feat(webapp): add option to disable PostgreSQL task-event writes (#4242)

## Summary

Adds `EVENT_REPOSITORY_POSTGRES_WRITES_DISABLED` (default off), which
makes the task-event store skip all PostgreSQL `TaskEvent` writes. It's
for deployments that store task events in ClickHouse
(`EVENT_REPOSITORY_DEFAULT_STORE=clickhouse_v2`) and no longer want the
PostgreSQL copy.

## How it works

The guard sits at the single postgres write boundary,
`TaskEventStore.create` / `createMany`, so it covers every write path
(OTLP ingestion and run-lifecycle events) with one check. Reads are
untouched (`findMany` / trace queries / streaming), so existing
PostgreSQL events remain readable.

Leave it off unless the default store is `clickhouse_v2`, otherwise task
events for any run still routed to PostgreSQL would be dropped.

.server-changes/disable-postgres-task-event-writes.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: feature
+---
+
+Added `EVENT_REPOSITORY_POSTGRES_WRITES_DISABLED` to skip all PostgreSQL task-event writes for deployments that store task events in ClickHouse. Leave it off unless `EVENT_REPOSITORY_DEFAULT_STORE` is `clickhouse_v2`, otherwise task events are lost.

apps/webapp/app/env.server.ts

@@ -1860,6 +1860,7 @@ const EnvironmentSchema = z
       .enum(["postgres", "clickhouse", "clickhouse_v2"])
       .default("postgres"),
     EVENT_REPOSITORY_DEBUG_LOGS_DISABLED: BoolEnv.default(false),
+    EVENT_REPOSITORY_POSTGRES_WRITES_DISABLED: BoolEnv.default(false),
     EVENTS_CLICKHOUSE_MAX_TRACE_SUMMARY_VIEW_COUNT: z.coerce.number().int().default(25_000),
     EVENTS_CLICKHOUSE_MAX_TRACE_DETAILED_SUMMARY_VIEW_COUNT: z.coerce.number().int().default(5_000),
     EVENTS_CLICKHOUSE_MAX_LIVE_RELOADING_SETTING: z.coerce.number().int().default(2000),

apps/webapp/app/v3/eventRepository/eventRepository.server.ts

@@ -157,14 +157,23 @@ export class EventRepository implements IEventRepository {
   }
 
   private async insertImmediate(event: CreateEventInput) {
+    if (env.EVENT_REPOSITORY_POSTGRES_WRITES_DISABLED) {
+      return;
+    }
     await this.#flushBatch(nanoid(), [this.#createableEventToPrismaEvent(event)]);
   }
 
   insertMany(events: CreateEventInput[]) {
+    if (env.EVENT_REPOSITORY_POSTGRES_WRITES_DISABLED) {
+      return;
+    }
     this._flushScheduler.addToBatch(events.map(this.#createableEventToPrismaEvent));
   }
 
   async insertManyImmediate(events: CreateEventInput[]) {
+    if (env.EVENT_REPOSITORY_POSTGRES_WRITES_DISABLED) {
+      return;
+    }
     await this.#flushBatchWithReturn(nanoid(), events.map(this.#createableEventToPrismaEvent));
   }
 
@@ -1018,7 +1027,7 @@ export class EventRepository implements IEventRepository {
     if (options.immediate) {
       await this.insertImmediate(event);
     } else {
-      this._flushScheduler.addToBatch([this.#createableEventToPrismaEvent(event)]);
+      this.insertMany([event]);
     }
   }
 
@@ -1152,7 +1161,7 @@ export class EventRepository implements IEventRepository {
     if (options.immediate) {
       await this.insertImmediate(event);
     } else {
-      this._flushScheduler.addToBatch([this.#createableEventToPrismaEvent(event)]);
+      this.insertMany([event]);
     }
 
     return result;

docs/self-hosting/env/webapp.mdx

@@ -135,6 +135,7 @@ mode: "wide"
 | `SERVER_OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT`  | No       | 8192                  | OTel span attribute value length limit.                                                                            |
 | **Task events**                                  |          |                       |                                                                                                                    |
 | `EVENT_REPOSITORY_DEFAULT_STORE`                 | No       | postgres              | Where to store task events. Set to `clickhouse_v2` to store in ClickHouse (recommended for production).            |
+| `EVENT_REPOSITORY_POSTGRES_WRITES_DISABLED`      | No       | 0                     | Skip all PostgreSQL task-event writes (set to `1`). Only enable when `EVENT_REPOSITORY_DEFAULT_STORE` is `clickhouse_v2`, otherwise task events are lost. |
 | **Realtime**                                     |          |                       |                                                                                                                    |
 | `REALTIME_STREAM_VERSION`                        | No       | v1                    | Stream version exposed to tasks via the `TRIGGER_REALTIME_STREAM_VERSION` variable. Distinct from `REALTIME_STREAMS_DEFAULT_VERSION`. One of `v1`, `v2`. |
 | `REALTIME_STREAM_MAX_LENGTH`                     | No       | 1000                  | Realtime stream max length.                                                                                        |