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The previous installment of this blog series on .NET 8.0 is AddStandardResilienceHandler() Introduced. This post is about customizing the default settings.

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alternative to AddStandardResilienceHandler() You can do it through AddResilienceHandler() Define your own Polly pipeline. Figure 1 shows the standard pipeline.

The following self-defined pipeline uses only orders 2 through 5 from the above table with the following settings:

• Total request timeout: 10 seconds
• Repeat: The call is repeated up to five times. The interval between trials is a constant 1 second. A screen is output when the trial is completed.
• Circuit breaker: abort if 50% of requests fail in 10 seconds, but as soon as possible after 5 requests
• Attempt timeout: 2 seconds

services.AddHttpClient(
  // Timeout insgesamt: Hier 10 Sekunden
  client => { client.Timeout = new TimeSpan(0,0,10); })
  .AddResilienceHandler(
   "CustomPipeline",
   static builder =>
   {
   // Wiederholungen bei Fehlern
   // Hier: Der Aufruf wird bis zu fünf Mal wiederholt. Der Abstand zwischen den Versuchen ist konstant 1 Sekunde. Bei dem Versuch gibt es eine Bildschirmausgabe.
   // https://www.pollydocs.org/strategies/retry.html
   builder.AddRetry(new HttpRetryStrategyOptions
    {
     // Customize and configure the retry logic.
     BackoffType = DelayBackoffType.Constant, // oder Linear oder Exponential
     Delay = TimeSpan.FromSeconds(1),
     MaxRetryAttempts = 10,
 
     OnRetry = static (args) =>
     {
      CUI.Cyan($"{DateTime.Now.ToLongTimeString()} Versuch #{args.AttemptNumber} Zeit seit letztem Versuch:{(int)(DateTime.Now - lastTry).TotalMilliseconds} ms Dauer:{args.Duration} Grund:{args.Outcome.Result} \n");
      lastTry = DateTime.Now;
      return ValueTask.CompletedTask;
     },
    });
 
    // Trennschalter, wenn zu viele Fehler passieren
    // Hier: Abbruch wenn in 10 Sekunden 50% der Anfragen fehlschlagen, frühestens aber nach 5 Anfragen
    // https://www.pollydocs.org/strategies/circuit-breaker.html
    builder.AddCircuitBreaker(new HttpCircuitBreakerStrategyOptions
    {
     // Customize and configure the circuit breaker logic.
     SamplingDuration = TimeSpan.FromSeconds(10),
     FailureRatio = 0.5,
     MinimumThroughput = 5,
     ShouldHandle = static args =>
     {
      return ValueTask.FromResult(args is
      {
       Outcome.Result.StatusCode: HttpStatusCode.RequestTimeout or HttpStatusCode.TooManyRequests or HttpStatusCode.InternalServerError
      });
     }
    });
 
    // Timeout für einzelne Versuche
    // hier: 2 Sekunden
    // https://www.pollydocs.org/strategies/timeout.html
    builder.AddTimeout(TimeSpan.FromSeconds(2));
   });

(RME)