Postgres Error running query on database: Could not detect default username

Question

Hi I am trying to monitor postgres SQL with Prometheus. For this purpose I am using this exporter https://github.com/wrouesnel/postgres_exporter

I am starting the exporter in my docker-compose.yml like this:

  exporter-postgres:
    image: wrouesnel/postgres_exporter
    ports:
      - 9113:9113
    environment:
      - DATA_SOURCE_NAME="postgresql://user:pass@localhost:5432/?sslmode=disable" 

When the exporter is trying to access the database errors like this are thrown:

Error running query on database: pg_stat_database pg: Could not detect default username. Please provide one explicitly. file="postgres-exporter.go" line=490

and

Error scanning runtime variable: pg_stat_database pg: Could not detect default username. Please provide one explicitly. file="postgres-exporter.go" line=464

I am not really sure what this message could mean. Also I am not really sure if the issues originates in my docker-compose file, or the exporter.

The lines which throw the error in the postgres-exporter.go are:

// Use SHOW to get the value
row := db.QueryRow(fmt.Sprintf("SHOW %s;", columnName))

var val interface{}
err := row.Scan(&val)
if err != nil {
    log.Errorln("Error scanning runtime variable:", columnName, err)
    continue
}

and

query, er := queryOverrides[namespace]
if er == false {
    query = fmt.Sprintf("SELECT * FROM %s;", namespace)
}

// Don't fail on a bad scrape of one metric
rows, err := db.Query(query)
if err != nil {
    log.Println("Error running query on database: ", namespace, err)
    e.error.Set(1)
    return
}

https://github.com/wrouesnel/postgres_exporter/blob/master/postgres_exporter.go

I am thankful for any help!

Edit:

Here is the connection to the database:

db, err := sql.Open("postgres", e.dsn)

Whereas e.dsn is generated like this:

dsn := os.Getenv("DATA_SOURCE_NAME")

The connection doesn't throw any error

Answer 1

Hey for anyone having a similiar issue in the future:

The problem was this line in the docker-compose.yml

 - DATA_SOURCE_NAME="postgresql://user:pass@localhost:5432/?sslmode=disable" 

Changing it to

 - DATA_SOURCE_NAME=postgresql://user:pass@localhost:5432/?sslmode=disable

(Without the quotes) made everything work :)