Hello, hackers
When the current HEAD fails during logical decoding, the failure increments txns count in pg_stat_replication_slots - [1] and adds the transaction size to the sum of bytes in the same repeatedly on the publisher, until the problem is solved. One of the good examples is duplication error on the subscriber side and this applies to both streaming and spill cases as well. This update prevents users from grasping the exact number and size of successful and unsuccessful transactions. Accordingly, we need to have new columns of failed transactions that will work to differentiate both of them for all types, which means spill, streaming and normal transactions. This will help users to measure the exact status of logical replication. Attached file is the POC patch for this. Current design is to save failed stats data in the ReplicationSlot struct. This is because after the error, I'm not able to access the ReorderBuffer object. Thus, I chose the object where I can interact with at the ReplicationSlotRelease timing. Below is one example that I can get on the publisher, after the duplication error on the subscriber caused by insert is solved. postgres=# select * from pg_stat_replication_slots; -[ RECORD 1 ]-------+------ slot_name | mysub spill_txns | 0 spill_count | 0 spill_bytes | 0 failed_spill_txns | 0 failed_spill_bytes | 0 stream_txns | 0 stream_count | 0 stream_bytes | 0 failed_stream_txns | 0 failed_stream_bytes | 0 total_txns | 4 total_bytes | 528 failed_total_txns | 3 failed_total_bytes | 396 stats_reset | Any ideas and comments are welcome. [1] - https://www.postgresql.org/docs/devel/monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW Best Regards, Takamichi Osumi
failed_transaction_stats_POC_v01.patch
Description: failed_transaction_stats_POC_v01.patch
