生产模式下的Rails问题，mysql数据库

Question

App is running smoothly in development mode, but deploying it onto a managed server brings up the public/500.html page ("We're sorry, but something went wrong") , seemingly when content queries the mysql database. Putting up static content works, puzzlingly dynamic content only works locally in dev.

rake db:migrate went properly, I've manually inserted a test entry into the mysql database.

Yet requesting the view results in 500 and the log gives

ActionView::Template::Error (NULL pointer given):
    10:  ...
    11:    <% @projects.each do |project| %>
    12:  ...        

Server runs MySQL 5.1.54, Rails has mysql gem installed. Any hints appreciated!

edit:

So I just started

rails c production

on the remote server and created an entry in my "Client" model:

irb(main):003:0> c = Client.new => #<Client id: nil, name: nil, permalink: nil, created_at: nil, updated_at: nil> irb(main):004:0> c.name = "realclient" => "realclient" irb(main):005:0> c => #<Client id: nil, name: "realclient", permalink: nil, created_at: nil, updated_at: nil> irb(main):006:0> c.save => true

While all fields except for name are displayed empty in irb, the actual DB on the server show all repective fields okay:

2 realclient realclient 2011-04-22 13:59:12 2011-04-22 13:59:12 (id, name, permalink, created, updated)

So bottom line: Active Record cannot receive values correctly from the DB that are actually there?

Answer 1

When you ran rake db:migrate you probably did not have a RAILS_ENV set and so were still running in development environment. Try running:

RAILS_ENV=production rake db:migrate

See if you get an error then, and if so you can re-run it with the --trace option for more detail.

You probably need to debug this issue on your config/database.yml - there'll be something missing or misconfigured in the production section (or maybe you haven't created the DB or something, I'm not familiar with that specific error message).

Answer 2

** Solved **

My hosting provider only allows use of their pre-installed mysql 2.7 gem. Any manual loading of a mysql gem in Gemfile results in Active Record errors – even loading an own 2.7 version on top. Sticking to the default gem on the managed server works.

Setting up a new database individually on the server could probably enable use of custom database gems. So while this was a very specific problem, maybe the answer helps somebody else working with rails on a managed server.