Merge pull request #9 from swift-sprinter/feature/optimistic_lock

Add optimistic locking support

Author: Andrea-Scuderi

Example/BreezeItemAPI/Package.swift

@@ -12,7 +12,7 @@ let package = Package(
         .executable(name: "ItemAPI", targets: ["ItemAPI"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/swift-sprinter/Breeze.git", from: "0.1.0")
+        .package(url: "https://github.com/swift-sprinter/Breeze.git", from: "0.2.0")
     ],
     targets: [
         .executableTarget(

Package.resolved

@@ -25,7 +25,7 @@ let package = Package(
     dependencies: [
         .package(url: "https://github.com/swift-server/swift-aws-lambda-runtime.git", from: "1.0.0-alpha.1"),
         .package(url: "https://github.com/swift-server/swift-aws-lambda-events.git", from: "0.1.0"),
-        .package(url: "https://github.com/soto-project/soto.git", from: "6.0.0"),
+        .package(url: "https://github.com/soto-project/soto.git", from: "6.7.0"),
         .package(url: "https://github.com/apple/swift-log.git", from: "1.0.0"),
         .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.0.0"),
         .package(url: "https://github.com/stencilproject/Stencil.git", from: "0.15.1"),

Package.swift

@@ -69,6 +69,12 @@ All you need to do is to decide the struct conforming `BreezeCodable` to persist
 
 Each lambda will be initialized with a specific `_HANDLER` and it will run the code to implement the required logic needed by one of the CRUD functions. The code needs to be packaged and deployed using the referenced architecture.
 
+### Optimistic locking
+
+Optimistic locking is a strategy to ensure that the BreezeCodable Item is not updated by another request before updating or deleting it.
+The fields `updatedAt` and `createdAt` are used to implement optimistic locking.
+Refer to the [DynamoDB documentation](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.OptimisticLocking.html) for more details.
+
 ## Lambda package with Swift Package Manager
 
 To package the Lambda is required to create a Swift Package using the following `Package.swift` file.
@@ -88,7 +94,7 @@ let package = Package(
         .executable(name: "ItemAPI", targets: ["ItemAPI"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/swift-sprinter/Breeze.git", from: "0.1.0"),
+        .package(url: "https://github.com/swift-sprinter/Breeze.git", from: "0.2.0"),
     ],
     targets: [
         .executableTarget(
@@ -146,7 +152,7 @@ OPTIONS:
 Define a configuration file with the following format:
 ```yml
 service: swift-breeze-rest-item-api
- awsRegion: us_east_1
+ awsRegion: us-east-1
  swiftVersion: 5.7.3
  swiftConfiguration: release
  packageName: BreezeItemAPI
@@ -199,7 +205,7 @@ output:
 /Users/andreascuderi/Documents/workspace/Breeze/Sources/BreezeCommand/Resources/breeze.yml
 
 service: swift-breeze-rest-item-api
-awsRegion: us_east_1
+awsRegion: us-east-1
 swiftVersion: 5.7.3
 swiftConfiguration: release
 packageName: BreezeItemAPI
@@ -303,12 +309,12 @@ Returns the updated `BreezeCodable`.
 
 - `delete`
 
-Gets the value of the `BreezeCodable.key` from the `APIGatewayV2Request.pathParameters` dictionary and calls `deleteItem` on `BreezeDynamoDBService`.
+Gets the value of the `BreezeCodable.key` from the `APIGatewayV2Request.pathParameters` dictionary, the value of `updatedAt` and `createdAt` from `APIGatewayV2Request.queryStringParameters` dictionary and calls `deleteItem` on `BreezeDynamoDBService`.
 Returns the `BreezeCodable` if persisted on DynamoDB.
 
 - `list`
 
-Gets the value of the `exclusiveStartKey` and `limit` from the `APIGatewayV2Request.pathParameters` dictionary and calls `listItems` on `BreezeDynamoDBService`.
+Gets the value of the `exclusiveStartKey` and `limit` from the `APIGatewayV2Request.queryStringParameters` dictionary and calls `listItems` on `BreezeDynamoDBService`.
 Returns the `ListResponse` containing the items if persisted on DynamoDB.
 
 ```swift

README.md

@@ -12,7 +12,7 @@ let package = Package(
         .executable(name: "{{ params.targetName }}", targets: ["{{ params.targetName }}"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/swift-sprinter/Breeze.git", from: "0.1.0")
+        .package(url: "https://github.com/swift-sprinter/Breeze.git", from: "0.2.0")
     ],
     targets: [
         .executableTarget(

Sources/BreezeCommand/Resources/Template/SwiftPackage/Package.swift.stencil

@@ -1,5 +1,5 @@
 service: swift-breeze-rest-item-api
-awsRegion: us_east_1
+awsRegion: us-east-1
 swiftVersion: 5.7.3
 swiftConfiguration: release
 packageName: BreezeItemAPI

Sources/BreezeCommand/Resources/breeze-sign-in-with-apple.yml

@@ -1,5 +1,5 @@
 service: swift-breeze-rest-item-api
-awsRegion: us_east_1
+awsRegion: us-east-1
 swiftVersion: 5.7.3
 swiftConfiguration: release
 packageName: BreezeItemAPI

Sources/BreezeCommand/Resources/breeze.yml

@@ -19,6 +19,7 @@ import SotoDynamoDB
 public class BreezeDynamoDBService: BreezeDynamoDBServing {
     enum ServiceError: Error {
         case notFound
+        case missingParameters
     }
 
     let db: DynamoDB
@@ -39,6 +40,8 @@ public extension BreezeDynamoDBService {
         item.createdAt = date.iso8601
         item.updatedAt = date.iso8601
         let input = DynamoDB.PutItemCodableInput(
+            conditionExpression: "attribute_not_exists(#keyName)",
+            expressionAttributeNames: ["#keyName": keyName],
             item: item,
             tableName: tableName
         )
@@ -58,12 +61,19 @@ public extension BreezeDynamoDBService {
         return item
     }
 
+    private struct AdditionalAttributes: Encodable {
+        let oldUpdatedAt: String
+    }
+    
     func updateItem<T: BreezeCodable>(item: T) async throws -> T {
         var item = item
+        let oldUpdatedAt = item.updatedAt ?? ""
         let date = Date()
         item.updatedAt = date.iso8601
-        let input = DynamoDB.UpdateItemCodableInput(
-            conditionExpression: "attribute_exists(createdAt)",
+        let attributes = AdditionalAttributes(oldUpdatedAt: oldUpdatedAt)
+        let input = try DynamoDB.UpdateItemCodableInput(
+            additionalAttributes: attributes,
+            conditionExpression: "attribute_exists(#\(keyName)) AND #updatedAt = :oldUpdatedAt AND #createdAt = :createdAt",
             key: [keyName],
             tableName: tableName,
             updateItem: item
@@ -72,9 +82,19 @@ public extension BreezeDynamoDBService {
         return try await readItem(key: item.key)
     }
 
-    func deleteItem(key: String) async throws {
+    func deleteItem<T: BreezeCodable>(item: T) async throws {
+        guard let updatedAt = item.updatedAt,
+              let createdAt = item.createdAt else {
+            throw ServiceError.missingParameters
+        }
+        
         let input = DynamoDB.DeleteItemInput(
-            key: [keyName: DynamoDB.AttributeValue.s(key)],
+            conditionExpression: "#updatedAt = :updatedAt AND #createdAt = :createdAt",
+            expressionAttributeNames: ["#updatedAt": "updatedAt",
+                                       "#createdAt" : "createdAt"],
+            expressionAttributeValues: [":updatedAt": .s(updatedAt),
+                                        ":createdAt" : .s(createdAt)],
+            key: [keyName: DynamoDB.AttributeValue.s(item.key)],
             tableName: tableName
         )
         let _ = try await db.deleteItem(input)

Sources/BreezeDynamoDBService/BreezeDynamoDBService.swift

@@ -20,6 +20,6 @@ public protocol BreezeDynamoDBServing {
     func createItem<Item: BreezeCodable>(item: Item) async throws -> Item
     func readItem<Item: BreezeCodable>(key: String) async throws -> Item
     func updateItem<Item: BreezeCodable>(item: Item) async throws -> Item
-    func deleteItem(key: String) async throws
+    func deleteItem<Item: BreezeCodable>(item: Item) async throws
     func listItems<Item: BreezeCodable>(key: String?, limit: Int?) async throws -> ListResponse<Item>
 }

Sources/BreezeDynamoDBService/BreezeDynamoDBServing.swift

@@ -81,14 +81,23 @@ struct BreezeLambdaHandler<T: BreezeCodable> {
             return APIGatewayV2Response(with: error, statusCode: .notFound)
         }
     }
+    
+    struct SimpleItem: BreezeCodable {
+        var key: String
+        var createdAt: String?
+        var updatedAt: String?
+    }
 
     func deleteLambdaHandler(context: AWSLambdaRuntimeCore.LambdaContext, event: APIGatewayV2Request) async -> APIGatewayV2Response {
-        guard let key = event.pathParameters?[keyName] else {
+        guard let key = event.pathParameters?[keyName],
+              let createdAt = event.queryStringParameters?["createdAt"],
+              let updatedAt = event.queryStringParameters?["updatedAt"] else {
             let error = BreezeLambdaAPIError.invalidRequest
             return APIGatewayV2Response(with: error, statusCode: .forbidden)
         }
         do {
-            try await self.service.deleteItem(key: key)
+            let simpleItem = SimpleItem(key: key, createdAt: createdAt, updatedAt: updatedAt)
+            try await self.service.deleteItem(item: simpleItem)
             return APIGatewayV2Response(with: BreezeEmptyResponse(), statusCode: .ok)
         } catch {
             return APIGatewayV2Response(with: error, statusCode: .notFound)