How to cancel a running trigger function within azure durable functions? - azure

Question

I am trying the fan-out, fan-in pattern. Here's my code
[FunctionName("af_cancellation")]
public static async Task<string> RunOrchestrator(
[OrchestrationTrigger] DurableOrchestrationContext context, ILogger log)
{
var taskList = new List<Task<string>>();
var tokenSource = new CancellationTokenSource();
taskList.Add(context.CallActivityAsync<string>("af_cancellation_Hello", new { ct = tokenSource.Token, city = "Tokyo" }));
taskList.Add(context.CallActivityAsync<string>("af_cancellation_Hello", new { ct = tokenSource.Token, city = "Seattle" }));
taskList.Add(context.CallActivityAsync<string>("af_cancellation_Hello", new { ct = tokenSource.Token, city = "London" }));
try
{
await Task.WhenAll(taskList);
}
catch (FunctionException)
{
log.LogError("trigger function failed");
tokenSource.Cancel();
}
string output = "";
foreach (var t in taskList)
{
output += t.Result;
}
return output;
}
I would like to cancel all the tasks in taskList if any of them throw an exception. What i am noticing is that await Task.WhenAll finishes all the tasks before moving forward.
Here's the sample trigger function
[FunctionName("af_cancellation_Hello")]
public static string SayHello([ActivityTrigger] DurableActivityContext context, ILogger log)
{
var data = context.GetInput<dynamic>();
var name = (string)data.city;
// unable to de-serialize cancellation token here but we'll ignore that.
var ct = JsonConvert.DeserializeObject<CancellationToken>(data.ct);
if (name != "London")
{
System.Threading.Thread.Sleep(1000 * 30);
}
else
{
System.Threading.Thread.Sleep(1000 * 10);
throw new FunctionException("don't like london");
}
log.LogInformation($"Saying hello to {name}.");
return $"Hello {name}!";
}
How can i achieve this?

Answer 1

According to this I think it's not possible. If you need to undo the job from the other activities that succeeded, you must take a look on the Saga Pattern and launch compensating activities.
more info:
https://microservices.io/patterns/data/saga.html
https://www.enterpriseintegrationpatterns.com/patterns/conversation/CompensatingAction.html