Set default max eager activities to 3 (#946)

Fixes #919

internal/internal_worker.go

@@ -65,8 +65,9 @@ const (
 	// center. And the poll API latency is about 5ms. With 2 poller, we could achieve around 300~400 RPS.
 	defaultConcurrentPollRoutineSize = 2
 
-	defaultMaxConcurrentActivityExecutionSize = 1000   // Large concurrent activity execution size (1k)
-	defaultWorkerActivitiesPerSecond          = 100000 // Large activity executions/sec (unlimited)
+	defaultMaxConcurrentActivityExecutionSize      = 1000 // Large concurrent activity execution size (1k)
+	defaultMaxConcurrentEagerActivityExecutionSize = 3
+	defaultWorkerActivitiesPerSecond               = 100000 // Large activity executions/sec (unlimited)
 
 	defaultMaxConcurrentLocalActivityExecutionSize = 1000   // Large concurrent activity execution size (1k)
 	defaultWorkerLocalActivitiesPerSecond          = 100000 // Large activity executions/sec (unlimited)
@@ -1602,6 +1603,9 @@ func setWorkerOptionsDefaults(options *WorkerOptions) {
 	if options.MaxHeartbeatThrottleInterval == 0 {
 		options.MaxHeartbeatThrottleInterval = defaultMaxHeartbeatThrottleInterval
 	}
+	if options.MaxConcurrentEagerActivityExecutionSize == 0 {
+		options.MaxConcurrentEagerActivityExecutionSize = defaultMaxConcurrentEagerActivityExecutionSize
+	}
 }
 
 // setClientDefaults should be needed only in unit tests.

internal/worker.go

@@ -209,7 +209,8 @@ type (
 		// workflow task schedules 3 more, only the first 2 will request eager
 		// execution.
 		//
-		// The default of 0 means unlimited and therefore only bound by
+		// If unset/0, this defaults to 3. Users wanting effectively unlimited can
+		// set this to a high value. This is still bounded by
 		// MaxConcurrentActivityExecutionSize.
 		//
 		// See DisableEagerActivities for a description of eager activity execution.
@@ -256,8 +257,10 @@ func IsReplayNamespace(dn string) bool {
 
 // NewWorker creates an instance of worker for managing workflow and activity executions.
 // client   - client created with client.Dial() or client.NewLazyClient().
-// taskQueue - is the task queue name you use to identify your client worker, also
-//            identifies group of workflow and activity implementations that are hosted by a single worker process.
+// taskQueue - is the task queue name you use to identify your client worker,
+// also identifies group of workflow and activity implementations that are
+// hosted by a single worker process.
+//
 // options 	- configure any worker specific options.
 func NewWorker(
 	client Client,