"cannot extract value from json by path "$.buffers_backend_fsync": no data matches "

[Jaceqp]

Hi there...
zabbix 7.4.2 +Postgres17.
It's a preshrinked mysql and migrated to psql DB btw.
I got some errors in zabbix-server.log can anyone help me analyze?

1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:122204.384 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":589,"checkpoints_req":9,"c                                             heckpoint_write_time":74246929,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:122204.384 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":589,"checkpoints_req":9,"checkpo                                             int_write_time":74246929,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:122604.385 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":589,"checkpoints_req":9,"c                                             heckpoint_write_time":74465233,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:122604.385 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":589,"checkpoints_req":9,"checkpo                                             int_write_time":74465233,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356063:20260313:122653.290 forced reloading of the snmp cache on [poller #4]
356065:20260313:122653.612 forced reloading of the snmp cache on [poller #5]
356059:20260313:122653.660 forced reloading of the snmp cache on [poller #1]
356061:20260313:122653.881 forced reloading of the snmp cache on [poller #3]
356060:20260313:122653.889 forced reloading of the snmp cache on [poller #2]
356069:20260313:122658.757 forced reloading of the snmp cache on [unreachable poller #3]
356067:20260313:122658.887 forced reloading of the snmp cache on [unreachable poller #1]
356068:20260313:122658.941 forced reloading of the snmp cache on [unreachable poller #2]
356078:20260313:122658.955 forced reloading of the snmp cache on [unreachable poller #10]
356072:20260313:122659.588 forced reloading of the snmp cache on [unreachable poller #6]
356049:20260313:122704.384 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":590,"checkpoints_req":9,"checkpoint_write_time":74465233,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:122704.384 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":590,"checkpoints_req":9,"checkpoint_write_time":74465233,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356077:20260313:122704.392 forced reloading of the snmp cache on [unreachable poller #9]
356075:20260313:122704.662 forced reloading of the snmp cache on [unreachable poller #8]
356082:20260313:122704.723 forced reloading of the snmp cache on [unreachable poller #11]
356074:20260313:122704.736 forced reloading of the snmp cache on [unreachable poller #7]
356083:20260313:122704.756 forced reloading of the snmp cache on [unreachable poller #12]
356071:20260313:122704.757 forced reloading of the snmp cache on [unreachable poller #5]
356070:20260313:122705.164 forced reloading of the snmp cache on [unreachable poller #4]
356049:20260313:123104.384 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":590,"checkpoints_req":9,"checkpoint_write_time":74688957,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:123104.384 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":590,"checkpoints_req":9,"checkpoint_write_time":74688957,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:123204.387 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":591,"checkpoints_req":9,"checkpoint_write_time":74688957,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:123204.387 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":591,"checkpoints_req":9,"checkpoint_write_time":74688957,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:123604.387 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":591,"checkpoints_req":9,"checkpoint_write_time":74905547,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:123604.387 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":591,"checkpoints_req":9,"checkpoint_write_time":74905547,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:123704.386 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":592,"checkpoints_req":9,"checkpoint_write_time":74905547,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:123704.386 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":592,"checkpoints_req":9,"checkpoint_write_time":74905547,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:124104.391 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":592,"checkpoints_req":9,"checkpoint_write_time":75136146,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:124104.391 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":592,"checkpoints_req":9,"checkpoint_write_time":75136146,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:124204.387 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":593,"checkpoints_req":9,"checkpoint_write_time":75136146,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:124204.388 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":593,"checkpoints_req":9,"checkpoint_write_time":75136146,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:124604.385 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":593,"checkpoints_req":9,"checkpoint_write_time":75333388,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:124604.385 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":593,"checkpoints_req":9,"checkpoint_write_time":75333388,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path
356049:20260313:124704.385 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend_fsync.rate" changed: Preprocessing failed for: {"checkpoints_timed":594,"checkpoints_req":9,"checkpoint_write_time":75333388,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend_fsync": no data matches the specified path
356049:20260313:124704.385 error reason for "Zabbix server_DB:pgsql.bgwriter.buffers_backend.rate" changed: Preprocessing failed for: {"checkpoints_timed":594,"checkpoints_req":9,"checkpoint_write_time":75333388,"checkpoint_sync_ti...
1. Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path

[cyber]

Failed: cannot extract value from json by path "$.buffers_backend": no data matches the specified path

Your original data just does not seem to contain such "item" like "buffers_backend" ...

[Jaceqp]

Your original data just does not seem to contain such "item" like "buffers_backend" ...

...uhm... sure but.. I do not get it if it's DB related or some internal zabbix setup like trigger issue or what?

[cyber]

I think it is related to somekind of PG monitoring, which pulls some data from DB, but DB in some reason does not provide specific values, what template is looking for. You probably have this template? https://www.zabbix.com/integrations/...tgresql_agent2
There is an item "Get bgwriter" which pulls all stats about bgwriter and then dependent items extract data from it...
I think these are the onea failing.. https://git.zabbix.com/projects/ZBX/...%2F7.4#189-222

by default "Get bgwriter" does not save its data, you can set short period for it like 1h and then you can actually see the incoming data and investigate, whats the reason there...

[Jaceqp]

Am I reading this right that it's not supported on Postgres17 (which I'm using atm)? Could this be the issue?

[cyber]

yes... available on versions prior to 17 means this is not available on 17... and it is most probably your issue..

[Jaceqp]

yes... available on versions prior to 17 means this is not available on 17... and it is most probably your issue..

Yup, I just disabled these components in a "PostgreSQL by Zabbix agent 2" template and log files are now clean.