Invalid continuation token in GetStatusAsync API

[f2bo]

Description

The new paged GetStatusAsync API appears to return an invalid continuation token when there are no more results.

Expected behavior

The behavior is not documented, and I hadn't used this overload previously so this may be a bad assumption on my part, but I expected GetStatusAsync to return a null continuation token once it completes the enumeration.

Actual behavior

Instead, it returns "bnVsbA==", which when base64 decoded corresponds to "null" as a string.

The loop in the following method never exits because the ContinuationToken is never null. The first iteration of the loop returns the expected results (2 in my test case) and "bnVsbA==" as the continuation token. Then it just keeps returning the same results in subsequent iterations.

private async Task<IEnumerable<string>> GetChildOrchestrations(
    IDurableOrchestrationClient client,
    string instanceIdPrefix,
    CancellationToken cancellationToken = default)
{
    var children = new List<string>();

    var queryCondition = new OrchestrationStatusQueryCondition
    {
        InstanceIdPrefix = instanceIdPrefix,
        ShowInput = false,
        ContinuationToken = null
    };

    do
    {
        var status = await client.GetStatusAsync(queryCondition, cancellationToken);
        queryCondition.ContinuationToken = status.ContinuationToken;

        children.AddRange(status.DurableOrchestrationState.Select(p => p.InstanceId));
    } while (queryCondition.ContinuationToken != null && !cancellationToken.IsCancellationRequested);

    return children;
}

App Details

• Durable Functions extension version: v2.1.1:
• Azure Functions runtime version 2.0:

[f2bo]

So, should we just test for the end of the enumeration against "bnVsbA=="?

do
{
    var status = await client.GetStatusAsync(queryCondition, cancellationToken);
    ...
    queryCondition.ContinuationToken = status.ContinuationToken;
} while (queryCondition.ContinuationToken != "bnVsbA==");

If not, how do you use this API? The documentation does not mention this, or at least, I can't find it in either of these two pages.

https://docs.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-instance-management

https://docs.microsoft.com/en-us/dotnet/api/microsoft.azure.webjobs.extensions.durabletask.idurableorchestrationclient.getstatusasync?view=azure-dotnet#Microsoft_Azure_WebJobs_Extensions_DurableTask_IDurableOrchestrationClient_GetStatusAsync_Microsoft_Azure_WebJobs_Extensions_DurableTask_OrchestrationStatusQueryCondition_System_Threading_CancellationToken_

[cgillum]

Hi @f2bo yeah, this looks pretty broken. I think your workaround for now is okay, but this definitely needs to be fixed. Thanks for raising the issue and providing a repro.

[f2bo]

Thanks @cgillum.

Just to be safe, the fix will be to return null instead, correct? So, once the bug is fixed, we'll still be fine if we check this as:

while (queryCondition.ContinuationToken != null && queryCondition.ContinuationToken != "bnVsbA==");

[cgillum]

Yes, this is definitely a good idea.

[ConnorMcMahon]

PR to handle this here: Azure/durabletask#372

[ConnorMcMahon]

Fixed in 2.2.0