Fix DynamoDB UpdateExpression syntax error in MarkEventUnprocessed method

[Copilot]

Fixes the Amazon.DynamoDBv2.AmazonDynamoDBException: Invalid UpdateExpression: Syntax error; token: "=", near: "not_processed" error that occurs when using AWS DynamoDB locking features.

Problem

The MarkEventUnprocessed method in DynamoPersistenceProvider.cs was using incorrect DynamoDB UpdateExpression syntax:

UpdateExpression = "ADD not_processed = :n"

The ADD operation in DynamoDB does not use the = operator, causing the UpdateExpression to be invalid and throwing a syntax error during workflow execution.

Solution

Corrected the UpdateExpression syntax by removing the invalid = operator:

UpdateExpression = "ADD not_processed :n"

This follows the proper DynamoDB UpdateExpression syntax where ADD operations directly specify the attribute name followed by the value reference without an equals sign.

Impact

• Resolves the DynamoDB syntax error when marking events as unprocessed
• Fixes workflow execution failures when using UseAwsDynamoLocking configuration
• No breaking changes or API modifications
• Maintains backward compatibility

Closes issue where workflows would fail with DynamoDB UpdateExpression syntax errors during event processing.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Amazon.DynamoDBv2.AmazonDynamoDBException: Invalid UpdateExpression: Syntax error; token: "=", near: "not_processed</issue_title>
<issue_description>Describe the bug
Sometimes during a workflow execution we see the following exception:
Amazon.DynamoDBv2.AmazonDynamoDBException: Invalid UpdateExpression: Syntax error; token: "=", near: "not_processed

To Reproduce
use the following nuget versions:
WorkflowCore 3.6.2
WorkflowCore.Providers.AWS 3.6.0

happens after i configure: UseAwsDynamoLocking in startup.cs

Expected behavior
Should start the workflow

Additional context
Logs:
{"app":"MyApp","timestamp":"2024-11-12T11:52:22.7271646Z","message":"Starting step "WaitFor" on workflow "16f21c6f-4e4c-4636-a196-8d4dfe51234c"","level":"Debug","0":"WaitFor","1":"16f21c6f-4e4c-4636-a196-8d4dfe51234c","category":"WorkflowCore.Services.WorkflowExecutor","threadId":126,"version":"0.1.0+df7b726674aae621f4a6a7b477a91afb45072a98","logVersion":"2"}
{"app":"MyApp","timestamp":"2024-11-12T11:52:23.3639000Z","message":"Subscribing to event "operationCompletedEvent" "AlisTestingLockingZ3" for workflow "16f21c6f-4e4c-4636-a196-8d4dfe51234c" step 1","level":"Debug","0":"operationCompletedEvent","1":"AlisTestingLockingZ3","2":"16f21c6f-4e4c-4636-a196-8d4dfe51234c","3":1,"category":"WorkflowCore.Services.BackgroundTasks.WorkflowConsumer","threadId":77,"version":"0.1.0+df7b726674aae621f4a6a7b477a91afb45072a98","logVersion":"2"}

and then this error is thrown:

Amazon.DynamoDBv2.AmazonDynamoDBException: Invalid UpdateExpression: Syntax error; token: "=", near: "not_processed = :n"\r\n ---> Amazon.Runtime.Internal.HttpErrorResponseException: Exception of type 'Amazon.Runtime.Internal.HttpErrorResponseException' was thrown.\r\n at Amazon.Runtime.HttpWebRequestMessage.ProcessHttpResponseMessage(HttpResponseMessage responseMessage)\r\n at Amazon.Runtime.HttpWebRequestMessage.GetResponseAsync(CancellationToken cancellationToken)\r\n at Amazon.Runtime.Internal.HttpHandler1.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.Unmarshaller.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.ErrorHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n --- End of inner exception stack trace ---\r\n at Amazon.Runtime.Internal.HttpErrorResponseExceptionHandler.HandleExceptionStream(IRequestContext requestContext, IWebResponseData httpErrorResponse, HttpErrorResponseException exception, Stream responseStream)\r\n at Amazon.Runtime.Internal.HttpErrorResponseExceptionHandler.HandleExceptionAsync(IExecutionContext executionContext, HttpErrorResponseException exception)\r\n at Amazon.Runtime.Internal.ExceptionHandler1.HandleAsync(IExecutionContext executionContext, Exception exception)\r\n at Amazon.Runtime.Internal.ErrorHandler.ProcessExceptionAsync(IExecutionContext executionContext, Exception exception)\r\n at Amazon.Runtime.Internal.ErrorHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.CallbackHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.Signer.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.EndpointDiscoveryHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.EndpointDiscoveryHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.CredentialsRetriever.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.RetryHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.RetryHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.XRay.Recorder.Handlers.AwsSdk.Internal.XRayPipelineHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.CallbackHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.CallbackHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.ErrorCallbackHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at Amazon.Runtime.Internal.MetricsHandler.InvokeAsync[T](IExecutionContext executionContext)\r\n at WorkflowCore.Providers.AWS.Services.DynamoPersistenceProvider.MarkEventUnprocessed(String id, CancellationToken cancellationToken)\r\n at WorkflowCore.Services.BackgroundTasks.WorkflowConsumer.SubscribeEvent(EventSubscription subscription, IPersistenceProvider persistenceStore, CancellationToken cancellationToken)\r\n at WorkflowCore.Services.BackgroundTasks.WorkflowConsumer.SubscribeEvent(EventSubscription subscription, IPersistenceProvider persistenceStore, CancellationToken cancellationToken)\r\n at WorkflowCore.Services.BackgroundTasks.WorkflowConsumer.ProcessItem(String itemId, Cancellation...

Fixes #1315

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