If the call is already running on this queue,
/// the closure is executed directly to avoid unnecessary dispatching.
///
/// - Parameter closure: A closure that takes the active connection and returns a result.
/// - Returns: The value returned by the closure.
/// - Throws: Any error thrown by the closure or during reconnection logic.
/// - Throws: Any error thrown by the closure.
public func perform<T>(_ closure: Perform<T>) rethrows -> T {
do {
switch DispatchQueue.getSpecific(key: queueKey) {
case .none: return try queue.asyncAndWait { try closure(connection) }
case .some: return try closure(connection)
}
} catch {
switch error {
case let error as Connection.Error:
if error.code == SQLITE_NOTADB {
try reconnect()
}
fallthrough
default:
throw error
}
}
try withConnection(closure)
}
/// Executes a closure inside a transaction if the connection is in autocommit mode.
///
/// If the current connection is in autocommit mode, a new transaction of the specified type
/// is started, and the closure is executed within it. If the closure completes successfully,
/// the transaction is committed. If an error is thrown, the transaction is rolled back.
/// If the connection is in autocommit mode, starts a new transaction of the specified type,
/// executes the closure within it, and commits the transaction on success. If the closure
/// throws, the transaction is rolled back.
///
/// If the thrown error is a `SQLiteError` with code `SQLITE_NOTADB`, the service attempts to
/// reconnect and retries the entire transaction block exactly once.
/// If the closure throws a `Connection.Error` with code `SQLITE_NOTADB` and reconnecting is
/// allowed, the service attempts to reconnect and retries the entire transaction block once.
///
/// If the connection is already within a transaction (i.e., not in autocommit mode),
/// the closure is executed directly without starting a new transaction.
/// If already inside a transaction (not in autocommit mode), executes the closure directly
/// without starting a new transaction.
///
/// - Parameters:
/// - transaction: The type of transaction to begin (e.g., `deferred`, `immediate`, `exclusive`).
/// - transaction: The type of transaction to begin.
/// - closure: A closure that takes the active connection and returns a result.
/// - Returns: The value returned by the closure.
/// - Throws: Any error thrown by the closure, transaction control statements,
/// or reconnect logic.
/// - Throws: Any error thrown by the closure, transaction control statements, or reconnect logic.
///
/// - Important: The closure may be executed more than once. Ensure it is idempotent.
public func perform<T>(
in transaction: TransactionType,
closure: Perform<T>
) rethrows -> T {
if connection.isAutocommit {
try perform { connection in
try withConnection { connection in
if connection.isAutocommit {
do {
try connection.beginTransaction(transaction)
let result = try closure(connection)
@@ -226,12 +266,13 @@ open class DatabaseService: DatabaseServiceProtocol {
} catch {
try connection.rollbackTransaction()
guard let error = error as? Connection.Error,
error.code == SQLITE_NOTADB
error.code == SQLITE_NOTADB,
shouldReconnect
else { throw error }
try reconnect()
return try perform { connection in
return try withConnection { connection in
do {
try connection.beginTransaction(transaction)
let result = try closure(connection)
@@ -243,9 +284,35 @@ open class DatabaseService: DatabaseServiceProtocol {
}
}
}
} else {
return try closure(connection)
}
} else {
try perform(closure)
}
}
}
private extension DatabaseService {
var shouldReconnect: Bool {
keyProvider?.databaseServiceShouldReconnect(self) ?? false
}
func withConnection<T>(_ closure: Perform<T>) rethrows -> T {
switch DispatchQueue.getSpecific(key: queueKey) {
case .none: try queue.asyncAndWait { try closure(connection) }
case .some: try closure(connection)
}
}
func applyKey(to connection: Connection) throws {
do {
if let key = try keyProvider?.databaseServiceKey(self) {
let sql = "SELECT count(*) FROM sqlite_master"
try connection.apply(key)
try connection.execute(raw: sql)
}
} catch {
keyProvider?.databaseService(self, didReceive: error)
throw error
}
}
}