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durable-task-sub-orchestrations.md

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author hhunter-ms
title Sub-orchestrations - Azure
description Learn how to call orchestrations from orchestrations in Durable Functions and Durable Task SDKs.
ms.topic concept-article
ms.service durable-task
ms.date 02/25/2026
ms.author azfuncdf
zone_pivot_groups azure-durable-approach

Sub-orchestrations

In addition to calling activity functions, orchestrator functions can call other orchestrator functions. For example, you can build a larger orchestration out of a library of smaller orchestrator functions. Or you can run multiple instances of an orchestrator function in parallel.

An orchestrator function calls another orchestrator function using the call-sub-orchestrator API. For more information on automatic retry, see Error Handling & Compensation.

Sub-orchestrator functions behave just like activity functions from the caller's perspective. They can return a value, and the parent orchestrator function catches any exception they throw.

::: zone pivot="durable-functions"

Note

In PowerShell, sub-orchestrations are supported only in the standalone SDK: AzureFunctions.PowerShell.Durable.SDK. For the differences between the standalone SDK and the legacy built-in SDK, see the migration guide.

::: zone-end

Example

The following example illustrates an IoT ("Internet of Things") scenario where multiple devices need to be set up. The following function represents the setup workflow that runs for each device:

::: zone pivot="durable-functions"

C#

Isolated worker model 
public static async Task DeviceProvisioningOrchestration(
    [OrchestrationTrigger] TaskOrchestrationContext context, string deviceId)
{
    // Step 1: Create an installation package in blob storage and return a SAS URL.
    Uri sasUrl = await context.CallActivityAsync<Uri>("CreateInstallationPackage", deviceId);

    // Step 2: Notify the device that the installation package is ready.
    await context.CallActivityAsync("SendPackageUrlToDevice", (deviceId, sasUrl));

    // Step 3: Wait for the device to acknowledge that it has downloaded the new package.
    await context.WaitForExternalEvent<bool>("DownloadCompletedAck");

    // Step 4: ...
}

In-process model 
public static async Task DeviceProvisioningOrchestration(
    [OrchestrationTrigger] IDurableOrchestrationContext context)
{
    string deviceId = context.GetInput<string>();

    // Step 1: Create an installation package in blob storage and return a SAS URL.
    Uri sasUrl = await context.CallActivityAsync<Uri>("CreateInstallationPackage", deviceId);

    // Step 2: Notify the device that the installation package is ready.
    await context.CallActivityAsync("SendPackageUrlToDevice", Tuple.Create(deviceId, sasUrl));

    // Step 3: Wait for the device to acknowledge that it has downloaded the new package.
    await context.WaitForExternalEvent<bool>("DownloadCompletedAck");

    // Step 4: ...
}

JavaScript

const df = require("durable-functions");

df.app.orchestration("deviceProvisioningOrchestration", function* (context) {
    const deviceId = context.df.getInput();

    // Step 1: Create an installation package in blob storage and return a SAS URL.
    const sasUrl = yield context.df.callActivity("createInstallationPackage", deviceId);

    // Step 2: Notify the device that the installation package is ready.
    yield context.df.callActivity("sendPackageUrlToDevice", { id: deviceId, url: sasUrl });

    // Step 3: Wait for the device to acknowledge that it has downloaded the new package.
    yield context.df.waitForExternalEvent("downloadCompletedAck");

    // Step 4: ...
});

Python

import azure.functions as func
import azure.durable_functions as df

def orchestrator_function(context: df.DurableOrchestrationContext):
    device_id = context.get_input()

    # Step 1: Create an installation package in blob storage and return a SAS URL.
    sas_url = yield context.call_activity("CreateInstallationPackage", device_id)

    # Step 2: Notify the device that the installation package is ready.
    yield context.call_activity("SendPackageUrlToDevice", { "id": device_id, "url": sas_url })

    # Step 3: Wait for the device to acknowledge that it has downloaded the new package.
    yield context.call_activity("DownloadCompletedAck")

    # Step 4: ...

PowerShell

param($Context)

$deviceId = $Context.Input

# Step 1: Create an installation package in blob storage and return a SAS URL.
$sasUrl = Invoke-DurableActivity -FunctionName "CreateInstallationPackage" -Input $deviceId

# Step 2: Notify the device that the installation package is ready.
$deviceInfo = @{
    id = $deviceId
    url = $sasUrl
}
Invoke-DurableActivity -FunctionName "SendPackageUrlToDevice" -Input $deviceInfo

# Step 3: Wait for the device to acknowledge that it has downloaded the new package.
Start-DurableExternalEventListener -EventName "DownloadCompletedAck"

# Step 4: ...

Java

@FunctionName("DeviceProvisioningOrchestration")
public void deviceProvisioningOrchestration(
        @DurableOrchestrationTrigger(name = "ctx") TaskOrchestrationContext ctx) {
    // Step 1: Create an installation package in blob storage and return a SAS URL.
    String deviceId = ctx.getInput(String.class);
    String blobUri = ctx.callActivity("CreateInstallPackage", deviceId, String.class).await();

    // Step 2: Notify the device that the installation package is ready.
    String[] args = { deviceId, blobUri };
    ctx.callActivity("SendPackageUrlToDevice", args).await();

    // Step 3: Wait for the device to acknowledge that it has downloaded the new package.
    ctx.waitForExternalEvent("DownloadCompletedAck").await();

    // Step 4: ...
}

::: zone-end

::: zone pivot="durable-task-sdks"

C#

using Microsoft.DurableTask;

[DurableTask]
public class DeviceProvisioningOrchestration : TaskOrchestrator<string, object?>
{
    public override async Task<object?> RunAsync(TaskOrchestrationContext context, string deviceId)
    {
        // Step 1: Create an installation package in blob storage and return a SAS URL.
        Uri sasUrl = await context.CallActivityAsync<Uri>("CreateInstallationPackage", deviceId);

        // Step 2: Notify the device that the installation package is ready.
        await context.CallActivityAsync("SendPackageUrlToDevice", (deviceId, sasUrl.ToString()));

        // Step 3: Wait for the device to acknowledge that it has downloaded the new package.
        await context.WaitForExternalEvent<bool>("DownloadCompletedAck");

        // Step 4: ...
        return null;
    }
}

JavaScript

This sample is shown for .NET, Java, and Python.

Python

from durabletask import task

def device_provisioning_orchestrator(ctx: task.OrchestrationContext, device_id: str):
    # Step 1: Create an installation package in blob storage and return a SAS URL.
    sas_url = yield ctx.call_activity("create_installation_package", input=device_id)

    # Step 2: Notify the device that the installation package is ready.
    yield ctx.call_activity("send_package_url_to_device", input={"id": device_id, "url": sas_url})

    # Step 3: Wait for the device to acknowledge that it has downloaded the new package.
    yield ctx.wait_for_external_event("DownloadCompletedAck")

    # Step 4: ...

PowerShell

This sample is shown for .NET, Java, and Python.

Java

import com.microsoft.durabletask.TaskOrchestration;
import com.microsoft.durabletask.TaskOrchestrationContext;

public class DeviceProvisioningOrchestration implements TaskOrchestration {
    @Override
    public void run(TaskOrchestrationContext ctx) {
        String deviceId = ctx.getInput(String.class);

        // Step 1: Create an installation package in blob storage and return a SAS URL.
        String blobUri = ctx.callActivity("CreateInstallPackage", deviceId, String.class).await();

        // Step 2: Notify the device that the installation package is ready.
        String[] args = { deviceId, blobUri };
        ctx.callActivity("SendPackageUrlToDevice", args).await();

        // Step 3: Wait for the device to acknowledge that it has downloaded the new package.
        ctx.waitForExternalEvent("DownloadCompletedAck").await();

        // Step 4: ...
    }
}

::: zone-end

This orchestrator function can be used as-is for one-off device setup, or it can be part of a larger orchestration. In the latter case, the parent orchestrator function schedules instances of DeviceProvisioningOrchestration by using the "call-sub-orchestrator" API.

The following example shows how to run multiple orchestrator functions in parallel.

::: zone pivot="durable-functions"

C#

Isolated worker model 
[Function("ProvisionNewDevices")]
public static async Task ProvisionNewDevices(
    [OrchestrationTrigger] TaskOrchestrationContext context)
{
    string[] deviceIds = await context.CallActivityAsync<string[]>("GetNewDeviceIds");

    // Run multiple device provisioning flows in parallel
    var provisioningTasks = new List<Task>();
    foreach (string deviceId in deviceIds)
    {
        Task provisionTask = context.CallSubOrchestratorAsync("DeviceProvisioningOrchestration", deviceId);
        provisioningTasks.Add(provisionTask);
    }

    await Task.WhenAll(provisioningTasks);

    // ...
}

In-process model 
[FunctionName("ProvisionNewDevices")]
public static async Task ProvisionNewDevices(
    [OrchestrationTrigger] IDurableOrchestrationContext context)
{
    string[] deviceIds = await context.CallActivityAsync<string[]>("GetNewDeviceIds");

    // Run multiple device provisioning flows in parallel
    var provisioningTasks = new List<Task>();
    foreach (string deviceId in deviceIds)
    {
        Task provisionTask = context.CallSubOrchestratorAsync("DeviceProvisioningOrchestration", deviceId);
        provisioningTasks.Add(provisionTask);
    }

    await Task.WhenAll(provisioningTasks);

    // ...
}

JavaScript

const df = require("durable-functions");

df.app.orchestration("provisionNewDevices", function* (context) {
    const deviceIds = yield context.df.callActivity("getNewDeviceIds");

    // Run multiple device provisioning flows in parallel
    const provisioningTasks = [];
    var id = 0;
    for (const deviceId of deviceIds) {
        const child_id = context.df.instanceId + `:${id}`;
        const provisionTask = context.df.callSubOrchestrator(
            "deviceProvisioningOrchestration",
            deviceId,
            child_id
        );
        provisioningTasks.push(provisionTask);
        id++;
    }

    yield context.df.Task.all(provisioningTasks);

    // ...
});

Python

import azure.functions as func
import azure.durable_functions as df

def orchestrator_function(context: df.DurableOrchestrationContext):

    device_IDs = yield context.call_activity("GetNewDeviceIds")

    # Run multiple device provisioning flows in parallel
    provisioning_tasks = []
    id_ = 0
    for device_id in device_IDs:
        child_id = f"{context.instance_id}:{id_}"
        provision_task = context.call_sub_orchestrator("DeviceProvisioningOrchestration", device_id, child_id)
        provisioning_tasks.append(provision_task)
        id_ += 1

    yield context.task_all(provisioning_tasks)

    # ...

PowerShell

param($Context)

$deviceIds = Invoke-DurableActivity -FunctionName "GetNewDeviceIds"

# Run multiple device setting up flows in parallel
$provisioningTasks = @()
for ($i = 0; $i -lt $deviceIds.Count; $i++) {
    $deviceId = $deviceIds[$i]
    $childId = "$($Context.InstanceId):$i"
    $provisionTask = Invoke-DurableSubOrchestrator `
        -FunctionName "DeviceProvisioningOrchestration" `
        -Input $deviceId `
        -InstanceId $childId `
        -NoWait
    $provisioningTasks += $provisionTask
}

Wait-DurableTask -Task $provisioningTasks

# ...

Java

@FunctionName("ProvisionNewDevices")
public void provisionNewDevices(
        @DurableOrchestrationTrigger(name = "ctx") TaskOrchestrationContext ctx) {
    List<?> deviceIDs = ctx.getInput(List.class);

    // Schedule each device provisioning sub-orchestration to run in parallel
    List<Task<Void>> parallelTasks = deviceIDs.stream()
        .map(device -> ctx.callSubOrchestrator("DeviceProvisioningOrchestration", device))
        .collect(Collectors.toList());

    // ...
}

Note

Sub-orchestrations must be defined in the same function app as the parent orchestration. If you need to call and wait for orchestrations in another function app, consider using the built-in support for HTTP APIs and the HTTP 202 polling consumer pattern. For more information, see HTTP features.

Next steps

[!div class="nextstepaction"] Learn how to set a custom orchestration status

::: zone-end

::: zone pivot="durable-task-sdks"

C#

using Microsoft.DurableTask;

[DurableTask]
public class ProvisionNewDevices : TaskOrchestrator<object?, object?>
{
    public override async Task<object?> RunAsync(TaskOrchestrationContext context, object? input)
    {
        string[] deviceIds = await context.CallActivityAsync<string[]>("GetNewDeviceIds");

        // Run multiple device provisioning flows in parallel
        var provisioningTasks = new List<Task>();
        foreach (string deviceId in deviceIds)
        {
            Task provisionTask = context.CallSubOrchestratorAsync("DeviceProvisioningOrchestration", deviceId);
            provisioningTasks.Add(provisionTask);
        }

        await Task.WhenAll(provisioningTasks);
        return null;
    }
}

JavaScript

This sample is shown for .NET, Java, and Python.

Python

from durabletask import task

def provision_new_devices(ctx: task.OrchestrationContext, _):
    device_ids = yield ctx.call_activity("get_new_device_ids")

    # Run multiple device provisioning flows in parallel
    provisioning_tasks = []
    for device_id in device_ids:
        provision_task = ctx.call_sub_orchestrator(device_provisioning_orchestrator, input=device_id)
        provisioning_tasks.append(provision_task)

    yield task.when_all(provisioning_tasks)

PowerShell

This sample is shown for .NET, Java, and Python.

Java

import com.microsoft.durabletask.TaskOrchestration;
import com.microsoft.durabletask.TaskOrchestrationContext;

public class ProvisionNewDevices implements TaskOrchestration {
    @Override
    public void run(TaskOrchestrationContext ctx) {
        List<?> deviceIDs = ctx.getInput(List.class);

        // Schedule each device provisioning sub-orchestration to run in parallel
        List<Task<Void>> parallelTasks = deviceIDs.stream()
            .map(device -> ctx.callSubOrchestrator("DeviceProvisioningOrchestration", device))
            .collect(Collectors.toList());

        ctx.allOf(parallelTasks).await();
    }
}

Next steps

[!div class="nextstepaction"] Get started with Durable Task SDKs

::: zone-end