postgres_exporter: exclude-databases does not properly work

What did you do? I ran an exporter process including the auto-discover-databases and exclude-databases flags. Also pulling from a custom query files:

exec postgres_exporter --web.listen-address :9189 --disable-default-metrics --auto-discover-databases --exclude-databases postgres,template0,template1 --extend.query-path /tmp/queries.yaml

/tmp/queries.yaml file includes two different queries:

    pg_database:
      query: "SELECT pg_database.datname, pg_database_size(pg_database.datname) as size_bytes FROM pg_database"
      master: true
      metrics:
        - datname:
            usage: "LABEL"
            description: "Name of the database"
        - size_bytes:
            usage: "GAUGE"
            description: "Disk space used by the database"

    pg_database_2:
      query: "SELECT pg_database.datname, pg_database_size(pg_database.datname) as size_bytes FROM pg_database WHERE datname = current_database()"
      master: true
      metrics:
        - datname:
            usage: "LABEL"
            description: "Name of the database"
        - size_bytes:
            usage: "GAUGE"
            description: "Disk space used by the database"

DBs on my instance:

postgres=# \l
                                 List of databases
   Name    |  Owner   | Encoding |  Collate   |   Ctype    |   Access privileges
-----------+----------+----------+------------+------------+-----------------------
 nsoengas  | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =Tc/postgres         +
           |          |          |            |            | postgres=CTc/postgres+
           |          |          |            |            | nsoengas=C/postgres
 postgres  | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
 template0 | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
           |          |          |            |            | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.utf8 | en_US.utf8 | =c/postgres          +
           |          |          |            |            | postgres=CTc/postgres
(4 rows)

postgres=#

What did you expect to see? Since I am using exclude-databases flag and then excluding postgres,template0,template1 DBs, then my expectation is postgres exporter connecting to nsoengas DB and performing the queries on my custom file (/tmp/queries.yaml). According to those queries, pg_database should retrieve datname and size for every single database on given instance. pg_database_2 should ONLY show datname and size for the database I am connected to. I’ve included the proper query filter to do that. So, pg_database_2 should connect to “nsoengas” DB and report its datname and size.

What did you see instead? Under which circumstances? pg_database seems to be “showing” what it suppose to show. However, pg_database_2 is showing “postgres” as datname. Since I explicitly included the filter WHERE datname = current_database() AFAIK it is connecting to “postgres” database and retrieving its size It could be seen while scrapping on the exporter port:

[root@nsoengas-db-0 /]# curl http://localhost:9189/metrics | grep pg_database
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0# HELP pg_database_2_size_bytes Disk space used by the database
# TYPE pg_database_2_size_bytes gauge
pg_database_2_size_bytes{datname="postgres",server="localhost:5432"} 7.526936e+06
# HELP pg_database_size_bytes Disk space used by the database
# TYPE pg_database_size_bytes gauge
pg_database_size_bytes{datname="nsoengas",server="localhost:5432"} 7.58428e+06
pg_database_size_bytes{datname="postgres",server="localhost:5432"} 7.526936e+06
pg_database_size_bytes{datname="template0",server="localhost:5432"} 7.414276e+06
pg_database_size_bytes{datname="template1",server="localhost:5432"} 7.414276e+06
100 51180    0 51180    0     0  4543k      0 --:--:-- --:--:-- --:--:-- 4543k
[root@nsoengas-db-0 /]#

Environment

• System information:

[root@nsoengas-db-0 ~]$ uname -srm
Linux 5.4.17-2102.202.5.el7uek.x86_64 x86_64
[root@nsoengas-db-0 ~]$

• postgres_exporter version:

[root@nsoengas-db-0 /]# postgres_exporter --version
postgres_exporter, version 0.10.0 (branch: HEAD, revision: 57719ba53cac428769aaf3c4c0bb742df3cfca98)
  build user:       root@4dcb2c7f1315
  build date:       20210709-11:49:20
  go version:       go1.16.5
  platform:         linux/amd64
[root@nsoengas-db-0 /]#

• postgres_exporter flags:

exec postgres_exporter --web.listen-address :9189 --disable-default-metrics --auto-discover-databases --exclude-databases postgres,template0,template1 --extend.query-path /tmp/queries.yaml

• PostgresSQL version:

postgres=# SELECT version();
                                                  version
-----------------------------------------------------------------------------------------------------------
 PostgreSQL 9.6.15 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36), 64-bit
(1 row)

postgres=#