Add versioning samples/docs

Author: andystaples

docs/features.md

@@ -4,7 +4,11 @@ The following features are currently supported:
 
 ### Orchestrations
 
-Orchestrations are implemented using ordinary Python functions that take an `OrchestrationContext` as their first parameter. The `OrchestrationContext` provides APIs for starting child orchestrations, scheduling activities, and waiting for external events, among other things. Orchestrations are fault-tolerant and durable, meaning that they can automatically recover from failures and rebuild their local execution state. Orchestrator functions must be deterministic, meaning that they must always produce the same output given the same input.
+Orchestrators are implemented using ordinary Python functions that take an `OrchestrationContext` as their first parameter. The `OrchestrationContext` provides APIs for starting child orchestrations, scheduling activities, and waiting for external events, among other things. Orchestrations are fault-tolerant and durable, meaning that they can automatically recover from failures and rebuild their local execution state. Orchestrator functions must be deterministic, meaning that they must always produce the same output given the same input.
+
+#### Orchestration versioning
+
+Orchestrations may be assigned a version when they are first created. If an orchestration is given a version, it will continually be checked during its lifecycle to ensure that it remains compatible with the underlying orchestrator code. If the orchestrator code is updated while an orchestration is running, rules can be set that will define the behavior - whether the orchestration should fail, abandon for reprocessing at a later time, or attempt to run anyway. For more information, see [Orchestration versioning in Durable Functions](https://learn.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-orchestration-versioning) (Note that concepts specific to Azure Functions, such as host.json settings, do not apply) and [The provided examples](./supported-patterns.md)
 
 ### Activities
 

docs/supported-patterns.md

@@ -20,7 +20,7 @@ def sequence(ctx: task.OrchestrationContext, _):
     return [result1, result2, result3]
 ```
 
-You can find the full sample [here](../examples/activity_sequence.py).
+Link to the full [function chaining example](../examples/activity_sequence.py).
 
 ### Fan-out/fan-in
 
@@ -48,7 +48,7 @@ def orchestrator(ctx: task.OrchestrationContext, _):
     return {'work_items': work_items, 'results': results, 'total': sum(results)}
 ```
 
-You can find the full sample [here](../examples/fanout_fanin.py).
+Link to the full [fan-out sample](../examples/fanout_fanin.py).
 
 ### Human interaction and durable timers
 
@@ -79,4 +79,43 @@ def purchase_order_workflow(ctx: task.OrchestrationContext, order: Order):
 
 As an aside, you'll also notice that the example orchestration above works with custom business objects. Support for custom business objects includes support for custom classes, custom data classes, and named tuples. Serialization and deserialization of these objects is handled automatically by the SDK.
 
-You can find the full sample [here](../examples/human_interaction.py).
+Link to the full [human interaction sample](../examples/human_interaction.py).
+
+### Version-aware orchestrator
+
+When utilizing orchestration versioning, it is possible for an orchestrator to remain backwards-compatible with orchestrations created using the previously defined version. For instance, consider an orchestration defined with the following signature:
+
+```python
+def my_orchestrator(ctx: task.OrchestrationContext, order: Order):
+    """Dummy orchestrator function illustrating old logic"""
+    yield ctx.call_activity(activity_one)
+    yield ctx.call_activity(activity_two) 
+    return "Success"
+```
+
+Assume that any orchestrations created using this orchestrator were versioned 1.0.0. If the signature of this method needs to be updated to call activity_three between the calls to activity_one and activity_two, ordinarily this would break any running orchestrations at the time of deployment. However, the following orchestrator will be able to process both orchestraions versioned 1.0.0 and 2.0.0 after the change:
+
+```python
+def my_orchestrator(ctx: task.OrchestrationContext, order: Order):
+    """Version-aware dummy orchestrator capable of processing both old and new orchestrations"""
+    yield ctx.call_activity(activity_one)
+    if ctx.version > '1.0.0':
+        yield ctx.call_activity(activity_three)
+    yield ctx.call_activity(activity_two) 
+```
+
+Alternatively, if the orchestrator changes completely, the following syntax might be preferred:
+
+```python
+def my_orchestrator(ctx: task.OrchestrationContext, order: Order):
+    if ctx.version == '1.0.0':
+        yield ctx.call_activity(activity_one)
+        yield ctx.call_activity(activity_two)
+        return "Success
+    yield ctx.call_activity(activity_one)
+    yield ctx.call_activity(activity_three)
+    yield ctx.call_activity(activity_two) 
+    return "Success"        
+```
+
+Link to the full [version-aware orchestrator sample](../examples/version_aware_orchestrator.py)

examples/version_aware_orchestrator.py

@@ -0,0 +1,93 @@
+"""End-to-end sample that demonstrates how to configure an orchestrator
+that a dynamic number activity functions in parallel, waits for them all
+to complete, and prints an aggregate summary of the outputs."""
+import os
+import random
+
+from azure.identity import DefaultAzureCredential
+
+from durabletask import client, task, worker
+from durabletask.azuremanaged.client import DurableTaskSchedulerClient
+from durabletask.azuremanaged.worker import DurableTaskSchedulerWorker
+
+
+def activity_v1(ctx: task.ActivityContext, input: str) -> str:
+    """Activity function that returns a result for a given work item"""
+    print("processing input:", input)
+    return "Success from activity v1"
+
+
+def activity_v2(ctx: task.ActivityContext, input: str) -> str:
+    """Activity function that returns a result for a given work item"""
+    print("processing input:", input)
+    return "Success from activity v2"
+
+
+def orchestrator(ctx: task.OrchestrationContext, _):
+    """Orchestrator function that checks the orchestration version and has version-aware behavior
+    Use case: Updating an orchestrator with new logic while maintaining compatibility with previously
+    started orchestrations"""
+    if ctx.version == "1.0.0":
+        # For version 1.0.0, we use the original logic
+        result: int = yield ctx.call_activity(activity_v1, input="input for v1")
+    elif ctx.version == "2.0.0":
+        # For version 2.0.0, we use the updated logic
+        result: int = yield ctx.call_activity(activity_v2, input="input for v2")
+    else:
+        raise ValueError(f"Unsupported version: {ctx.version}")
+    return {
+        'result': result,
+    }
+
+
+# Use environment variables if provided, otherwise use default emulator values
+taskhub_name = os.getenv("TASKHUB", "default")
+endpoint = os.getenv("ENDPOINT", "http://localhost:8080")
+
+print(f"Using taskhub: {taskhub_name}")
+print(f"Using endpoint: {endpoint}")
+
+# Set credential to None for emulator, or DefaultAzureCredential for Azure
+credential = None if endpoint == "http://localhost:8080" else DefaultAzureCredential()
+
+# configure and start the worker - use secure_channel=False for emulator
+secure_channel = endpoint != "http://localhost:8080"
+with DurableTaskSchedulerWorker(host_address=endpoint, secure_channel=secure_channel,
+                                taskhub=taskhub_name, token_credential=credential) as w:
+    # This worker is versioned for v2, as the orchestrator code has already been updated
+    # CURRENT_OR_OLDER allows this worker to process orchestrations versioned below 2.0.0 - e.g. 1.0.0
+    w.use_versioning(worker.VersioningOptions(
+        version="2.0.0",
+        default_version="2.0.0",
+        match_strategy=worker.VersionMatchStrategy.CURRENT_OR_OLDER,
+        failure_strategy=worker.VersionFailureStrategy.FAIL
+    ))
+    w.add_orchestrator(orchestrator)
+    w.add_activity(activity_v1)
+    w.add_activity(activity_v2)
+    w.start()
+
+    # create a client, start an orchestration, and wait for it to finish
+    # The client's version matches the worker's version
+    c = DurableTaskSchedulerClient(host_address=endpoint, secure_channel=secure_channel,
+                                   taskhub=taskhub_name, token_credential=credential,
+                                   default_version="2.0.0")
+    # Schedule a new orchestration manually versioned to 1.0.0
+    # Normally, this would have been scheduled before the worker started from a worker also versioned v1.0.0,
+    # Here we are doing it manually to avoid creating two workers
+    instance_id_v1 = c.schedule_new_orchestration(orchestrator, version="1.0.0")
+    state_v1 = c.wait_for_orchestration_completion(instance_id_v1, timeout=30)
+    if state_v1 and state_v1.runtime_status == client.OrchestrationStatus.COMPLETED:
+        print(f'Orchestration v1 completed! Result: {state_v1.serialized_output}')
+    elif state_v1:
+        print(f'Orchestration v1 failed: {state_v1.failure_details}')
+
+    # Also check that the orchestrator can be run with the current version
+    instance_id = c.schedule_new_orchestration(orchestrator)
+    state = c.wait_for_orchestration_completion(instance_id, timeout=30)
+    if state and state.runtime_status == client.OrchestrationStatus.COMPLETED:
+        print(f'Orchestration completed! Result: {state.serialized_output}')
+    elif state:
+        print(f'Orchestration failed: {state.failure_details}')
+
+    exit()