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Fail to setup database_cleaner for dual database

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#419 2 commenti 0 reazioni 0 assegnatari Vedi su GitHub

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Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
35/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Ferma
Stack tecnologico
postgresql, rails, ruby
Ambito
databases, testing

Direzione di ricerca

Inizia in lib/database_cleaner/active_record/base.rb, soprattutto con connection_class, lookup_from_connection_pool ed establish_connection. Riproduci i due avvii di DatabaseCleaner con le connessioni test e secondary_test, quindi aggiungi una copertura di regressione che dimostri che Device e User mantengono le connessioni corrette senza che ActiveRecord::Base.establish_connection influisca su tutti i discendenti.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

I have two database, one with a model call Device, and the other has a model call User.

When I set up database_cleaner according to readme describe:

  config.use_transactional_fixtures = false
  config.before(:suite) do
    DatabaseCleaner[:active_record,{:connection => :test}].strategy  = :transaction
    DatabaseCleaner[:active_record,{:connection => :secondary_test}].strategy = :transaction
  end

  config.before(:each) do
    DatabaseCleaner.start
  end

  config.after(:each) do
    DatabaseCleaner.clean
  end

I found that in my test, device model's connection will point to secondary_test database. And I will have following error as my secondary_test database don't have a table call devices:

ActiveRecord::StatementInvalid:
  PG::UndefinedTable: ERROR:  relation "devices" does not exist
  LINE 5:                WHERE a.attrelid = '"devices"'::regclass
                                            ^
  :               SELECT a.attname, format_type(a.atttypid, a.atttypmod),
                       pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod
                  FROM pg_attribute a LEFT JOIN pg_attrdef d
                    ON a.attrelid = d.adrelid AND a.attnum = d.adnum
                 WHERE a.attrelid = '"devices"'::regclass
                   AND a.attnum > 0 AND NOT a.attisdropped
                 ORDER BY a.attnum

I dig in the code, and found that it is cause by #connection_class

      def connection_class
        @connection_class ||= if db && !db.is_a?(Symbol)
                                db
                              elsif connection_hash
                                lookup_from_connection_pool || establish_connection
                              else
                                ::ActiveRecord::Base
                              end
      end

      private

      def lookup_from_connection_pool
        if ::ActiveRecord::Base.respond_to?(:descendants)
          database_name = connection_hash["database"] || connection_hash[:database]
          models        = ::ActiveRecord::Base.descendants
          models.detect { |m| m.connection_pool.spec.config[:database] == database_name }
        end
      end

      def establish_connection
        ::ActiveRecord::Base.establish_connection(connection_hash)
      end

However, since ::ActiveRecord::Base.descendants is blank when lookup_from_connection_pool is called, lookup_from_connection_pool would return nil, and establish_connection will be called. Unfortunately, ActiveRecord::Base.establish_connection(connection_hash) has a huge side effect in Rails 4+. It will set connection to specify one for ALL models that inherit from ActiveRecord::Base class. This can be reproduced by following code:

ActiveRecord::Base.establish_connection('test')
Device.connection

In my case, following code:

DatabaseCleaner[:active_record,{:connection => :test}].start
DatabaseCleaner[:active_record,{:connection => :secondary_test}].start

will first set ALL ActiveRecord::Base descendants' connections to test db, then it will set ALL their connection to secondary_test. Therefore, when I try to use Device in my spec, I will have PG::UndefinedTable: ERROR

Here is the similar issues that cause by the side effect for establish_connection:

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