This tutorial shows you how build a simple Ruby application with CockroachDB and ActiveRecord. CockroachDB provides an ActiveRecord adapter for CockroachDB as a RubyGem.
For a more realistic use of ActiveRecord with CockroachDB in a Rails app, see our examples-orms repository.
Before you begin
- Install CockroachDB.
- Start up a secure or insecure local cluster.
- Choose the instructions that correspond to whether your cluster is secure or insecure:
Step 1. Install PostgreSQL
pg and activerecord are both dependencies of activerecord-cockroachdb-adapter. Both libraries require a PostgreSQL installation.
To install PostgreSQL from source code, follow the instructions on their documentation website.
You can also use a package manager to install PostgreSQL. For example, to install PostgreSQL on macOS, run the following command:
$ brew install postgresql
To install PostgreSQL on a Debian-based Linux distribution (e.g., Ubuntu), run the following command:
$ apt-get install postgresql
Step 2. Create the maxroach user and bank database
Start the built-in SQL shell:
$ cockroach sql --certs-dir=certs
In the SQL shell, issue the following statements to create the maxroach user and bank database:
> CREATE USER IF NOT EXISTS maxroach;
> CREATE DATABASE bank;
Give the maxroach user the necessary permissions:
> GRANT ALL ON DATABASE bank TO maxroach;
Exit the SQL shell:
> \q
Step 3. Generate a certificate for the maxroach user
Create a certificate and key for the maxroach user by running the following command. The code samples will run as this user.
$ cockroach cert create-client maxroach --certs-dir=certs --ca-key=my-safe-directory/ca.key
Step 4. Run the Ruby code
The following code uses ActiveRecord to map Ruby-specific objects to SQL operations. Specifically, Schema.new.change() creates an accounts table based on the Account model (or drops and recreates the table if it already exists), Account.create() inserts rows into the table, and Account.all selects from the table so that balances can be printed.
Copy the code or download it directly.
# Use bundler inline - these would typically go in a Gemfile
require 'bundler/inline'
gemfile do
source 'https://rubygems.org'
gem 'pg'
gem 'activerecord', '5.2.0'
# CockroachDB ActiveRecord adapter dependency
gem 'activerecord-cockroachdb-adapter', '5.2.0'
end
require 'pg'
require 'active_record'
require 'activerecord-cockroachdb-adapter'
# Connect to CockroachDB using ActiveRecord.
# In Rails, this configuration would go in config/database.yml as usual.
ActiveRecord::Base.establish_connection(
# Specify the CockroachDB ActiveRecord adapter
adapter: 'cockroachdb',
username: 'maxroach',
database: 'bank',
host: 'localhost',
port: 26257,
sslmode: 'require',
# These are the certificate files created in the previous step
sslrootcert: 'certs/ca.crt',
sslkey: 'certs/client.maxroach.key',
sslcert: 'certs/client.maxroach.crt'
)
# Define the Account model.
# In Rails, this would go in app/models/ as usual.
class Account < ActiveRecord::Base
validates :balance, presence: true
end
# Define a migration for the accounts table.
# In Rails, this would go in db/migrate/ as usual.
class Schema < ActiveRecord::Migration[5.0]
def change
create_table :accounts, force: true do |t|
t.integer :balance
end
end
end
# Run the schema migration programmatically.
# In Rails, this would be done via rake db:migrate as usual.
Schema.new.change()
# Create two accounts, inserting two rows into the accounts table.
Account.create!(id: 1, balance: 1000)
Account.create!(id: 2, balance: 250)
# Retrieve accounts and print out the balances
Account.all.each do |acct|
puts "account: #{acct.id} balance: #{acct.balance}"
end
Then run the code:
$ ruby activerecord-basic-sample.rb
The output should be:
-- create_table(:accounts, {:force=>true, :id=>:integer})
-> 0.0883s
account: 1 balance: 1000
account: 2 balance: 250
To verify that the table and rows were created successfully, start the built-in SQL client:
$ cockroach sql --certs-dir=certs --database=bank
Then, issue the following statement:
> SELECT id, balance FROM accounts;
id | balance
-----+----------
1 | 1000
2 | 250
(2 rows)
Step 2. Create the maxroach user and bank database
Start the built-in SQL shell:
$ cockroach sql --insecure
In the SQL shell, issue the following statements to create the maxroach user and bank database:
> CREATE USER IF NOT EXISTS maxroach;
> CREATE DATABASE bank;
Give the maxroach user the necessary permissions:
> GRANT ALL ON DATABASE bank TO maxroach;
Exit the SQL shell:
> \q
Step 3. Run the Ruby code
The following code uses ActiveRecord to map Ruby-specific objects to database tables. Specifically, Schema.new.change() creates an accounts table based on the Account model (or drops and recreates the table if it already exists), Account.create() inserts rows into the table, and Account.all selects from the table so that balances can be printed.
Copy the code or download it directly.
# Use bundler inline - these would typically go in a Gemfile
require 'bundler/inline'
gemfile do
source 'https://rubygems.org'
gem 'pg'
gem 'activerecord', '5.2.0'
# CockroachDB ActiveRecord adapter dependency
gem 'activerecord-cockroachdb-adapter', '5.2.0'
end
require 'pg'
require 'active_record'
require 'activerecord-cockroachdb-adapter'
# Connect to CockroachDB using ActiveRecord.
# In Rails, this configuration would go in config/database.yml as usual.
ActiveRecord::Base.establish_connection(
# Specify the CockroachDB ActiveRecord adapter
adapter: 'cockroachdb',
username: 'maxroach',
database: 'bank',
host: 'localhost',
port: 26257,
sslmode: 'disable'
)
# Define the Account model.
# In Rails, this would go in app/models/ as usual.
class Account < ActiveRecord::Base
validates :balance, presence: true
end
# Define a migration for the accounts table.
# In Rails, this would go in db/migrate/ as usual.
class Schema < ActiveRecord::Migration[5.0]
def change
create_table :accounts, force: true do |t|
t.integer :balance
end
end
end
# Run the schema migration programmatically.
# In Rails, this would be done via rake db:migrate as usual.
Schema.new.change()
# Create two accounts, inserting two rows into the accounts table.
Account.create!(id: 1, balance: 1000)
Account.create!(id: 2, balance: 250)
# Retrieve accounts and print out the balances
Account.all.each do |acct|
puts "account: #{acct.id} balance: #{acct.balance}"
end
Then run the code (no need to run bundler first):
$ ruby activerecord-basic-sample.rb
The output should be:
-- create_table(:accounts, {:force=>true, :id=>:integer})
-> 0.0883s
account: 1 balance: 1000
account: 2 balance: 250
To verify that the table and rows were created successfully, start the built-in SQL client:
$ cockroach sql --insecure --database=bank
Then, issue the following statement:
> SELECT id, balance FROM accounts;
id | balance
-----+----------
1 | 1000
2 | 250
(2 rows)
What's next?
Read more about using ActiveRecord, or check out a more realistic implementation of ActiveRecord with CockroachDB in a Rails app in our examples-orms repository.
You might also be interested in the following pages:
- Client Connection Parameters
- Data Replication
- Fault Tolerance & Recovery
- Replication & Rebalancing
- Cross-Cloud Migration
- Automated Operations
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