Add blog for batch future

Author: “Kevin”

blog/2025-09-15-introducing-batch-future-10x-faster-activity-execution.md

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+---
+title: "Introducing Batch Future: Controlled Concurrency for Activity Execution"
+description: "We're excited to announce Batch Future, a new feature in the Cadence Go client that provides controlled concurrency for bulk operations, preventing overwhelming downstream services while maintaining efficient parallel processing."
+date: 2025-09-19
+authors: kevinb
+tags:
+  - announcement
+  - performance
+  - releases
+---
+
+Are you struggling with uncontrolled concurrency when processing multiple activities? Do you find yourself hitting rate limits or overwhelming downstream services when running bulk operations? We've got great news for you!
+
+Today, we're thrilled to announce **Batch Future**—a powerful new feature in the Cadence Go client that provides controlled concurrency for bulk operations. You can now process multiple activities in parallel while maintaining precise control over how many run simultaneously.
+
+<!-- truncate -->
+
+## The Problem: Uncontrolled Concurrency
+
+Traditionally, when you need to process multiple items in a Cadence workflow, you'd write something like this:
+
+```go
+func ProcessUsers(ctx workflow.Context, userIDs []string) error {
+    var futures []workflow.Future
+    for _, userID := range userIDs {
+        future := workflow.ExecuteActivity(ctx, UpdateUserActivity, userID)
+        futures = append(futures, future)
+    }
+    
+    // Wait for all activities to complete
+    for _, future := range futures {
+        if err := future.Get(ctx, nil); err != nil {
+            return err
+        }
+    }
+    return nil
+}
+```
+
+This approach works, but it has **uncontrolled concurrency**:
+- All activities start simultaneously, potentially overwhelming downstream services
+- No way to limit concurrent executions
+- Difficult to manage resource usage
+- Can cause rate limiting or timeouts
+
+## The Solution: Batch Future
+
+With Batch Future, you can process users with **controlled concurrency**:
+
+```go
+func ProcessUsersBatch(ctx workflow.Context, userIDs []string, concurrency int) error {
+    // Create activity factories for each user
+    factories := make([]func(workflow.Context) workflow.Future, len(userIDs))
+    for i, userID := range userIDs {
+        userID := userID // Capture loop variable for closure
+        factories[i] = func(ctx workflow.Context) workflow.Future {
+            return workflow.ExecuteActivity(ctx, UpdateUserActivity, userID)
+        }
+    }
+    
+    // Execute with controlled concurrency
+    batch, err := workflow.NewBatchFuture(ctx, concurrency, factories)
+    if err != nil {
+        return fmt.Errorf("failed to create batch future: %w", err)
+    }
+    
+    // Wait for all activities to complete
+    return batch.Get(ctx, nil)
+}
+```
+
+## Key Benefits: Controlled Concurrency
+
+Batch Future provides several important advantages:
+
+- **Controlled Concurrency**: Limit simultaneous executions to prevent overwhelming downstream services
+- **Resource Management**: Better control over memory and CPU usage
+- **Rate Limiting Protection**: Avoid hitting API rate limits by controlling execution speed
+- **Graceful Cancellation**: All activities can be cancelled together if needed
+- **Simplified Error Handling**: Single point of failure handling for the entire batch
+
+## Real-World Use Cases
+
+Batch Future is perfect for scenarios like:
+
+### 1. Multi-Service Data Synchronization
+```go
+func SyncProductData(ctx workflow.Context, products []Product) error {
+    // Sync to multiple services with different concurrency limits
+    inventoryBatch := createBatch(ctx, products, 5, SyncToInventoryActivity)
+    searchBatch := createBatch(ctx, products, 3, SyncToSearchActivity)
+    analyticsBatch := createBatch(ctx, products, 2, SyncToAnalyticsActivity)
+    
+    // Wait for all sync operations to complete
+    if err := inventoryBatch.Get(ctx, nil); err != nil {
+        return fmt.Errorf("inventory sync failed: %w", err)
+    }
+    if err := searchBatch.Get(ctx, nil); err != nil {
+        return fmt.Errorf("search sync failed: %w", err)
+    }
+    return analyticsBatch.Get(ctx, nil)
+}
+
+func createBatch(ctx workflow.Context, items []Product, concurrency int, activityFunc interface{}) workflow.Future {
+    factories := make([]func(workflow.Context) workflow.Future, len(items))
+    for i, item := range items {
+        item := item
+        factories[i] = func(ctx workflow.Context) workflow.Future {
+            return workflow.ExecuteActivity(ctx, activityFunc, item)
+        }
+    }
+    batch, _ := workflow.NewBatchFuture(ctx, concurrency, factories)
+    return batch
+}
+```
+
+### 2. Progressive Data Processing with Different Priorities
+```go
+func ProcessDataWithPriorities(ctx workflow.Context, data []DataItem) error {
+    // High priority items get more concurrency
+    highPriority := filterByPriority(data, "high")
+    lowPriority := filterByPriority(data, "low")
+    
+    // Process high priority items first with high concurrency
+    highBatch, _ := workflow.NewBatchFuture(ctx, 10, createFactories(highPriority, ProcessHighPriorityActivity))
+    
+    // Wait for high priority to complete, then process low priority with lower concurrency
+    if err := highBatch.Get(ctx, nil); err != nil {
+        return err
+    }
+    
+    lowBatch, _ := workflow.NewBatchFuture(ctx, 3, createFactories(lowPriority, ProcessLowPriorityActivity))
+    return lowBatch.Get(ctx, nil)
+}
+```
+
+### 3. Conditional Batch Processing with Retry Logic
+```go
+func ProcessOrdersWithRetry(ctx workflow.Context, orders []Order) error {
+    // First attempt with normal concurrency
+    factories := make([]func(workflow.Context) workflow.Future, len(orders))
+    for i, order := range orders {
+        order := order
+        factories[i] = func(ctx workflow.Context) workflow.Future {
+            return workflow.ExecuteActivity(ctx, ProcessOrderActivity, order)
+        }
+    }
+    
+    batch, _ := workflow.NewBatchFuture(ctx, 5, factories)
+    if err := batch.Get(ctx, nil); err != nil {
+        // If batch fails, retry failed orders individually with higher concurrency
+        return retryFailedOrders(ctx, orders, 10)
+    }
+    return nil
+}
+```
+
+
+## How It Works Under the Hood
+
+Batch Future leverages Cadence's existing activity infrastructure with controlled concurrency:
+
+1. **Activity Factories**: Creates lazy-evaluated activity functions that aren't executed until needed
+2. **Concurrency Control**: Limits the number of activities running simultaneously
+3. **Queue Management**: Maintains a queue of pending activities and starts new ones as others complete
+4. **Future Management**: Returns a single future that completes when all activities finish
+5. **Error Propagation**: If any activity fails, the entire batch can be cancelled or retried
+
+## Getting Started
+
+Ready to supercharge your workflows? Here's how to get started:
+
+### 1. Update Your Go Client
+Make sure you're using the latest version of the Cadence Go client:
+
+```bash
+go get github.com/uber/cadence-go-client@latest
+```
+
+### 2. Try the Sample
+Check out our [Batch Future sample](https://github.com/cadence-workflow/cadence-samples/tree/master/cmd/samples/batch) to see it in action.
+
+### 3. Migrate Your Workflows
+Identify workflows that process multiple items and convert them to use Batch Future:
+
+```go
+// Before: Uncontrolled concurrency
+var futures []workflow.Future
+for _, item := range items {
+    future := workflow.ExecuteActivity(ctx, ProcessItem, item)
+    futures = append(futures, future)
+}
+for _, future := range futures {
+    if err := future.Get(ctx, nil); err != nil {
+        return err
+    }
+}
+
+// After: Controlled concurrency with Batch Future
+factories := make([]func(workflow.Context) workflow.Future, len(items))
+for i, item := range items {
+    item := item // Capture loop variable
+    factories[i] = func(ctx workflow.Context) workflow.Future {
+        return workflow.ExecuteActivity(ctx, ProcessItem, item)
+    }
+}
+batch, err := workflow.NewBatchFuture(ctx, 3, factories) // Limit to 3 concurrent
+if err != nil {
+    return err
+}
+return batch.Get(ctx, nil)
+```
+
+## Best Practices
+
+- **Choose Appropriate Concurrency**: Start with 3-5 concurrent activities and adjust based on downstream service capacity
+- **Activity Factories**: Always capture loop variables in closures to avoid race conditions
+- **Error Handling**: Implement proper error handling for individual activity failures
+- **Resource Management**: Consider memory usage for large batches
+- **Monitoring**: Use heartbeats for long-running activities within the batch
+
+
+## Try It Today!
+
+Batch Future is available now in the latest Cadence Go client. We can't wait to see how you use it to optimize your workflows!
+
+Have questions or feedback? Join our [Slack community](http://t.uber.com/cadence-slack) or open an issue on [GitHub](https://github.com/cadence-workflow/cadence-go-client).
+
+Happy coding, and here's to faster, more efficient workflows!