Rails server not working on Cloud9 - ruby-on-rails

Question

A Rails newbie here. I'm having problem with cloned Shopify app to develop on Cloud9. I need to run on rails s -b $IP -p $PORT to see a preview, but i can't access to first page at all. it showed 500 server error (full msg: A static HTML page can contain a simple dependency free script to set the top bar to a 500 server error. This page can be found in 'public/500.html'.)
I tried to find solution here and here. Both of them suggest to modify pg_hba.conf But I check my file and it's the same as them so I didn't modify it at all.
I did try to change my database.yml from host: localhost -> host: /var/run/postgresql but I got another error msg. It seems not a solution.
Could you help me?
Here's my log
icys#c_app:~/workspace (master) $ rails s -b $IP -p $PORT
=> Booting Thin
=> Rails 4.2.0 application starting in development on http://0.0.0.0:8080
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
Thin web server (v1.6.3 codename Protein Powder)
Maximum connections set to 1024
Listening on 0.0.0.0:8080, CTRL+C to stop
Started GET "/" for 171.96.244.172 at 2015-09-01 13:44:42 +0000
PG::ConnectionBad (fe_sendauth: no password supplied
):
activerecord (4.2.0) lib/active_record/connection_adapters/postgresql_adapter.rb:651:in `initialize'
activerecord (4.2.0) lib/active_record/connection_adapters/postgresql_adapter.rb:651:in `new'
activerecord (4.2.0) lib/active_record/connection_adapters/postgresql_adapter.rb:651:in `connect'
activerecord (4.2.0) lib/active_record/connection_adapters/postgresql_adapter.rb:242:in `initialize'
activerecord (4.2.0) lib/active_record/connection_adapters/postgresql_adapter.rb:44:in `new'
activerecord (4.2.0) lib/active_record/connection_adapters/postgresql_adapter.rb:44:in `postgresql_connection'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:436:in `new_connection'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:446:in `checkout_new_connection'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:422:in `acquire_connection'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:349:in `block in checkout'
/usr/local/rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:348:in `checkout'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:263:in `block in connection'
/usr/local/rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:262:in `connection'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:565:in `retrieve_connection'
activerecord (4.2.0) lib/active_record/connection_handling.rb:113:in `retrieve_connection'
activerecord (4.2.0) lib/active_record/connection_handling.rb:87:in `connection'
activerecord (4.2.0) lib/active_record/query_cache.rb:51:in `restore_query_cache_settings'
activerecord (4.2.0) lib/active_record/query_cache.rb:43:in `rescue in call'
activerecord (4.2.0) lib/active_record/query_cache.rb:31:in `call'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:647:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.2.0) lib/active_support/callbacks.rb:88:in `call'
activesupport (4.2.0) lib/active_support/callbacks.rb:88:in `_run_callbacks'
activesupport (4.2.0) lib/active_support/callbacks.rb:734:in `_run_call_callbacks'
activesupport (4.2.0) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (4.2.0) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/reloader.rb:73:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/remote_ip.rb:78:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.2.0) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.2.0) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.2.0) lib/active_support/tagged_logging.rb:68:in `block in tagged'
activesupport (4.2.0) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (4.2.0) lib/active_support/tagged_logging.rb:68:in `tagged'
railties (4.2.0) lib/rails/rack/logger.rb:20:in `call'
quiet_assets (1.1.0) lib/quiet_assets.rb:27:in `call_with_quiet_assets'
actionpack (4.2.0) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.6.1) lib/rack/methodoverride.rb:22:in `call'
rack (1.6.1) lib/rack/runtime.rb:18:in `call'
activesupport (4.2.0) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
rack (1.6.1) lib/rack/lock.rb:17:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/static.rb:113:in `call'
rack (1.6.1) lib/rack/sendfile.rb:113:in `call'
railties (4.2.0) lib/rails/engine.rb:518:in `call'
railties (4.2.0) lib/rails/application.rb:164:in `call'
rack (1.6.1) lib/rack/content_length.rb:15:in `call'
thin (1.6.3) lib/thin/connection.rb:86:in `block in pre_process'
thin (1.6.3) lib/thin/connection.rb:84:in `catch'
thin (1.6.3) lib/thin/connection.rb:84:in `pre_process'
thin (1.6.3) lib/thin/connection.rb:53:in `process'
thin (1.6.3) lib/thin/connection.rb:39:in `receive_data'
eventmachine (1.0.7) lib/eventmachine.rb:187:in `run_machine'
eventmachine (1.0.7) lib/eventmachine.rb:187:in `run'
thin (1.6.3) lib/thin/backends/base.rb:73:in `start'
thin (1.6.3) lib/thin/server.rb:162:in `start'
rack (1.6.1) lib/rack/handler/thin.rb:19:in `run'
rack (1.6.1) lib/rack/server.rb:286:in `start'
railties (4.2.0) lib/rails/commands/server.rb:80:in `start'
railties (4.2.0) lib/rails/commands/commands_tasks.rb:80:in `block in server'
railties (4.2.0) lib/rails/commands/commands_tasks.rb:75:in `tap'
railties (4.2.0) lib/rails/commands/commands_tasks.rb:75:in `server'
railties (4.2.0) lib/rails/commands/commands_tasks.rb:39:in `run_command!'
railties (4.2.0) lib/rails/commands.rb:17:in `<top (required)>'
bin/rails:4:in `require'
bin/rails:4:in `<main>'
Here's my database.yml
development:
adapter: postgresql
encoding: unicode
database: development
pool: 5
host: localhost
username: action
password:
Here's my pg_hba.conf
# Database administrative login by Unix domain socket
local all postgres peer
# TYPE DATABASE USER ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all peer
# IPv4 local connections:
host all all 127.0.0.1/32 md5
# IPv6 local connections:
host all all ::1/128 md5