Great Cancellation Spinoff: Using Cancellation Tokens with Async Enumerators by msalaman · Pull Request #1649 · microsoft/mcp

msalaman · 2026-02-04T22:29:13Z

What does this PR do?

Makes sure a cancellationToken is used whenever an Async Enumerator is traversed using the WithCancellation method. Updated New Command instructions to implement this practice in future generated code

GitHub issue number?

#1583

Pre-merge Checklist

…numerable scenario

vukelich · 2026-02-05T22:50:45Z

 **API Pattern Discovery:**
 - Study existing services (e.g., Sql, Postgres, Redis) to understand resource access patterns
 - Use resource collections correctly
   - ✅ Good: `.GetSqlServers().GetAsync(serverName)`


GetAsync here should be using the CancellationToken parameter or using .WithCancellation

vukelich · 2026-02-05T22:51:49Z

    .GetLatestVirtualMachineScaleSetRollingUpgradeAsync(cancellationToken);

 // ✅ Correct: VMSS instances
 var vms = vmssResource.Value.GetVirtualMachineScaleSetVms().GetAllAsync();


Missing use of Cancellationoken. Also, it's missing await on the result.

vukelich · 2026-02-05T22:53:06Z

 // ✅ Correct: VMSS instances
 var vms = vmssResource.Value.GetVirtualMachineScaleSetVms().GetAllAsync();

 // Pattern: Get{ResourceType}() returns collection, then .GetAsync() or .GetAllAsync()


Both GetAsync and GetAllAsync have CancellationToken arguments. This should be updated to reflect that. I think GetAsync typically takes a string argument for a resource name, so make sure your update includes that detail.

vukelich · 2026-02-05T22:54:10Z

        string subscription,
        string? resourceGroup = null,
        RetryPolicyOptions? retryPolicy = null,
        CancellationToken cancellationToken);


This should have an optional parameter. Probably a miss from a previous change I made.

vukelich · 2026-02-05T22:55:28Z

 - **Pattern**:
 ```csharp
 // Correct - use service
 var subscriptionResource = await _subscriptionService.GetSubscription(subscription, null, retryPolicy);


This line is missing using CancellationToken.

vukelich · 2026-02-05T22:56:37Z

 **Issue: `cannot convert from 'System.Threading.CancellationToken' to 'string'`**
 - **Cause**: Wrong parameter order in resource manager method calls
 - **Solution**: Check method signatures; many Azure SDK methods don't take CancellationToken as second parameter
 - **Fix**: Use `.GetAsync(resourceName)` instead of `.GetAsync(resourceName, cancellationToken)`


Please verify if this "issue" correct, and if the fix should also say to use .WithCancellation

vukelich · 2026-02-05T22:57:22Z


 **Issue: Wrong resource access pattern**
 - **Problem**: Using `.GetSqlServerAsync(name, cancellationToken)`
 - **Solution**: Use resource collections: `.GetSqlServers().GetAsync(name)`


Add .WithCancellation?

vukelich · 2026-02-05T22:58:37Z

        _storageService = storageService;
    }

    public override async Task<CommandResponse> ExecuteAsync(


I missed this in my earlier changes. ExecuteAsync has a CancellationToken argument and should be in this example. Also update the GetStorageAccountsAsync invocation as necessary to show using the CancellationToken

vukelich · 2026-02-05T22:59:38Z

        CancellationToken cancellationToken = default)
    {
        // ✅ Use base class methods that handle authentication and ARM client creation
        var armClient = await CreateArmClientAsync(tenant: null, retryPolicy);


CreateArmClientAsync takes a CancellationToken

vukelich · 2026-02-05T23:00:07Z

        _sqlService = sqlService;
    }

    public override async Task<CommandResponse> ExecuteAsync(


ExecuteAsync takes a CancellationToken

vukelich · 2026-02-05T23:00:23Z

        var options = BindOptions(parseResult);

        // ✅ Service calls are async and don't store request state
        var databases = await _sqlService.ListDatabasesAsync(


Forward CancellationToken parameter from ExecuteAsync signature.

vukelich · 2026-02-05T23:01:09Z


 ### Azure SDK Integration
 - [ ] All Azure SDK property names verified and correct
 - [ ] Resource access patterns use collections (e.g., `.GetSqlServers().GetAsync()`)


Make sure this includes something about CancellationToken

Potentially refer to the specific section headers with details?

vukelich · 2026-02-05T23:04:13Z

        try
        {
            // Perform a lightweight operation to validate the client
            await client.ReadAccountAsync();


Follow up item: ReadAccountAsync doesn't have a signature for a CancellationToken. We'll need to use a pattern that allows us to bail out if the cancellationToken is cancelled even if the underlying operation can't be aborted.

vukelich · 2026-02-05T23:08:16Z

        try
        {
            // Get all cached client keys
            keys = await _cacheService.GetGroupKeysAsync(CacheGroup, CancellationToken.None);


Please create a follow up work item to make sure we remove uses of CancellationToken.None, like this line. It'll be hard somewhere like here, but we can look online to see if there are recommendations. It's possible that we just don't await if we definitively know this is happening during application exiting. For example, we might be able to DI IHostApplicationLifetime and look at it the CancellationTokens attached to it.

vukelich · 2026-02-05T23:11:16Z

        {
            try
            {
                var client = await _cacheService.GetAsync<CosmosClient>(CacheGroup, key);


Similar as above. We might want to investigate if we should actually await on this. I'd recommend looking online for patterns about how to handle IAsyncDisposable, deciding if we care or how we write this code (which will likely vary based on the object's DI service lifetime, e.g., singleton, scoped, transient). I don't know the best pattern off the top of my head.

vukelich · 2026-02-05T23:18:03Z

        try
        {
            // Create ArmClient for deployments
            ArmClient armClient = await CreateArmClientWithApiVersionAsync("Microsoft.CognitiveServices/accounts/deployments", "2025-06-01", null, retryPolicy);


Missing CancellationToken.

Looks like CreateArmClientWithApiVersionAsync needs to add a parameter for it.

vukelich · 2026-02-05T23:19:43Z

                }
            };

            var result = await CreateOrUpdateGenericResourceAsync<Models.CognitiveServicesAccountDeploymentData>(


CreateOrUpdateGenericResourceAsync needs to add a CancellationToken parameter, and this invocation needs to pass one along.

vukelich · 2026-02-05T23:25:14Z

        var credential = await GetCredential(tenant, cancellationToken);
        var loadTestClient = new LoadTestRunClient(new Uri($"https://{dataPlaneUri}"), credential, CreateLoadTestingClientOptions(retryPolicy));

        var loadTestRunResponse = await loadTestClient.GetTestRunAsync(testRunId);


Lacks a way to be cancelled. Look into some sort of wrapping. Also, with stuff like this that are lacking CancellationToken within Azure SDK libraries, please file issues for the SDK to add them to methods that lack CancellationToken. File separate issues per resource provider for easier tracking and distribution of work by relevant owners.

Actually, for GetTestRunAsync, it has a parameter RequestContext which has a CancellationToken property. Should we use that? If so, are there other Azure SDK methods that lack CancellationToken as explicit method parameters but do honor a RequestContext.CancellationToken? You might want to chat with someone on the .NET Azure SDK to confirm if we should depend on RequestContext.

vukelich · 2026-02-05T23:28:44Z


        using var requestContent = RequestContent.Create(JsonSerializer.Serialize(requestBody, LoadTestJsonContext.Default.TestRunRequest));

        var loadTestRunResponse = await loadTestClient.BeginTestRunAsync(


Missing CancellationToken. As with other LoadTestingService.cs comment of mine, should we use the RequestContext parameter with an assigned CancellationToken?

vukelich · 2026-02-05T23:29:11Z

        var credential = await GetCredential(tenant, cancellationToken);
        var loadTestClient = new LoadTestAdministrationClient(new Uri($"https://{dataPlaneUri}"), credential, CreateLoadTestingClientOptions(retryPolicy));

        var loadTestResponse = await loadTestClient.GetTestAsync(testId);


Missing CancellationToken. As with other LoadTestingService.cs comment of mine, should we use the RequestContext parameter with an assigned CancellationToken?

vukelich · 2026-02-05T23:29:49Z

            }
        };

        var loadTestResponse = await loadTestClient.CreateOrUpdateTestAsync(testId, RequestContent.Create(JsonSerializer.Serialize(testRequestPayload, LoadTestJsonContext.Default.TestRequestPayload)));


Missing CancellationToken. As with other LoadTestingService.cs comment of mine, should we use the RequestContext parameter with an assigned CancellationToken?

vukelich · 2026-02-05T23:32:30Z

@@ -103,7 +103,7 @@ public override async Task<List<string>> GetAvailableRegionsAsync(string resourc
            {
                var quotas = subscription.GetModelsAsync(region);


Missing use of CancellationToken parameter.

Even though it's done in the await foreach, I think we should always make sure to use CancellationToken parameters where available.

vukelich · 2026-02-05T23:36:41Z

@@ -153,7 +153,7 @@ public override async Task<List<string>> GetAvailableRegionsAsync(string resourc
            try
            {
                AsyncPageable<PostgreSqlFlexibleServerCapabilityProperties> result = subscription.ExecuteLocationBasedCapabilitiesAsync(region);


Also has a CancellationToken parameter.

…erators (microsoft#1649) * add cancellation token usage to enumerator scenarios * update new command instructions to use cancellation token for async enumerable scenario

msalaman added 2 commits February 4, 2026 15:37

add cancellation token usage to enumerator scenarios

90bd4a7

update new command instructions to use cancellation token for async e…

9ee3788

…numerable scenario

github-project-automation Bot added this to Azure MCP Server Feb 4, 2026

github-project-automation Bot moved this to Untriaged in Azure MCP Server Feb 4, 2026

github-actions Bot added tools-CosmosDB tools-FileShares tools-Foundry Azure AI Foundry tools-FunctionApp tools-LoadTesting tools-Redis tools-Search Search tools-SignalR Azure SignalR tools-StorageSync labels Feb 4, 2026

msalaman marked this pull request as ready for review February 4, 2026 22:30

msalaman requested a review from JialinXin as a code owner February 4, 2026 22:30

Copilot AI review requested due to automatic review settings February 4, 2026 22:30

msalaman requested review from a team, HaofanLiao, ankushbindlish2, jongio, kszobi, pablocastro, philon-msft, qianwens, sharedferret and xiangyan99 as code owners February 4, 2026 22:30

msalaman requested review from JonathanCrd, conniey and wbreza February 4, 2026 22:30

alzimmermsft approved these changes Feb 5, 2026

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github-project-automation Bot moved this from Untriaged to In Progress in Azure MCP Server Feb 5, 2026

msalaman merged commit d6c9ee1 into main Feb 5, 2026
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msalaman deleted the masalama/cancellationTokensForEnumerators branch February 5, 2026 20:12

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vukelich reviewed Feb 5, 2026

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msalaman mentioned this pull request Feb 10, 2026

[Remote] Great cancellation - pending work on non-interfaces #1583

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		using var requestContent = RequestContent.Create(JsonSerializer.Serialize(requestBody, LoadTestJsonContext.Default.TestRunRequest));

		var loadTestRunResponse = await loadTestClient.BeginTestRunAsync(

		@@ -103,7 +103,7 @@ public override async Task<List<string>> GetAvailableRegionsAsync(string resourc
		{
		var quotas = subscription.GetModelsAsync(region);

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msalaman commented Feb 4, 2026

What does this PR do?

GitHub issue number?

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