Hello, I'm encountering a consistent issue with PostgreSQL 15 logical replication and would appreciate any guidance on debugging or resolving this problem.
*Setup:* - Source: PostgreSQL 15.x - Target: PostgreSQL 15.x - Replication: Logical replication using publication/subscription (pgoutput) - Tables: 3 tables (details below) *Table Details:* - Table 1: ~1,300 records, 7 columns, no large objects - Table 2: ~100,000 records, 7 columns, no large objects - Table 3: ~100,000 records, 17 columns, no large objects *Problem:* The initial snapshot and data copy complete successfully for all tables. However, anywhere from 5 minutes to 2 hours after the initial sync, the subscription consistently fails with memory allocation errors like: ``` 2025-06-10 14:14:56.800 UTC [299] ERROR: could not receive data from WAL stream: ERROR: invalid memory alloc request size 1238451248 2025-06-10 14:14:56.805 UTC [1] LOG: background worker "logical replication worker" (PID 299) exited with exit code 1 ``` This occurs whether I replicate all 3 tables together or individually. My initial hypothesis is that large transactions are creating WAL segments that exceed memory limits when sent to the subscriber. However, I haven't been able to confirm this / find the cause. *Questions:* 1. What's the best approach to debug this memory allocation issue? 2. Are there specific PostgreSQL settings I should check ? 3. How can I identify if large transactions are indeed the root cause? *Additional Context:* - This happens consistently across multiple replication attempts - The error size varies but is always requesting > 1GB - No custom logical replication settings currently applied - Subscriber machine has 256 GB of RAM and Ubuntu 20.04 - Can recreate it on different machines I should also mention that we're operating in a managed environment on DigitalOcean, which means we don't have direct access to the WAL logs on the publisher node. This is why the log information above is limited. I understand this constraint makes it more difficult to provide help, but I would really appreciate any insights or suggestions you might have. Thanks, Max
