capistrano, rails, PG::ConnectionBad: fe_sendauth: no password supplied - ruby-on-rails

Question

I'm trying to run Capistrano for a rails app with Postgres on Ubuntu 14, I ran into a password error during rake db:migrate-
DEBUG [2823f146] Command: cd /home/ben/apps/mll/releases/20160414014303 && ( export RBENV_ROOT="$HOME/.rbenv" RBENV_VERSION="2.0.0-p645" RAILS_ENV="production" ; $HOME/.rbenv/bin/rbenv exec bundle exec rake db:migrate )
DEBUG [2823f146] rake aborted!
PG::ConnectionBad: fe_sendauth: no password supplied
I tried every solution to similar posts but no luck. For kicks I also tried running just that command in the remote app dir and got the following:
PG::ConnectionBad: FATAL: password authentication failed for user "mll"
FATAL: password authentication failed for user "mll"
This is interesting because it's using my database name as my username. See database.yml below, so for the hell of it I added a mll role, and lo and behold it worked when just running rake db:migrate. I tried running Capistrano again though with this new role, and still no luck.
Is it a reasonable guess that the username is not being accessed/stored properly? Any way for me to test that? I manually ALTER ROLE ben WITH PASSWORD 'mypw'; for both my ben and mll roles, and nothing.
My database.yml:
defaults: &default
adapter: sqlite3
encoding: utf8
development:
<<: *default
database: db/development.sqlite3
test:
<<: *default
database: db/development.sqlite3_test
production:
<<: *default
host: localhost
adapter: postgresql
encoding: utf8
database: mll
pool: 5
username: <%= ENV['DATABASE_USER'] %>
password: <%= ENV['DATABASE_PASSWORD'] %>
\du:
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
ben | Superuser, Create role, Create DB | {}
mll | Superuser, Create role, Create DB | {}
postgres | Superuser, Create role, Create DB, Replication | {}
I read changing md5 to trust helped some people, I tried that, but I'm unsure how to restart, all commands I've seen haven't worked for me.
pg_hba.conf:
local all postgres peer
# TYPE DATABASE USER ADDRESS METHOD
local all all peer
host all all 127.0.0.1/32 md5
host all all ::1/128 md5

Answer 1

You should use "trust" under method for localhost in pg_hba.conf. Note that this means all connections from localhost will be able to login as any user, which is probably fine as long as you're using this for development.
# "local" is for Unix domain socket connections only
local all all trust
# IPv4 local connections:
host all all 127.0.0.1/32 trust
# IPv6 local connections:
host all all ::1/128 trust
After changing your pg_hba.conf you can restart postgres with pg_ctl reload

Answer 2

The best practice to resolve the issue is -
Add the below gem in your Gemfile under development group and bundle install.
gem 'capistrano-postgresql'
Add the below line in Capfile
require 'capistrano/postgresql'
Add below lines in config/deploy.rb or in config/deploy/*.rb
set :pg_password, ENV['DATABASE_PASSWORD']
set :pg_ask_for_password, true