How can I get the last result from a retrystrategy in an outer timeout strategy using Polly?

Question

I have the following requirement that I can't really figure out how to solve.

Using Polly in C#/.NET: Given an user defined timeout and an internally/system defined retry strategy. How can I get the result from the latest retry attempt when the timeout is expired?

I have come up with this solution, but it seems odd that I have to capture the result like in the following code. If I do not have the timeout + fallback strategy ExecuteAsyc will return the latest attempt by itself.

var pipelineBuilder = new ResiliencePipelineBuilder<(Orders.Contracts.OrderView?, RequestResult)>();

(Orders.Contracts.OrderView?, RequestResult) outerTempResult = new(null, new()); // A non-empty temp result for fallbacks.

var pipeline = pipelineBuilder
    .AddFallback(new()
    {
        ShouldHandle = new PredicateBuilder<(Orders.Contracts.OrderView?, RequestResult)>().Handle<TimeoutRejectedException>(),
        FallbackAction = args => Outcome.FromResultAsValueTask(outerTempResult),
    })
    .AddTimeout(TimeSpan.FromMilliseconds(options.MaxPollingTimeout)) // Global timeout for the entire pipeline
    .AddRetry(new RetryStrategyOptions<(Orders.Contracts.OrderView?, RequestResult)>
    {
        ShouldHandle = new PredicateBuilder<(Orders.Contracts.OrderView?, RequestResult)>()
                .HandleResult(newOrder =>  newOrder.Item1 == null || newOrder.Item1.Status == S4.Orders.Contracts.OrderStatus.InProgress),
        Delay = TimeSpan.FromMilliseconds(OrderSettings.RetryInterval),
        MaxRetryAttempts = OrderSettings.RetryCount,
        BackoffType = DelayBackoffType.Linear,
        UseJitter = true,
        OnRetry = (args) =>
        {
            outerTempResult = args.Outcome.Result; // Assign this to an outer variable to use in the fallback handling callback.
            return ValueTask.CompletedTask;
        }
    })
.Build();

And the request execution looks like this:

var orderView = await pipeline.ExecuteAsync(async token =>
{
    return await this.orderServiceClient.GetOrderAsync(id);
}, CancellationToken.None);

return orderView.Item2.ToApiResult();

There is probably something obvious I am missing here...

Peter Csala · Accepted Answer · 2025-06-24 06:58:17Z

1

Gladly you don't need outerTempResult. You can use ResilienceContext to pass information between strategies, like this:

var context_key = new ResiliencePropertyKey<(Orders.Contracts.OrderView?, RequestResult)>("LastResult");

var pipeline = new ResiliencePipelineBuilder<(Orders.Contracts.OrderView?, RequestResult)>()
    .AddFallback(new()
    {
        ShouldHandle = ...,
        FallbackAction = args => 
        {
            var lastResult = args.Context.Properties.GetValue(context_key, fallback_value);
            return Outcome.FromResultAsValueTask(lastResult);
        },
    })
    .AddTimeout(...)
    .AddRetry(new RetryStrategyOptions<(Orders.Contracts.OrderView?, RequestResult)>
    {
        ShouldHandle = ...,
        OnRetry = args =>
        {
            args.Context.Properties.Set(context_key, args.Outcome.Result);
            return ValueTask.CompletedTask;
        }
    })
    .Build();

You can find here further information about the context.

edited Jun 24 at 6:58

answered Jun 12 at 11:33

Peter Csala

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2 Comments

Esben Bach Jun 24 at 5:22

I had to modify the above just a tiny bit, so that instead of Context.SetValue and Context.GetValue it becomes: For setting:

var key = new ResiliencePropertyKey<(Orders.Contracts.OrderView?, RequestResult)>("LastResult");  args.Context.Properties.Set(key, args.Outcome.Result);

For getting:

var key = new ResiliencePropertyKey<(Orders.Contracts.OrderView?, RequestResult)>("LastResult");  var lastResult = args.Context.Properties.GetValue(key, (null, new RequestResult()));

Other than that it works :) Thanks.

Peter Csala Jun 24 at 6:52

@EsbenBach Yes, you should use ResiliencePropertyKey not just a simple string. Sorry for the inconvience, I was putting together the example without probing it... I've updated the example code.

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