fix(webapp): separate the webhook replication database connection

Add `WEBHOOK_DELIVERIES_REPLICATION_DATABASE_URL` so webhook delivery
replication to ClickHouse can use a direct PostgreSQL connection with
its own credentials while application queries use a pooler. When unset,
replication continues to use `WEBHOOK_DATABASE_URL`, falling back to
`DATABASE_URL`.

Mono-RevId: 9991ab7c7dd7df8f00e3a93a94ca2b8ad02bf4cf

Author: ericallam

apps/webapp/app/env.server.ts

@@ -2154,6 +2154,12 @@ const EnvironmentSchema = z
     // slot and publication so the two consume independently. The source table is
     // a partitioned parent, so the publication is created with
     // publish_via_partition_root.
+    // Direct PostgreSQL connection with replication privileges. When unset, use the webhook
+    // writer URL, then DATABASE_URL; those fallbacks must also support logical replication.
+    WEBHOOK_DELIVERIES_REPLICATION_DATABASE_URL: z
+      .string()
+      .refine(isValidDatabaseUrl, "WEBHOOK_DELIVERIES_REPLICATION_DATABASE_URL is invalid")
+      .optional(),
     WEBHOOK_DELIVERIES_REPLICATION_CLICKHOUSE_URL: z.string().optional(),
     WEBHOOK_DELIVERIES_REPLICATION_ENABLED: z.string().default("0"),
     WEBHOOK_DELIVERIES_REPLICATION_SLOT_NAME: z

apps/webapp/app/services/webhookDeliveriesReplicationInstance.server.ts

@@ -24,8 +24,9 @@ function initializeWebhookDeliveriesReplicationInstance() {
 
   const service = new WebhookDeliveriesReplicationService({
     clickhouseFactory,
-    // Follows the webhook writer DB (where WebhookDelivery physically lives once split).
-    pgConnectionUrl: env.WEBHOOK_DATABASE_URL ?? DATABASE_URL,
+    // Replication needs a direct connection even when webhook queries use a pooler.
+    pgConnectionUrl:
+      env.WEBHOOK_DELIVERIES_REPLICATION_DATABASE_URL ?? env.WEBHOOK_DATABASE_URL ?? DATABASE_URL,
     serviceName: "webhook-deliveries-replication",
     slotName: env.WEBHOOK_DELIVERIES_REPLICATION_SLOT_NAME,
     publicationName: env.WEBHOOK_DELIVERIES_REPLICATION_PUBLICATION_NAME,

docs/self-hosting/env/webapp.mdx

@@ -23,6 +23,7 @@ mode: "wide"
 | **Postgres**                                     |          |                       |                                                                                                                    |
 | `DATABASE_URL`                                   | Yes      | —                     | PostgreSQL connection string.                                                                                      |
 | `DIRECT_URL`                                     | Yes      | —                     | Direct DB connection string used for migrations etc.                                                               |
+| `WEBHOOK_DELIVERIES_REPLICATION_DATABASE_URL` | No | `WEBHOOK_DATABASE_URL`, then `DATABASE_URL` | Direct PostgreSQL connection for webhook delivery replication to ClickHouse. Must target the database containing `WebhookDelivery` and use credentials with replication privileges. Set this when the webhook runtime connection uses a pooler. |
 | `DATABASE_CONNECTION_LIMIT`                      | No       | 10                    | Max DB connections.                                                                                                |
 | `DATABASE_POOL_TIMEOUT`                          | No       | 60                    | DB pool timeout (s).                                                                                               |
 | `DATABASE_CONNECTION_TIMEOUT`                    | No       | 20                    | DB connect timeout (s).                                                                                            |