Wait for signal to start activity (amazon Workflow)

Question

I have built a workflow using java flow framework provided by AWS. I have created 4 activities. First activity wait for signal to start. Then all the activities execute synchronously using Promise<> object. Workflow implementation code is following-

public class PaginationWorkflowImpl implements PaginationWorkflow 
{  
private ManualUploadClient operations0 = new ManualUploadClientImpl();
   private DownloadActivityClient operations1 = new DownloadActivityClientImpl();
   private ConvertActivityClient operations2 = new ConvertActivityClientImpl();
   private UploadActivityClient operations3 = new UploadActivityClientImpl();
   final Settable<String> result = new Settable<String>();

   public void paginate() 
   {
     Promise<String> UDone = operations0.Upload(result);
     Promise<String> dnDone = operations1.s3Download(UDone);
     Promise<String> convDone = operations2.pdfToTiff(dnDone);
     operations3.s3Upload(convDone);
   }

   @Override
   public void signal1(String data)  {
      // result.set(data);
       //result.Void();
       Promise<String> ready = Promise.asPromise("ready");
       result.chain(ready);
   }


}

Here activity Upload wait for the object result to be in ready state. So when I signal workflow the method signal1 kicks off and puts the object in ready state. But as soon as I signal the workflow, workflow execution get failed.

I am using nodejs aws api to signal workflow. Below is the code for the same-

var AWS = require('aws-sdk');
AWS.config.update({accessKeyId: '', secretAccessKey: ''});
AWS.config.update({region: 'us-east-1'});

var swf = new AWS.SWF();
var params = {
  domain: 'HWdemo2', /* required */
  signalName: 'signal1', /* required */
  workflowId: 'PaginationWorkflow', /* required */
  //input: 'true'
  //runId: 'STRING_VALUE'
};
swf.signalWorkflowExecution(params, function(err, data) {
  if (err) console.log(err, err.stack); // an error occurred
  else     console.log(data);           // successful response
});

And the error which I is showing in AWS workflow events console for execution fail is following-

 ["java.util.concurrent.CancellationException", { "cause": ["java.lang.NullPointerException", { "cause": null, "stackTrace": [{ "methodName": "<init>", "fileName": null, "lineNumber": -1, "className": "java.io.StringReader", "nativeMethod": false }, { "methodName": "createParser", "fileName": "JsonFactory.java", "lineNumber": 835, "className": "com.fasterxml.jackson.core.JsonFactory", "nativeMethod": false }, { "methodName": "readValue", "fileName": "ObjectMapper.java", "lineNumber": 2098, "className": "com.fasterxml.jackson.databind.ObjectMapper", "nativeMethod": false }, { "methodName": "fromData", "fileName": "JsonDataConverter.java", "lineNumber": 96, "className": "com.amazonaws.services.simpleworkflow.flow.JsonDataConverter", "nativeMethod": false }, { "methodName": "signalRecieved", "fileName": "POJOWorkflowDefinition.java", "lineNumber": 111, "className": "com.amazonaws.services.simpleworkflow.flow.pojo.POJOWorkflowDefinition", "nativeMethod": false }, { "methodName": "doExecute", "fileName": "AsyncDecider.java", "lineNumber": 417, "className": "com.amazonaws.services.simpleworkflow.flow.worker.AsyncDecider$1", "nativeMethod": false }, { "methodName": "", "fileName": "", "lineNumber": 0, "className": "--- continuation ---", "nativeMethod": false }, { "methodName": "handleWorkflowExecutionSignaled", "fileName": "AsyncDecider.java", "lineNumber": 413, "className": "com.amazonaws.services.simpleworkflow.flow.worker.AsyncDecider", "nativeMethod": false }, { "methodName": "processEvent", "fileName": "AsyncDecider.java", "lineNumber": 251, "className": "com.amazonaws.services.simpleworkflow.flow.worker.AsyncDecider", "nativeMethod": false }, { "methodName": "decide", "fileName": "AsyncDecider.java", "lineNumber": 496, "className": "com.amazonaws.services.simpleworkflow.flow.worker.AsyncDecider", "nativeMethod": false }, { "methodName": "handleDecisionTask", "fileName": "AsyncDecisionTaskHandler.java", "lineNumber": 50, "className": "com.amazonaws.services.simpleworkflow.flow.worker.AsyncDecisionTaskHandler", "nativeMethod": false }, { "methodName": "pollAndProcessSingleTask", "fileName": "DecisionTaskPoller.java", "lineNumber": 201, "className": "com.amazonaws.services.simpleworkflow.flow.worker.DecisionTaskPoller", "nativeMethod": false }, { "methodName": "run", "fileName": "GenericWorker.java", "lineNumber": 94, "className": "com.amazonaws.services.simpleworkflow.flow.worker.GenericWorker$PollServiceTask", "nativeMethod": false }, { "methodName": "runWorker", "fileName": null, "lineNumber": -1, "className": "java.util.concurrent.ThreadPoolExecutor", "nativeMethod": false }, { "methodName": "run", "fileName": null, "lineNumber": -1, "className": "java.util.concurrent.ThreadPoolExecutor$Worker", "nativeMethod": false }, { "methodName": "run", "fileName": null, "lineNumber": -1, "className": "java.lang.Thread", "nativeMethod": false }], "message": null, "localizedMessage": null, "suppressed": ["[Ljava.lang.Throwable;", []] }], "stackTrace": [{ "methodName": "execute", "fileName": "POJOWorkflowDefinition.java", "lineNumber": 66, "className": "com.amazonaws.services.simpleworkflow.flow.pojo.POJOWorkflowDefinition", "nativeMethod": false }, { "methodName": "doAsync", "fileName": "AsyncDecider.java", "lineNumber": 70, "className": "com.amazonaws.services.simpleworkflow.flow.worker.AsyncDecider$WorkflowExecuteAsyncScope", "nativeMethod": false }], "message": null, "localizedMessage": null, "suppressed": ["[Ljava.lang.Throwable;", []] }] 

Can anyone please help me out with this error, Thanks a lot in advance.

Answer 1

By default workflow execution fails if it cannot deserialize the signal arguments. By default JsonDataConverter is used by workflow decider which is implemented on top of Jackson . It expects JSON document in a specific format. The simplest way to learn this format is to send signal using the generated Java interface and look at the workflow history. Then you can just reproduce it in your JavaScript code.

Answer 2

工作流期望输入对象数组，该对象数组可以转换为json字符串。