module ActiveRecord::ConnectionHandling

Constants

DEFAULT_ENV
RAILS_ENV

Attributes

connection_specification_name[W]

Public Instance Methods

clear_query_caches_for_current_thread() click to toggle source

Clears the query cache for all connections associated with the current thread.

# File lib/active_record/connection_handling.rb, line 176
def clear_query_caches_for_current_thread
  ActiveRecord::Base.connection_handlers.each_value do |handler|
    handler.connection_pool_list.each do |pool|
      pool.connection.clear_query_cache if pool.active_connection?
    end
  end
end
connected?() click to toggle source

Returns true if Active Record is connected.

# File lib/active_record/connection_handling.rb, line 224
def connected?
  connection_handler.connected?(connection_specification_name)
end
connected_to(database: nil, role: nil, prevent_writes: false, &blk) click to toggle source

Connects to a database or role (ex writing, reading, or another custom role) for the duration of the block.

If a role is passed, Active Record will look up the connection based on the requested role:

ActiveRecord::Base.connected_to(role: :writing) do
  Dog.create! # creates dog using dog writing connection
end

ActiveRecord::Base.connected_to(role: :reading) do
  Dog.create! # throws exception because we're on a replica
end

ActiveRecord::Base.connected_to(role: :unknown_role) do
  # raises exception due to non-existent role
end

The `database` kwarg is deprecated in 6.1 and will be removed in 6.2

It is not recommended for use as it re-establishes a connection every time it is called.

# File lib/active_record/connection_handling.rb, line 102
def connected_to(database: nil, role: nil, prevent_writes: false, &blk)
  if database && role
    raise ArgumentError, "connected_to can only accept a `database` or a `role` argument, but not both arguments."
  elsif database
    if database.is_a?(Hash)
      role, database = database.first
      role = role.to_sym
    end

    config_hash = resolve_config_for_connection(database)
    handler = lookup_connection_handler(role)

    handler.establish_connection(config_hash)

    with_handler(role, &blk)
  elsif role
    prevent_writes = true if role == reading_role

    with_handler(role.to_sym) do
      connection_handler.while_preventing_writes(prevent_writes, &blk)
    end
  else
    raise ArgumentError, "must provide a `database` or a `role`."
  end
end
connected_to?(role:) click to toggle source

Returns true if role is the current connected role.

ActiveRecord::Base.connected_to(role: :writing) do
  ActiveRecord::Base.connected_to?(role: :writing) #=> true
  ActiveRecord::Base.connected_to?(role: :reading) #=> false
end
# File lib/active_record/connection_handling.rb, line 134
def connected_to?(role:)
  current_role == role.to_sym
end
connection() click to toggle source

Returns the connection currently associated with the class. This can also be used to “borrow” the connection to do database work unrelated to any of the specific Active Records.

# File lib/active_record/connection_handling.rb, line 187
def connection
  retrieve_connection
end
connection_config() click to toggle source

Returns the configuration of the associated connection as a hash:

ActiveRecord::Base.connection_config
# => {pool: 5, timeout: 5000, database: "db/development.sqlite3", adapter: "sqlite3"}

Please use only for reading.

# File lib/active_record/connection_handling.rb, line 211
def connection_config
  connection_pool.spec.config
end
connection_pool() click to toggle source
# File lib/active_record/connection_handling.rb, line 215
def connection_pool
  connection_handler.retrieve_connection_pool(connection_specification_name) || raise(ConnectionNotEstablished)
end
connection_specification_name() click to toggle source

Return the specification name from the current class or its parent.

# File lib/active_record/connection_handling.rb, line 194
def connection_specification_name
  if !defined?(@connection_specification_name) || @connection_specification_name.nil?
    return self == Base ? "primary" : superclass.connection_specification_name
  end
  @connection_specification_name
end
connects_to(database: {}) click to toggle source

Connects a model to the databases specified. The database keyword takes a hash consisting of a role and a database_key.

This will create a connection handler for switching between connections, look up the config hash using the database_key and finally establishes a connection to that config.

class AnimalsModel < ApplicationRecord
  self.abstract_class = true

  connects_to database: { writing: :primary, reading: :primary_replica }
end

Returns an array of established connections.

# File lib/active_record/connection_handling.rb, line 67
def connects_to(database: {})
  connections = []

  database.each do |role, database_key|
    config_hash = resolve_config_for_connection(database_key)
    handler = lookup_connection_handler(role.to_sym)

    connections << handler.establish_connection(config_hash)
  end

  connections
end
current_role() click to toggle source

Returns the symbol representing the current connected role.

ActiveRecord::Base.connected_to(role: :writing) do
  ActiveRecord::Base.current_role #=> :writing
end

ActiveRecord::Base.connected_to(role: :reading) do
  ActiveRecord::Base.current_role #=> :reading
end
# File lib/active_record/connection_handling.rb, line 147
def current_role
  connection_handlers.key(connection_handler)
end
establish_connection(config_or_env = nil) click to toggle source

Establishes the connection to the database. Accepts a hash as input where the :adapter key must be specified with the name of a database adapter (in lower-case) example for regular databases (MySQL, PostgreSQL, etc):

ActiveRecord::Base.establish_connection(
  adapter:  "mysql2",
  host:     "localhost",
  username: "myuser",
  password: "mypass",
  database: "somedatabase"
)

Example for SQLite database:

ActiveRecord::Base.establish_connection(
  adapter:  "sqlite3",
  database: "path/to/dbfile"
)

Also accepts keys as strings (for parsing from YAML for example):

ActiveRecord::Base.establish_connection(
  "adapter"  => "sqlite3",
  "database" => "path/to/dbfile"
)

Or a URL:

ActiveRecord::Base.establish_connection(
  "postgres://myuser:mypass@localhost/somedatabase"
)

In case ActiveRecord::Base.configurations is set (Rails automatically loads the contents of config/database.yml into it), a symbol can also be given as argument, representing a key in the configuration hash:

ActiveRecord::Base.establish_connection(:production)

The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError may be returned on an error.

# File lib/active_record/connection_handling.rb, line 48
def establish_connection(config_or_env = nil)
  config_hash = resolve_config_for_connection(config_or_env)
  connection_handler.establish_connection(config_hash)
end
remove_connection(name = nil) click to toggle source
# File lib/active_record/connection_handling.rb, line 228
def remove_connection(name = nil)
  name ||= @connection_specification_name if defined?(@connection_specification_name)
  # if removing a connection that has a pool, we reset the
  # connection_specification_name so it will use the parent
  # pool.
  if connection_handler.retrieve_connection_pool(name)
    self.connection_specification_name = nil
  end

  connection_handler.remove_connection(name)
end
retrieve_connection() click to toggle source
# File lib/active_record/connection_handling.rb, line 219
def retrieve_connection
  connection_handler.retrieve_connection(connection_specification_name)
end