Resolving Common PostgreSQL Process Startup Issues in YugabyteDB

This guide outlines common issues that can prevent PostgreSQL processes from starting in YugabyteDB and provides solutions for resolving them.

Common Issues and Solutions

Typographic Mistakes or Incorrect Values in ysql_hba.conf

Symptom:
The PostgreSQL process fails to start, displaying the following error in /var/log/messages if systemdis enabled else displayed in /home/yugabyte/tserver/tserver.err:

2024-10-08 15:37:04.976 IST [68216] LOG:  invalid authentication method "<method>"
2024-10-08 15:37:04.976 IST [68216] CONTEXT:  line 4 of configuration file "/Users/<user>/var/data/pg_data/ysql_hba.conf"
2024-10-08 15:37:04.976 IST [68216] FATAL:  could not load pg_hba.conf
2024-10-08 15:37:04.980 IST [68216] LOG:  database system is shut down

Cause:
This error occurs due to a typographical mistake or incorrect authentication method in the ysql_hba.conf file.

Solution:
• Correct the values in the ysql_hba_conf_csv gflag within the universe configuration.

Typographic Mistakes or Incorrect Values in ysql_pg.conf

Symptom:
The PostgreSQL process fails to start with errors indicating unrecognized configuration parameters. This can be seen in /var/log/messages if systemdis enabled else displayed in /home/yugabyte/tserver/tserver.err:

2024-11-13 05:06:51.019 GMT [77212] LOG:  unrecognized configuration parameter "log_connection" in file "/Users/<user>/var/data/pg_data/ysql_pg.conf" line 726
2024-11-13 05:06:51.019 GMT [77212] FATAL:  configuration file "/Users/<user>/var/data/pg_data/ysql_pg.conf" contains errors

Cause:
The issue arises from an invalid or unsupported parameter in the ysql_pg.conf file.

Solution:
• Correct the values in the ysql_pg_conf_csv gflag within the universe configuration.

Pre-Existing Shared Memory Segment Error

Symptom:
The PostgreSQL process fails to start with the following error in /var/log/messages if systemdis enabled else displayed in /home/yugabyte/tserver/tserver.err:

Nov 18 10:05:28 <hostname> yb-tserver[<id>]: otho8AutFATAL:  pre-existing shared memory block (key 5433001, ID 6) is still in use
Nov 18 10:05:28 <hostname> yb-tserver[<id>]: otho8AutHINT:  Terminate any old server processes associated with data directory "/mnt/d0/pg_data".
Nov 18 10:05:28 <hostname> yb-tserver[<id>]: otho8AutLOG:  database system is shut down

Cause:
This error indicates a pre-existing shared memory segment that conflicts with the PostgreSQL process, often due to an improperly terminated server process.

Solution:
• Remove the shared memory segment using the following command:

ipcrm -M <shared_memory_id>

In the example log above, the shared_memory_id is 6. Replace <shared_memory_id> with the appropriate ID from your logs.

This troubleshooting guide should help you quickly identify and resolve PostgreSQL process startup issues in YugabyteDB. If the issue persists, or if you encounter other errors, contact YugabyteDB support for further assistance.