postgresql / postgresql_extensible: db label (dbname) changed

[hloeung]

Relevant telegraf.conf

[[inputs.postgresql_extensible]]
  address = "dbname=telegraf host=10.131.124.172 password=my-very-secure-password-redacted port=5432 user=jujuadmin_telegraf"
  # Using the charm default server.
  outputaddress = "10.131.124.172"

Logs from Telegraf

2023-09-21T04:16:06Z I! Starting Telegraf 1.28.1 brought to you by InfluxData the makers of InfluxDB
2023-09-21T04:16:06Z I! Available plugins: 240 inputs, 9 aggregators, 29 processors, 24 parsers, 59 outputs, 5 secret-stores
2023-09-21T04:16:06Z I! Loaded inputs: bond cgroup conntrack cpu disk diskio exec (7x) internal kernel_vmstat mem net netstat nstat postgresql_extensible processes socket_listener swap system
2023-09-21T04:16:06Z I! Loaded aggregators:
2023-09-21T04:16:06Z I! Loaded processors:
2023-09-21T04:16:06Z I! Loaded secretstores:
2023-09-21T04:16:06Z I! Loaded outputs: prometheus_client
2023-09-21T04:16:06Z I! Tags enabled: host=prod-ua-db:postgresql-4 juju_application=postgresql juju_model=prod-ua-db juju_unit=postgresql-4
2023-09-21T04:16:06Z I! [agent] Config: Interval:10s, Quiet:false, Hostname:"prod-ua-db:postgresql-4", Flush Interval:10s
2023-09-21T04:16:06Z D! [agent] Initializing plugins
2023-09-21T04:16:06Z W! DeprecationWarning: Value "false" for option "ignore_protocol_stats" of plugin "inputs.net" deprecated since version 1.27.3 and will be removed in 1.36.0: use the 'inputs.nstat' plugin instead
2023-09-21T04:16:06Z D! [agent] Connecting outputs
2023-09-21T04:16:06Z D! [agent] Attempting connection to [outputs.prometheus_client]
2023-09-21T04:16:06Z I! [outputs.prometheus_client] Listening on http://[::]:9103/metrics
2023-09-21T04:16:06Z D! [agent] Successfully connected to outputs.prometheus_client
2023-09-21T04:16:06Z D! [agent] Starting service inputs
2023-09-21T04:16:06Z I! [inputs.socket_listener] Listening on tcp://127.0.0.1:8094

System info

Telegraf 1.28.1, Ubuntu 20.04.6 LTS

Docker

No response

Steps to reproduce

1. Install Telegraf
2. Setup Postgresql
3. Add inputs.postgresql_extensible config snippet using a DSN config string to connect
   ...

Expected behavior

Using an older telegraf, 1.25.0, we get this:

$ curl -s localhost:9103/metrics | grep '^postgresql_lag'
postgresql_lag_bytes{db="postgres",host="prod-ua-db:postgresql-2",replica="master",server="10.xxx.xxx.xxx",standby="10.xxx.xxx.xxx"} 0

Actual behavior

Using a newer telegraf, 1.28.1 with patches from Josh per #13965), we now get this:

$ curl -s localhost:9103/metrics | grep '^postgresql_lag'
postgresql_lag_bytes{db="10.xxx.xxx",host="prod-ua-db:postgresql-2",replica="master",server="10.xxx.xxx.xxx",standby="10.xxx.xxx.xxx"} 0

Additional info

It looks like another fallout from #13602 where the db label was once postgres is now changed:

            default:
-                   if _, err := dbname.WriteString("postgres"); err != nil {
+                   database, err := p.GetConnectDatabase(tagAddress)
+                   if err != nil {
+                           return err
+                   }
+                   if _, err := dbname.WriteString(database); err != nil {
                            return err
                    }

[powersj]

This whole logic is a bit of a mess :\ I think I have restored the behavior given that you are setting the output address, we should instead return postgres. I have updated the test case and put up #14007.

[powersj]

@hloeung hoping to land this with Monday's v1.27.2. Would you have time to confirm the new diff restores the previous functionality?

Thanks!

[hloeung]

Unfortunately, I'm going away this long weekend without access to work stuff, public holiday here in AU. Happy to test it Tuesday when I return, if you can wait?

Thanks for your time.

[powersj]

No worries, we can grab it in the next point release. Enjoy your holiday!

[hloeung]

@powersj, tested package looks good to me:

$ curl -s localhost:9103/metrics | grep '^postgresql_lag'
postgresql_lag_bytes{db="10.xxx.xxx.xxx",host="prod-ua-db:postgresql-6",juju_application="postgresql",juju_model="prod-ua-db",juju_model_uuid="036db83c-6077-4ae0-8dcc-ebeb2bdda852",juju_unit="postgresql-6",replica="master",server="10.xxx.xxx.xxx",standby="10.xxx.xxx.xxx"} 8208
$ sudo dpkg -i telegraf_1.29.0~529afb53-0_amd64.deb
(Reading database ... 103685 files and directories currently installed.)
Preparing to unpack telegraf_1.29.0~529afb53-0_amd64.deb ...
Unpacking telegraf (1.29.0-0) over (1.28.1+git-868f75eee~202309220113~ubuntu23.04.1) ...
Setting up telegraf (1.29.0-0) ...
$ curl -s localhost:9103/metrics | grep '^postgresql_lag'
postgresql_lag_bytes{db="postgres",host="prod-ua-db:postgresql-6",juju_application="postgresql",juju_model="prod-ua-db",juju_model_uuid="036db83c-6077-4ae0-8dcc-ebeb2bdda852",juju_unit="postgresql-6",replica="master",server="10.xxx.xxx.xxx",standby="10.xxx.xxx.xxx"} 17872

So db="postgres" from the above. Thanks.