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88 lines
2.0 KiB
Markdown
88 lines
2.0 KiB
Markdown
# Pipelines Patterns
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## Fire-and-Forget
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```typescript
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export default {
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async fetch(request, env, ctx) {
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const event = { user_id: '...', event_type: 'page_view', timestamp: new Date().toISOString() };
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ctx.waitUntil(env.STREAM.send([event])); // Don't block response
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return new Response('OK');
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}
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};
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```
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## Schema Validation with Zod
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```typescript
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import { z } from 'zod';
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const EventSchema = z.object({
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user_id: z.string(),
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event_type: z.enum(['purchase', 'view']),
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amount: z.number().positive().optional()
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});
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const validated = EventSchema.parse(rawEvent); // Throws on invalid
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await env.STREAM.send([validated]);
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```
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**Why:** Structured streams drop invalid events silently. Client validation gives immediate feedback.
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## SQL Transform Patterns
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```sql
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-- Filter early (reduce storage)
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INSERT INTO my_sink
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SELECT user_id, event_type, amount
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FROM my_stream
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WHERE event_type = 'purchase' AND amount > 10
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-- Select only needed fields
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INSERT INTO my_sink
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SELECT user_id, event_type, timestamp FROM my_stream
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-- Enrich with CASE
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INSERT INTO my_sink
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SELECT user_id, amount,
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CASE WHEN amount > 1000 THEN 'vip' ELSE 'standard' END as tier
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FROM my_stream
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```
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## Pipelines + Queues Fan-out
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```typescript
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await Promise.all([
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env.ANALYTICS_STREAM.send([event]), // Long-term storage
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env.PROCESS_QUEUE.send(event) // Immediate processing
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]);
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```
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| Need | Use |
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|------|-----|
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| Long-term storage, SQL queries | Pipelines |
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| Immediate processing, retries | Queues |
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| Both | Fan-out pattern |
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## Performance Tuning
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| Goal | Config |
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|------|--------|
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| Low latency | `--roll-interval 10` |
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| Query performance | `--roll-interval 300 --roll-size 100` |
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| Cost optimal | `--compression zstd --roll-interval 300` |
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## Schema Evolution
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Pipelines are immutable. Use versioning:
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```bash
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# Create v2 stream/sink/pipeline
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npx wrangler pipelines streams create events-v2 --schema-file v2.json
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# Dual-write during transition
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await Promise.all([env.EVENTS_V1.send([event]), env.EVENTS_V2.send([event])]);
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# Query across versions with UNION ALL
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```
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