Merge pull request danielgerlag#287 from eddie3716/master

WorkflowOptions support for configuring max number of concurrent tasks.

Author: danielgerlag

src/WorkflowCore/Models/WorkflowOptions.cs

@@ -8,6 +8,8 @@ namespace WorkflowCore.Models
 {
     public class WorkflowOptions
     {
+        internal static readonly int MinimumNumberOfConcurrentWorkflows = 2;
+
         internal Func<IServiceProvider, IPersistenceProvider> PersistanceFactory;
         internal Func<IServiceProvider, IQueueProvider> QueueFactory;
         internal Func<IServiceProvider, IDistributedLockProvider> LockFactory;
@@ -16,6 +18,7 @@ public class WorkflowOptions
         internal TimeSpan PollInterval;
         internal TimeSpan IdleTime;
         internal TimeSpan ErrorRetryInterval;
+        internal int? MaxConcurrentWorkflows;
 
         public IServiceCollection Services { get; private set; }
 
@@ -67,6 +70,16 @@ public void UseErrorRetryInterval(TimeSpan interval)
         {
             ErrorRetryInterval = interval;
         }
+
+        public void UseMaxConcurrentWorkflows(int? maxConcurrentWorkflows)
+        {
+            if (maxConcurrentWorkflows.HasValue && maxConcurrentWorkflows.Value < MinimumNumberOfConcurrentWorkflows)
+            {
+                throw new ArgumentOutOfRangeException($"If {nameof(maxConcurrentWorkflows)} is specified, it cannot be less than ${MinimumNumberOfConcurrentWorkflows}.");
+            }
+
+            MaxConcurrentWorkflows = maxConcurrentWorkflows;
+        }
     }
 
 }

src/WorkflowCore/Services/BackgroundTasks/WorkflowConsumer.cs

@@ -15,6 +15,8 @@ internal class WorkflowConsumer : QueueConsumer, IBackgroundTask
         private readonly ObjectPool<IPersistenceProvider> _persistenceStorePool;
         private readonly ObjectPool<IWorkflowExecutor> _executorPool;
 
+        protected override int MaxConcurrentItems => Options.MaxConcurrentWorkflows ?? base.MaxConcurrentItems;
+
         protected override QueueType Queue => QueueType.Workflow;
 
         public WorkflowConsumer(IPooledObjectPolicy<IPersistenceProvider> persistencePoolPolicy, IQueueProvider queueProvider, ILoggerFactory loggerFactory, IServiceProvider serviceProvider, IWorkflowRegistry registry, IDistributedLockProvider lockProvider, IPooledObjectPolicy<IWorkflowExecutor> executorPoolPolicy, IDateTimeProvider datetimeProvider, WorkflowOptions options)