Fix ordered consumer creation (#746)

* Fix ordered consumer creation

* Add exponential backoff with jitter for retries

Introduce `BackoffWithJitterAsync` to calculate delay with jitter, improving retry logic. Update `NatsJSOrderedConsumer` to utilize the new method during connection reset attempts.

Author: mtmk

src/NATS.Client.Core/NatsOpts.cs

@@ -4,6 +4,9 @@
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
 using NATS.Client.Core.Internal;
+#if NETSTANDARD
+using Random = NATS.Client.Core.Internal.NetStandardExtensions.Random;
+#endif
 
 namespace NATS.Client.Core;
 
@@ -186,3 +189,21 @@ internal NatsOpts ReadUserInfoFromConnectionString()
         }
     }
 }
+
+public static class NatsOptsExtensions
+{
+    /// <summary>
+    /// Applies an exponential backoff delay with an added random jitter for attempts.
+    /// </summary>
+    /// <param name="opts">The NatsOpts instance containing configuration settings for intervals and jitter.</param>
+    /// <param name="iter">The current attempt iteration, used to calculate the exponential delay.</param>
+    /// <returns>A task that completes after the calculated delay time has elapsed.</returns>
+    public static Task BackoffWithJitterAsync(this NatsOpts opts, int iter)
+    {
+        var baseDelay = opts.ReconnectWaitMin.TotalMilliseconds * Math.Pow(2, iter - 1);
+        var jitter = opts.ReconnectJitter.TotalMilliseconds * Random.Shared.NextDouble();
+
+        var delay = Math.Min(baseDelay + jitter, opts.ReconnectWaitMax.TotalMilliseconds);
+        return Task.Delay(TimeSpan.FromMilliseconds(delay));
+    }
+}

src/NATS.Client.JetStream/NatsJSOrderedConsumer.cs

@@ -2,6 +2,9 @@
 using Microsoft.Extensions.Logging;
 using NATS.Client.Core;
 using NATS.Client.JetStream.Models;
+#if NETSTANDARD
+using Random = NATS.Client.Core.Internal.NetStandardExtensions.Random;
+#endif
 
 namespace NATS.Client.JetStream;
 
@@ -314,11 +317,16 @@ private async Task<NatsJSConsumer> RecreateConsumer(string consumer, ulong seq,
             catch (NatsJSApiNoResponseException)
             {
             }
+            catch (NatsJSApiException apiException) when (apiException.Error.Code == 503)
+            {
+            }
 
             if (i == _opts.MaxResetAttempts)
             {
                 throw new NatsJSException("Maximum number of create attempts reached.");
             }
+
+            await _context.Connection.Opts.BackoffWithJitterAsync(i);
         }
 
         Info = info;