Heroku上的Rails 4應用程序是500，但日誌中沒有錯誤消息

Question

我製作了一個新的Rails 4測試版應用程序，並將它部署到Heroku（使用Ruby 2.0.0，並通過Procfile使用Unicorn）。

運行良好局部與foreman start，但是當我訪問了部署應用程序的主頁，我只是得到標準的Heroku 500錯誤：

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

然而，在日誌中，沒有錯誤 。我不知道是什麼原因造成的500

這裏是我最後git push heroku master輸出：

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 

這裏是從推日誌：

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 

之後，我試圖在瀏覽器中加載主頁，這些是日誌中出現的唯一兩條額外的行：

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 

有沒有人有任何想法可能是什麼問題？

其他的事情，可能是相關的：

• 我已禁用標準的Heroku Postgres的插件和現在用的是MySQL的ClearDB插件代替。
• 我試過手動更改DATABASE_URL環境變量從以前的值（即使刪除postgres插件後仍然是postgres URL）到與CLEARDB_DATABASE_URL var（mysql之一）相同的值。這似乎沒有任何區別。
• 我已將ruby '2.0.0'添加到我的Gemfile中，並添加了mysql2和unicorn寶石。我已經使用了config/unicorn.rb在https://devcenter.heroku.com/articles/rails-unicorn
• 我Procfile建議只包含：web: bundle exec unicorn -p $PORT -E $RACK_ENV
• 它正常工作與當地foreman start。
• 除了上述修改之外，它基本上是一個用rails new創建的開箱即用應用程序。

Answer 1

您需要將gem 'rails_12factor'添加到您的Gemfile中。這是一個臨時的修復從Heroku使Rails 4+與他們的服務工作。

請參閱Getting Started with Rails 4.x on Heroku或Getting Started with Rails 5.x on Heroku。

Answer 2

這些答案告訴您如何打開日誌，以便您可以查找錯誤，但並沒有真正回答這個問題：'可能會出錯？

從答覆@Lauren到 this question建議

除此之外，這裏的另一種可能性 - 如果您嘗試訪問ENV不斷在生產環境中，並沒有通過heroku config:set設置，這也將導致一個很沉默的500錯誤。