Error 502 after gitlab upgrade

Gitlab is installed on Debian. Upgrade with sudo apt-get upgrade, new version is 10.5.3-ce.0.

After upgrade, I get
Whoops, GitLab is taking too much time to respond.

When running gitlab-ctl reconfigure, I get this error:

There was an error running gitlab-ctl reconfigure:

bash[migrate gitlab-rails database] (gitlab::database_migrations line 49) had an error: Mixlib::ShellOut::ShellCommandFailed: Expected process to exit with [0], but received ‘1’
---- Begin output of “bash” “/tmp/chef-script20180306-29372-15ca70b” ----
STDOUT: rake aborted!
PG::ConnectionBad: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket “/var/opt/gitlab/postgresql/.s.PGSQL.5432”?
/opt/gitlab/embedded/service/gitlab-rails/lib/tasks/gitlab/db.rake:49:in block (3 levels) in <top (required)>' /opt/gitlab/embedded/bin/bundle:23:in load’
/opt/gitlab/embedded/bin/bundle:23:in `’
Tasks: TOP => gitlab:db:configure
(See full trace by running task with --trace)
---- End output of “bash” “/tmp/chef-script20180306-29372-15ca70b” ----
Ran “bash” “/tmp/chef-script20180306-29372-15ca70b” returned 1

Please advise.

Content of /var/opt/gitlab/postgresql, because the error mentioned Unix domain socket “/var/opt/gitlab/postgresql/.s.PGSQL.5432”

drwxr-xr-x  4 gitlab-psql root         107 Mar  6 11:13 .
drwxr-xr-x 18 root        root        4096 Mar  6 11:04 ..
-rw-------  1 gitlab-psql root          52 Nov 21  2016 .profile
-rwx------  1 gitlab-psql gitlab-psql  767 Mar 20  2017
drwx------ 19 gitlab-psql gitlab-psql 4096 Mar  6 11:13 data
drwx------ 14 gitlab-psql root        4096 Mar 20  2017 data.9.2.18
-rwx------  1 gitlab-psql gitlab-psql   52 Mar 20  2017

So to my understanding, Gitlab has an embedded postgresql database, and Gitlab is unable to connect to that embedded postgresql database, because it expects to find a Unix socket file, which does not exist?

Is that correct?