Rails: No connection pool for ActiveRecord::Base

Question

I'm trying to use rails 4.2.6 to develop an app. I'm trying to use postgres for database. Server starts fine but when I try loading a page it throws this "No connection pool for ActiveRecord::Base" error.

What could it be?

EDIT

The pg gem wasn't working properly. I had to comment it before starting the server and then uncomment it from my GemFile afterwards. I realized that I was using Ruby 2.3 instead of Ruby 2.0 (as intended). I removed ruby 2.3 and set up everything under ruby 2.0 environment. It's now working properly.

I had read somewhere that there were some issues with the 'pg' gem in newer Rails releases, requiring people to use 'gem install pg --pre' instead for installing the gem. I tried that, but then my app was requiring the 'pg' gem in my GemFile and, well, the problem stated above showed up again.

This is how my database.yml file ended up:

  default: &default
     adapter: postgresql
     encoding: unicode
     host: localhost
     username: -------
     password: -------
     pool: 5

  development:
     <<: *default
     database: myDbName

I guess you should specify the port (5432 if you haven't changed postgres defaults) — Alexander Gorg
– Alexander Gorg, Commented Nov 6, 2019 at 9:03

golfadas · Accepted Answer · 2017-05-08 12:30:13Z

46

If you are experiencing this error from a rake task, chances are you are not running the :environment task before your task.

Changing:

task :task_name do
end

to:

task task_name: :environment do
end

Should fix the issue.

answered May 8, 2017 at 12:30

golfadas

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3 Comments

Dynamo Over a year ago

In which file do we have to change this?

golfadas Over a year ago

The rake task that is not loading the rails environment

MegaTux Over a year ago

In my case (Roda app, not Rails), was similar, changing Rake::TestTask.new(:test) do |t| to Rake::TestTask.new(name: :test, deps: :environment) do |t|. Hope that helps to others.

Promise Preston · Accepted Answer · 2019-08-11 13:53:05Z

This issue arises when the server cannot find the corresponding database it depends on to pull data from.

I had same issue from my end, I updated my version of Sqlite3, and it was higher than the version that the current Puma Server version supports.

I simply had to uninstall the Sqlite3 version, and then install the version supported by the current version of Puma Server.

gem uninstall sqlite3

This will uninstall the updated version of Sqlite3, and then you run the code below stating the version supported by your current server.

gem install sqlite3

Or you can as well open your Gemfile, and then include the version for the database that you are using

gem 'sqlite3', '~> 1.3.6'

N/B: The sqlite3 version is the most current version as at the time of writing this answer

And then run

bundle update

to install the version of the database that you specified.

That's all.

I hope this helps.

thomasstephn · Accepted Answer · 2016-07-04 03:46:00Z

3

For PostgreSQL your database.yml file should look something like that:

default: &default
  adapter: postgresql
  encoding: unicode
  # For details on connection pooling, see rails configuration guide
  # http://guides.rubyonrails.org/configuring.html#database-pooling
  pool: 5

development:
  <<: *default
  database: your_db_name

Also make sure that you have the gem installed: in your Gemfile:

gem 'pg'

Finally, restart your server.

Hope that helps

Edit: I almost forgot, make sure you have your PostgresSQL running, check this link for download and setup.

answered Jul 4, 2016 at 3:46

thomasstephn

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Comments

M. Karim · Accepted Answer · 2016-07-04 03:29:25Z

2

Check the database.yml if all settings are ok. If its the first time and you didn't create the database yet use this command to create the database

rake db:create

If the database already exists try reset the db migrations,

rake db:migrate:reset

Hope it'll solve the problem. Go to rails console and try something to check if its working or not.

answered Jul 4, 2016 at 3:29

M. Karim

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The Whiz of Oz · Accepted Answer · 2018-10-08 18:32:49Z

2

I had to simply restart the server for the warning to go away.

answered Oct 8, 2018 at 18:32

The Whiz of Oz

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Comments

sathya_dev · Accepted Answer · 2016-07-04 06:48:51Z

0

I've encountered the same problem when I try to access the Model before creating the DataBase.

Make sure you run rake db:migrate at least once.

If you already run migration then check the Database as mentioned in previous answers.

answered Jul 4, 2016 at 6:48

sathya_dev

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user9869932 · Accepted Answer · 2019-11-18 21:01:33Z

0

In my case, the config/database.yml was taking variables from the environment:

# ...
test:
  <<: *default
  database: <%= ENV.fetch("DB_NAME") %>_test
  username: <%= ENV.fetch("DB_USER") %>
  password: <%= ENV.fetch("DB_PASS") %>
# ...

The error was coming when the new terminal window where I was running the bundle exec rails spec did not have those variables initialized.

Doing,

$ export DB_NAME=mydb
$ export DB_USER=myuser
$ export DB_PASS=mypass
$ bundle exec rails spec

fixed the issue.

answered Nov 18, 2019 at 21:01

user9869932

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Fakhriddin Makhmadiyorov · Accepted Answer · 2023-02-09 05:05:09Z

0

I had to restart the server, and make sure you entered username and password. Create development and test databases

answered Feb 9, 2023 at 5:05

Fakhriddin Makhmadiyorov

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Comments

Jared Beck · Accepted Answer · 2024-07-19 17:34:49Z

0

If you encounter this error in a rake task, and you use models in an initializer, and you're not using the latest version of Rails, it could be caused by https://github.com/rails/rails/issues/43059 which was fixed by https://github.com/rails/rails/pull/45450.

If you can't upgrade Rails, you may be able work around the issue by delaying the model operation, by using after_initialize:

# config/initializers/my_initializer_which_uses_models.rb
Rails.application.config.after_initialize do
  # your model-using code
end

I encountered this issue in Rails 6.1.7.8. I'm not sure which versions contain the fix (PR-45450)

answered Jul 19, 2024 at 17:34

Jared Beck

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Anand Raja · Accepted Answer · 2019-02-24 14:29:05Z

-1

when you are running rails db:migrate in data base rows will be created according to your migration files. you can see schema for further info.

answered Feb 24, 2019 at 14:29

Anand Raja

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rodmclaughlin · Accepted Answer · 2016-08-22 00:28:30Z

-2

Rails 5

New app

Using Postgresql for both test and development

Specs run, so Rails can connect to Postgresql

But when I started the web app, I got "No connection pool with id primary found."

Ran 'bin/rails db:migrate:reset' and restarted the app. It worked. No idea why.

database.yml:

    development:
      adapter: postgresql
      encoding: unicode
      database: rails5_development
      pool: 5
      username: foo
      password: bar
      host: localhost
      port: 5432

    test:
      adapter: postgresql
      encoding: unicode
      database: rails5_test
      pool: 5
      username: foo
      password: bar
      host: localhost
      port: 5432

answered Aug 22, 2016 at 0:28

rodmclaughlin

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