Clearing history while debugging azure durable functions

Question

Durable functions keep a state in storage, this is what makes them work, but it is very troublesome while debugging and developing. I have a large number of runs which have not completed and that the system tries to run again when I start the process. Some of the runs have erroneous data same which causes exceptions while others have been terminated early as something did not work as expected.

I don't want to run all the old cases when starting my application in debug (running against my local storage account). How can I automatically clear all data so only new functions will trigger?

Answer 1

You can use Azure Core Tools to purge the orchestration instance state.

First you need to make sure that the Azure Core Tools is installed for your particular Azure Function version. You can do this using the NPM package manager. (Note that this is for the Azure Functions Version - V3.)

npm install -g azure-functions-core-tools@3

Then open a command prompt in the root directory of your Azure Functions project. The Azure Core Tools requires the host.json file from your project to identify your orchestration instances.

You can use the following to look at all of the available actions:

func durable 

You can then purge the instance history using the following:

func durable purge-history

Answer 2

You may call the PurgeInstanceHistoryAsync method with one of the following:

1. An orchestration instance ID

[FunctionName("PurgeInstanceHistory")]
public static Task Run(
    [DurableClient] IDurableOrchestrationClient client,
    [ManualTrigger] string instanceId)
{
    return client.PurgeInstanceHistoryAsync(instanceId);
}

2. Time interval

[FunctionName("PurgeInstanceHistory")]
public static Task Run(
    [DurableClient] IDurableOrchestrationClient client,
    [TimerTrigger("0 0 12 * * *")]TimerInfo myTimer)
{
    return client.PurgeInstanceHistoryAsync(
        DateTime.MinValue,
        DateTime.UtcNow.AddDays(-30),  
        new List<OrchestrationStatus>
        {
            OrchestrationStatus.Completed
        });
}

Reference for code snippets above: https://learn.microsoft.com/en-gb/azure/azure-functions/durable/durable-functions-instance-management#purge-instance-history

Answer 3

For everyone else wondering just how on earth to do this.

1. Install the Microsoft Azure Storage Explorer
2. Add a connection to azure storage, but choose Local storage emulator

4. Use the defaults / click next.

At this point, Click on Local & Attached in the Explorer. Click on (Emulator Default Ports) (Key) -> Tables. Delete the task hug history table, and relaunch your application.

From this point, its only a matter of dev time to figure out a way to do it programatically.

Answer 4

There is now this VsCode extension, which now also has 'Purge Durable Functions History' feature. Type 'Purge Durable Functions History' in your Command Palette - and there you go. If you're not using VsCode, then the same tool is available as a standalone service, that you can either run locally or deploy into Azure.