导轨在Heroku 4应用程式500ing，但在日志中没有错误消息(Rails 4 app on H

我做了一个新的Rails 4测试版的应用程序，并将其部署到Heroku上（通过Procfile使用Ruby 2.0.0和独角兽）。

它运行良好与当地foreman start ，但是当我访问了部署应用程序的主页，我只是得到标准的Heroku 500错误：

We're sorry, but something went wrong.
If you are the application owner check the logs for more information.

然而，在日志中， 没有错误 。我不知道是什么原因造成的500。

这里是我最后的输出git push heroku master ：

Counting objects: 6, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (4/4), 656 bytes, done.
Total 4 (delta 2), reused 0 (delta 0)

-----> Ruby/Rails app detected
-----> Using Ruby version: ruby-2.0.0
-----> Installing dependencies using Bundler version 1.3.2
       Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin --deployment
       Using rake (10.0.4)
       Using i18n (0.6.4)
       Using minitest (4.7.3)
       Using multi_json (1.7.2)
       Using atomic (1.1.8)
       Using thread_safe (0.1.0)
       Using tzinfo (0.3.37)
       Using activesupport (4.0.0.beta1)
       Using builder (3.1.4)
       Using erubis (2.7.0)
       Using rack (1.5.2)
       Using rack-test (0.6.2)
       Using actionpack (4.0.0.beta1)
       Using mime-types (1.23)
       Using polyglot (0.3.3)
       Using treetop (1.4.12)
       Using mail (2.5.3)
       Using actionmailer (4.0.0.beta1)
       Using activemodel (4.0.0.beta1)
       Using activerecord-deprecated_finders (0.0.3)
       Using arel (4.0.0)
       Using activerecord (4.0.0.beta1)
       Using coffee-script-source (1.6.2)
       Using execjs (1.4.0)
       Using coffee-script (2.2.0)
       Using json (1.7.7)
       Using rdoc (3.12.2)
       Using thor (0.18.1)
       Using railties (4.0.0.beta1)
       Using coffee-rails (4.0.0)
       Using hike (1.2.2)
       Using jbuilder (1.0.2)
       Using jquery-rails (2.2.1)
       Using kgio (2.8.0)
       Using mysql2 (0.3.11)
       Using bundler (1.3.2)
       Using tilt (1.3.7)
       Using sprockets (2.9.3)
       Using sprockets-rails (2.0.0.rc4)
       Using rails (4.0.0.beta1)
       Using raindrops (0.11.0)
       Using sass (3.2.8)
       Using sass-rails (4.0.0.rc1)
       Using turbolinks (1.1.1)
       Using uglifier (2.0.1)
       Using unicorn (4.6.2)
       Your bundle is complete! It was installed into ./vendor/bundle
       Cleaning up the bundler cache.
-----> Preparing app for Rails asset pipeline
       Running: rake assets:precompile
       I, [2013-04-23T22:28:44.559735 #871]  INFO -- : Writing /tmp/build_33m76p0rij8a5/public/assets/rails-d8fb6a2617998f32edf5edb354fc5326.png
       I, [2013-04-23T22:28:49.911890 #871]  INFO -- : Writing /tmp/build_33m76p0rij8a5/public/assets/application-d4a508061cd56ce9e544945495285e0c.js
       I, [2013-04-23T22:28:50.120141 #871]  INFO -- : Writing /tmp/build_33m76p0rij8a5/public/assets/application-a3b89b66a8471f3e75abb239e3b35c7d.css
       Asset precompilation completed (8.30s)
-----> Rails plugin injection
-----> Discovering process types
       Procfile declares types      -> web
       Default types for Ruby/Rails -> console, rake, worker

-----> Compiled slug size: 35.0MB
-----> Launching... done, v21
       http://blofs.herokuapp.com deployed to Heroku

To git@heroku.com:blofs.git
   32e51a2..37d989c  master -> master

这里是从推日志：

2013-04-23T22:28:06.650049+00:00 heroku[slugc]: Slug compilation started
2013-04-23T22:29:11.194613+00:00 heroku[api]: Release v21 created by callum.locke@gmail.com
2013-04-23T22:29:11.365908+00:00 heroku[api]: Deploy 37d989c by callum.locke@gmail.com
2013-04-23T22:29:11.441066+00:00 heroku[web.1]: State changed from up to starting
2013-04-23T22:29:11.932952+00:00 heroku[slugc]: Slug compilation finished
2013-04-23T22:29:12.858139+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2013-04-23T22:29:13.194707+00:00 app[web.1]: I, [2013-04-23T22:29:13.194495 #2]  INFO -- : reaped #<Process::Status: pid 5 exit 0> worker=0
2013-04-23T22:29:13.194902+00:00 app[web.1]: I, [2013-04-23T22:29:13.194747 #2]  INFO -- : master complete
2013-04-23T22:29:14.312014+00:00 heroku[web.1]: Process exited with status 0
2013-04-23T22:29:14.338943+00:00 heroku[web.1]: Starting process with command `bundle exec unicorn -p 25281 -E $RACK_ENV`
2013-04-23T22:29:15.717687+00:00 app[web.1]: I, [2013-04-23T22:29:15.717387 #2]  INFO -- : listening on addr=0.0.0.0:25281 fd=7
2013-04-23T22:29:15.717916+00:00 app[web.1]: I, [2013-04-23T22:29:15.717861 #2]  INFO -- : worker=0 spawning...
2013-04-23T22:29:15.721526+00:00 app[web.1]: I, [2013-04-23T22:29:15.721385 #2]  INFO -- : master process ready
2013-04-23T22:29:15.723623+00:00 app[web.1]: I, [2013-04-23T22:29:15.723389 #5]  INFO -- : worker=0 spawned pid=5
2013-04-23T22:29:15.723805+00:00 app[web.1]: I, [2013-04-23T22:29:15.723750 #5]  INFO -- : Refreshing Gem list
2013-04-23T22:29:16.305653+00:00 heroku[web.1]: State changed from starting to up
2013-04-23T22:29:16.891063+00:00 app[web.1]: I, [2013-04-23T22:29:16.890882 #5]  INFO -- : worker=0 ready

在那之后，我试图加载网页在我的浏览器，而这些是仅有的两个额外的线路中出现的日志：

2013-04-23T22:29:26.685651+00:00 heroku[router]: at=info method=GET path=/ host=blofs.herokuapp.com fwd="46.65.16.44" dyno=web.1 connect=2ms service=156ms status=500 bytes=706
2013-04-23T22:29:26.973073+00:00 heroku[router]: at=info method=GET path=/favicon.ico host=blofs.herokuapp.com fwd="46.65.16.44" dyno=web.1 connect=1ms service=5ms status=200 bytes=0

没有人有任何想法的问题可能是什么？

其他的事情，可能是相关的：

我已经禁用了标准的Heroku Postgres的插件和现在用的是MySQL的ClearDB插件代替。
我已经试过手动更改DATABASE_URL从以前的值（这仍然是Postgres的URL即使我删除了Postgres的插件），以相同的值作为环境变量CLEARDB_DATABASE_URL VAR（MySQL的一个）。这似乎没有任何区别。
我已经加入ruby '2.0.0'我的Gemfile，并添加mysql2和unicorn宝石。而且我用config/unicorn.rb建议在https://devcenter.heroku.com/articles/rails-unicorn
我Procfile只包含： web: bundle exec unicorn -p $PORT -E $RACK_ENV
它正常工作与当地foreman start 。
除了上述修改，它基本上与创建一个彻头彻尾的现成应用程序rails new 。

Answer 1: