Samba DC restore fails with empty TimescaleDB

[DavidePrincipi]

During NS8 Samba module restore, the TimescaleDB container may fail while restoring the samba_audit database. The failure is caused by a race condition between CREATE EXTENSION timescaledb, background worker initialization, and the early execution of timescaledb_pre_restore(). As a result, internal TimescaleDB catalog objects are missing when pg_restore starts, causing the restore to abort. The issue is more reproducible when the database to restore is almost empty.

Steps to reproduce

• Install NS8 and the Samba DC with VPN IP address
• Generate a backup where the samba_audit database is empty or almost empty
• Restore the backup on a new cluster or node
• Observe the Samba module restore task failing at the TimescaleDB restore step

Expected behavior

The Samba module restore completes successfully, restoring (or recreating) the samba_audit database even when it contains little or no data.

Actual behavior

The restore aborts with errors like:

• relation _timescaledb_catalog.chunk_index does not exist
• function _timescaledb_functions.insert_blocker() does not exist

The failure occurs after timescaledb_pre_restore() terminates TimescaleDB background workers before internal catalogs are fully initialized.

Log excerpt:

Restore samba_audit data in TimescaleDB:

CREATE DATABASE
CREATE EXTENSION

2026-01-26 15:29:26.416 UTC [41] LOG:  TimescaleDB background worker launcher connected to shared catalogs

timescaledb_pre_restore
(1 row)

2026-01-26 15:29:26.861 UTC [52] FATAL:  terminating background worker "TimescaleDB Background Worker Scheduler" due to administrator command
2026-01-26 15:29:26.864 UTC [35] LOG:  background worker "TimescaleDB Background Worker Scheduler" (PID 52) exited with exit code 1

2026-01-26 15:29:26.889 UTC [54] ERROR:  relation "_timescaledb_catalog.chunk_index" does not exist
2026-01-26 15:29:26.889 UTC [54] STATEMENT:  COPY _timescaledb_catalog.chunk_index (...) FROM stdin;

2026-01-26 15:29:26.910 UTC [54] ERROR:  function _timescaledb_functions.insert_blocker() does not exist
2026-01-26 15:29:26.910 UTC [54] STATEMENT:  CREATE TRIGGER ts_insert_blocker ...

Components

• NethServer Core 3.16
• Samba DC 3.4.1

See also

• TimescaleDB documentation on timescaledb_pre_restore() and restore ordering
• Internal discussion about Samba restore failures with empty audit DBs https://mattermost.nethesis.it/nethesis/pl/4xdtnseanfdoxmzg85cnjxo8uw

Acknowledgements

Thanks to @nrauso

[DavidePrincipi]

In Testing 3.4.2-dev.3

Test case 1

Check the bug is not reproducible with empty DB.

Test case 2

Check the file server restoration with data in TimescaleDB still works.

---

QA note:

The fix inserts a wait loop to prevent a race during timescale restoration. The journalctl -o short-precise output shows sub-second timestamps, and the half-second delay introduced by the fix:

Jan 27 15:30:36.357607 rl1 agent@samba2[2205]: CREATE EXTENSION                                                                                                                                                                                
Jan 27 15:30:36.862767 rl1 agent@samba2[2205]: DO   

[nrauso]

TimescaleDB is now correctly restored in both scenarios, but QA identified another issue: after the restore, the samba_audit database is no longer accessible.

 
Here is the relevant log:

Jan 28 15:44:58.247008 myrocky.nethe.eu timescaledb[15016]: 2026-01-28 14:44:58.246 UTC [109] FATAL:  password authentication failed for user "samba_audit"
Jan 28 15:44:58.247177 myrocky.nethe.eu timescaledb[15016]: 2026-01-28 14:44:58.246 UTC [109] DETAIL:  Connection matched file "/var/lib/postgresql/data/pg_hba.conf" line 128: "host all all all scram-sha-256"
Jan 28 15:44:58.284091 myrocky.nethe.eu timescaledb[15016]: 2026-01-28 14:44:58.284 UTC [110] FATAL:  password authentication failed for user "samba_audit"
Jan 28 15:44:58.284258 myrocky.nethe.eu timescaledb[15016]: 2026-01-28 14:44:58.284 UTC [110] DETAIL:  Connection matched file "/var/lib/postgresql/data/pg_hba.conf" line 128: "host all all all scram-sha-256"