7e5abd504f
Add three DBOS SDK skills with reference documentation for building reliable, fault-tolerant applications with durable workflows. Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
58 lines
2.0 KiB
Markdown
58 lines
2.0 KiB
Markdown
---
|
|
title: Use Messages for Workflow Notifications
|
|
impact: MEDIUM
|
|
impactDescription: Enables reliable inter-workflow and external-to-workflow communication
|
|
tags: communication, messages, send, recv, notification
|
|
---
|
|
|
|
## Use Messages for Workflow Notifications
|
|
|
|
Use `dbos.Send` to send messages to a workflow and `dbos.Recv` to receive them. Messages are queued per topic and persisted for reliable delivery.
|
|
|
|
**Incorrect (using external messaging for workflow communication):**
|
|
|
|
```go
|
|
// External message queue is not integrated with workflow recovery
|
|
ch := make(chan string) // Not durable!
|
|
```
|
|
|
|
**Correct (using DBOS messages):**
|
|
|
|
```go
|
|
func checkoutWorkflow(ctx dbos.DBOSContext, orderID string) (string, error) {
|
|
// Wait for payment notification (timeout 120 seconds)
|
|
notification, err := dbos.Recv[string](ctx, "payment_status", 120*time.Second)
|
|
if err != nil {
|
|
return "", err
|
|
}
|
|
|
|
if notification == "paid" {
|
|
_, err = dbos.RunAsStep(ctx, func(ctx context.Context) (string, error) {
|
|
return fulfillOrder(orderID)
|
|
}, dbos.WithStepName("fulfillOrder"))
|
|
return "fulfilled", err
|
|
}
|
|
_, err = dbos.RunAsStep(ctx, func(ctx context.Context) (string, error) {
|
|
return cancelOrder(orderID)
|
|
}, dbos.WithStepName("cancelOrder"))
|
|
return "cancelled", err
|
|
}
|
|
|
|
// Send a message from a webhook handler
|
|
func paymentWebhook(ctx dbos.DBOSContext, workflowID, status string) error {
|
|
return dbos.Send(ctx, workflowID, status, "payment_status")
|
|
}
|
|
```
|
|
|
|
Key behaviors:
|
|
- `Recv` waits for and consumes the next message for the specified topic
|
|
- Returns the zero value if the wait times out, with a `DBOSError` with code `TimeoutError`
|
|
- Messages without a topic can only be received by `Recv` without a topic
|
|
- Messages are queued per-topic (FIFO)
|
|
|
|
**Reliability guarantees:**
|
|
- All messages are persisted to the database
|
|
- Messages sent from workflows are delivered exactly-once
|
|
|
|
Reference: [Workflow Messaging and Notifications](https://docs.dbos.dev/golang/tutorials/workflow-communication#workflow-messaging-and-notifications)
|