More debugging with deployment

While I was experimenting with the dotenv-heroku gem, the app I was deploying started showing the app crashed error message. I ran all my tests before pushing the code to heroku so I was sure that the problem had something to do with the configuration.

First suspect: Devise secret key

Since I had just extracted the secret key for Devise into an environment variable, I thought that the problem was because the Rails app was throwing an error since Devise couldn’t read the environment variable. I undid my commit but the app still wouldn’t start. I added heroku-repo to see if the problem could be fixed by rebuilding the repository with different keys for the environment variable.

Second suspect: database.yml

I tried to see if I could access the app from the command line. I ran heroku run rails console and received the error:

active_record/connection_adapters/connection_specification.rb:37:in `initialize': undefined method `tr' for nil:NilClass (NoMethodError)

That led me to question if my configuration in the database.yml was wrong or that the yaml file wasn’t properly formatted. I played around with different settings with no luck. After searching through articles and Heroku’s devcenter, I found out that Heroku bypasses that file and only needs the url for the database.

Third suspect: DATABASE_URL

The corresponding method was:

def initialize(url)
  raise "Database URL cannot be empty" if url.blank?
  @uri     = uri_parser.parse(url)
  @adapter = @uri.scheme.tr('-', '_')
  @adapter = "postgresql" if @adapter == "postgres"
  if @uri.opaque
    @uri.opaque, @query = @uri.opaque.split('?', 2)
  else
    @query = @uri.query
  end
end

Since the first line wasn’t raised, the url was not blank. The method was reading the DATABASE_URL variable but was having problems afterwards. Something was happening in the next two lines. The instance variable @uri was calling a method:

def uri_parser
    @uri_parser ||= URI::Parser.new
end

URI::Parser is part of a Ruby standard library that deals with a string of characters representing a uniform resource identifier. The uri_parser method instantiates a new URI object and the parse method then tries to create a uri object from the url passed in. The @adapter tries to read the resulting variable with the scheme method and that was when the tr method throws an error because scheme can’t read the object. After reading the documention for the parse method, I realized that the DATABASE_URL variable that was set in the environment was not properly formatted.

Solution

At some point when I first tried to push the .env file to Heroku, the url changed and the colon characters turned into equal characters. I’m not sure if the dotenv-heroku gem did this but I exchanged the gem for heroku-config instead and set the variables that way.

Easier way to debug

I realized later that above the initialize method was an example comment:

    # == Example
    #
    #   url = "postgresql://foo:bar@localhost:9000/foo_test?pool=5&timeout=3000"
    #   ConnectionUrlResolver.new(url).to_hash
    #   # => {
    #     "adapter"  => "postgresql",
    #     "host"     => "localhost",
    #     "port"     => 9000,
    #     "database" => "foo_test",
    #     "username" => "foo",
    #     "password" => "bar",
    #     "pool"     => "5",
    #     "timeout"  => "3000"
    #   }

If I read the example for the url I would have seen that the DATABASE_URL was not properly formatted. I appreciate that I’m now able to dig into Rails to figure out what’s wrong, but reading the error message and corresponding comments carefully could have saved me hours of time. A lesson learned for the next time I have problems pushing environment variables.

Links

Summary of Ruby Collections This was an interesting article on Ruby collections, which I feel is the type of object that I use the most. Most of it is a refresher but I did learn that Ruby has tuples in one of its libraries and how it could be used.
Intro to Devise This link was also a little bit of a refresher but it’s very thorough and it did go through how to configure the mailer with delayed job. Also, the author is doing a whole series on authentication with Rails and I’m looking forward to the next one.
Rails API tips I’ve been trying to learn more about creating a Rails API that could go with a Javascript frontend and this artcle gave really good tips about problems I didn’t consider. I’m particularly interested in learning about the two Rack middlewares he suggested; rack-cors and heroku-deflator.
Regex This post goes deep into how a regular expression is parsed. The author was explaining how he structured his gem to create regex examples.

Ray's Blog

More Debugging With Deployment