Why Does Polly Retry Policy Not Retry on HttpClient.Timeout Exceptions?

The behavior you’re seeing is because HttpClient’s built‑in timeout “cancels” the request by triggering a TaskCanceledException internally—and that exception, even though you’ve configured your policy to handle TaskCanceledException, gets raised by HttpClient’s cancellation mechanism. This means the timeout is happening outside the scope where Polly can cleanly retry the request.

In other words, when the HttpClient.Timeout elapses, HttpClient cancels the request and throws an exception that isn’t “retryable” in the way you expect. This is compounded if the endpoint is rate limiting your requests. Even if you increase the HttpClient.Timeout, if the remote endpoint is causing delays (or there’s additional network throttling) then the same cancellation happens.

A common workaround is to disable the HttpClient’s built‑in timeout by setting it to Timeout.InfiniteTimeSpan and instead use an external cancellation mechanism (for example, by using Polly’s TimeoutPolicy or by attaching your own CancellationToken with CancelAfter). That way the entire timeout is under your control and Polly can intercept, catch, and retry the TaskCanceledException as needed.

Here’s an example of that approach:

CSHARPCopied
// Set HttpClient's timeout to infinite so that our Polly policies can control cancellation.
_httpClient = new HttpClient(_httpClientHandler) 
{ 
    Timeout = Timeout.InfiniteTimeSpan 
};

// Define a timeout policy that cancels the operation if it takes too long.
var timeoutPolicy = Policy.TimeoutAsync<HttpResponseMessage>(TimeSpan.FromSeconds(10));

// Define the retry policy with exponential backoff.
var retryPolicy = Policy<HttpResponseMessage>
    .Handle<HttpRequestException>()
    .Or<TaskCanceledException>()
    .OrResult(r => !r.IsSuccessStatusCode)
    .WaitAndRetryForeverAsync(
        retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)),
        onRetry: (outcome, retryCount, timeSpan) =>
        {
            _logger.Log(LogEnums.Error, $"Attempt {retryCount} failed. Retrying in {timeSpan.TotalSeconds} seconds...");
        });

// Combine the timeout and retry policies.
var policyWrap = Policy.WrapAsync(retryPolicy, timeoutPolicy);

var stringPayload = JsonConvert.SerializeObject(new { key = "days", options = date.ToString("yyyy-MM-dd") });
var httpContent = new StringContent(stringPayload, Encoding.UTF8, "application/json");

var response = await policyWrap.ExecuteAsync(() =>
    _httpClient.PostAsync($"{_moduleConfig.Endpoint}/options/selected", httpContent));

By managing the timeout externally, Polly gets full control over cancellations and can successfully retry the operation when it times out.