docker + golang lib/pq "dial tcp 127.0.0.1:5432: connect: connection refused"

Question

sql.Open() wouldn't error:

if db, err = sql.Open("postgres", url); err != nil {
    return nil, fmt.Errorf("Postgres connect error : (%v)", err)
}

but db.Ping() would error:

if err = db.Ping(); err != nil {
    return nil, fmt.Errorf("Postgres ping error : (%v)", err)
}

and it was simply because the lib/pq connection string wouldn't connect from within a docker container with the seperated connection parameters.

For example:

url := fmt.Sprintf("user=%v password=%v host=%v port=%v dbname=%v",
    rs.conf.Redshift.User,
    rs.conf.Redshift.Password,
    rs.conf.Redshift.Host,
    rs.conf.Redshift.Port,
    rs.conf.Redshift.DB)

Solution

Using the connection string as a URL worked:

    url := fmt.Sprintf("postgres://%v:%v@%v:%v/%v?sslmode=disable",
        pql.conf.Postgres.User,
        pql.conf.Postgres.Password,
        pql.conf.Postgres.Host,
        pql.conf.Postgres.Port,
        pql.conf.Postgres.DB)

See lib/pq docs here: https://godoc.org/github.com/lib/pq

I was stuck on this for more than a day and I owe the fix to Nikolay Sandalov's comment here in GitHub: https://github.com/coreos/clair/issues/134#issuecomment-491300639

Thank you, Nikolay 🙇🏻‍♂️

Comments

[Shepmaster]

FWIW, you don't have to close your question, and we aren't trying to say you are doing it wrong, but I am saying that what you have described isn't an effective debugging technique. Pop into the chat if you want. Please flag this comment as "no longer needed" once you see it to keep this Q&A tidy.

[Mikeumus]

@Shepmaster, I'm here now: meta.stackoverflow.com/questions/334761/… my luck right now is 💯

[Shepmaster]

weird. It looks like you have some weird vestigial account chat.stackoverflow.com/users/244193/mikeumus

[mondayguy]

Worked for me, plussed from 2 accounts=)

[kokemomuke]

Worked like charm