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Module: ActiveRecord::ConnectionHandling

Constant Summary

Instance Attribute Summary

Instance Method Summary

Instance Attribute Details

#connected? ⇒ Boolean (readonly)

Returns true if Active Record is connected.

[ GitHub ] 

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 331



def connected?
  connection_handler.connected?(connection_specification_name, role: current_role, shard: current_shard)
end


  








  

    #connection_specification_name   (rw)
  



  

    

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


  



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# File 'activerecord/lib/active_record/connection_handling.rb', line 289



def connection_specification_name
  if !defined?(@connection_specification_name) || @connection_specification_name.nil?
    return self == Base ? Base.name : superclass.connection_specification_name
  end
  @connection_specification_name
end


  








  

    #connection_specification_name=(value)   (rw)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 286



attr_writer :connection_specification_name


  







Instance Method Details



  

    #clear_active_connections!  
  

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# File 'activerecord/lib/active_record/connection_handling.rb', line 351



delegate :clear_active_connections!, :clear_reloadable_connections!,
  :clear_all_connections!, :flush_idle_connections!, to: :connection_handler


  








  

    #clear_all_connections!  
  

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# File 'activerecord/lib/active_record/connection_handling.rb', line 351



delegate :clear_active_connections!, :clear_reloadable_connections!,
  :clear_all_connections!, :flush_idle_connections!, to: :connection_handler


  








  

    #clear_query_caches_for_current_thread  
  



  

    

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


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 269



def clear_query_caches_for_current_thread
  if ActiveRecord::Base.legacy_connection_handling
    ActiveRecord::Base.connection_handlers.each_value do |handler|
      clear_on_handler(handler)
    end
  else
    clear_on_handler(ActiveRecord::Base.connection_handler)
  end
end


  








  

    #clear_reloadable_connections!  
  

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# File 'activerecord/lib/active_record/connection_handling.rb', line 351



delegate :clear_active_connections!, :clear_reloadable_connections!,
  :clear_all_connections!, :flush_idle_connections!, to: :connection_handler


  








  

    #connected_to(database: nil, role: nil, shard: nil, prevent_writes: false, &blk)  
  



  

    

Connects to a role (ex writing, reading or a custom role) and/or shard for the duration of the block. At the end of the block the connection will be returned to the original role / shard.



If only a role is passed, Active Record will look up the connection based on the requested role. If a non-established role is requested an ConnectionNotEstablished error will be raised:



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



When swapping to a shard, the role must be passed as well. If a non-existent shard is passed, an ConnectionNotEstablished error will be raised.



When a shard and role is passed, Active Record will first lookup the role, and then look up the connection by shard key.



ActiveRecord::Base.connected_to(role: :reading, shard: :shard_one_replica) do
  Dog.first # finds first Dog record stored on the shard one replica
end



The database kwarg is deprecated and will be removed in ::Rails 7.0.0 without replacement.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 139



def connected_to(database: nil, role: nil, shard: nil, prevent_writes: false, &blk)
  if legacy_connection_handling
    if self != Base
      raise NotImplementedError, "`connected_to` can only be called on ActiveRecord::Base with legacy connection handling."
    end
  else
    if self != Base && !abstract_class
      raise NotImplementedError, "calling `connected_to` is only allowed on ActiveRecord::Base or abstract classes."
    end

    if name != connection_specification_name && !primary_class?
      raise NotImplementedError, "calling `connected_to` is only allowed on the abstract class that established the connection."
    end
  end

  if database && (role || shard)
    raise ArgumentError, "`connected_to` cannot accept a `database` argument with any other arguments."
  elsif database
    ActiveSupport::Deprecation.warn("The database key in `connected_to` is deprecated. It will be removed in Rails 7.0.0 without replacement.")

    if database.is_a?(Hash)
      role, database = database.first
      role = role.to_sym
    end

    db_config, owner_name = resolve_config_for_connection(database)
    handler = lookup_connection_handler(role)

    handler.establish_connection(db_config, owner_name: owner_name, role: role)

    with_handler(role, &blk)
  elsif role || shard
    unless role
      raise ArgumentError, "`connected_to` cannot accept a `shard` argument without a `role`."
    end

    with_role_and_shard(role, shard, prevent_writes, &blk)
  else
    raise ArgumentError, "must provide a `shard` and/or `role`."
  end
end


  








  

    #connected_to?(role:, shard: ActiveRecord::Base.default_shard)  ⇒ Boolean 
  



  

    

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


  





  


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# File 'activerecord/lib/active_record/connection_handling.rb', line 255



def connected_to?(role:, shard: ActiveRecord::Base.default_shard)
  current_role == role.to_sym && current_shard == shard.to_sym
end


  








  

    #connected_to_many(*classes, role:, shard: nil, prevent_writes: false)  
  



  

    

Connects a role and/or shard to the provided connection names. Optionally prevent_writes can be passed to block writes on a connection. reading will automatically set prevent_writes to true.



connected_to_many is an alternative to deeply nested #connected_to blocks.



Usage:



ActiveRecord::Base.connected_to_many(AnimalsRecord, MealsRecord, role: :reading) do
  Dog.first # Read from animals replica
  Dinner.first # Read from meals replica
  Person.first # Read from primary writer
end


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 194



def connected_to_many(*classes, role:, shard: nil, prevent_writes: false)
  classes = classes.flatten

  if legacy_connection_handling
    raise NotImplementedError, "connected_to_many is not available with legacy connection handling"
  end

  if self != Base || classes.include?(Base)
    raise NotImplementedError, "connected_to_many can only be called on ActiveRecord::Base."
  end

  prevent_writes = true if role == reading_role

  connected_to_stack << { role: role, shard: shard, prevent_writes: prevent_writes, klasses: classes }
  yield
ensure
  connected_to_stack.pop
end


  








  

    #connecting_to(role: default_role, shard: default_shard, prevent_writes: false)  
  



  

    

Use a specified connection.



This method is useful for ensuring that a specific connection is being used. For example, when booting a console in readonly mode.



It is not recommended to use this method in a request since it does not yield to a block like #connected_to.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 220



def connecting_to(role: default_role, shard: default_shard, prevent_writes: false)
  if legacy_connection_handling
    raise NotImplementedError, "`connecting_to` is not available with `legacy_connection_handling`."
  end

  prevent_writes = true if role == reading_role

  self.connected_to_stack << { role: role, shard: shard, prevent_writes: prevent_writes, klasses: [self] }
end


  








  

    #connection  
  



  

    

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.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 282



def connection
  retrieve_connection
end


  








  

    #connection_config  
  



  

    
Deprecated. 


Use connection_db_config instead





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.


  



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# File 'activerecord/lib/active_record/connection_handling.rb', line 306



def connection_config
  connection_pool.db_config.configuration_hash
end


  








  

    #connection_db_config  
  



  

    

Returns the db_config object from the associated connection:



ActiveRecord::Base.connection_db_config
  #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbded10 @env_name="development",
    @name="primary", @config={pool: 5, timeout: 5000, database: "db/development.sqlite3", adapter: "sqlite3"}>



Use only for reading.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 318



def connection_db_config
  connection_pool.db_config
end


  








  

    #connection_pool  
  

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# File 'activerecord/lib/active_record/connection_handling.rb', line 322



def connection_pool
  connection_handler.retrieve_connection_pool(connection_specification_name, role: current_role, shard: current_shard) || raise(ConnectionNotEstablished)
end


  








  

    #connects_to(database: {}, shards: {})  
  



  

    

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



connects_to also supports horizontal sharding. The horizontal sharding API also supports read replicas. Connect a model to a list of shards like this:



class AnimalsModel < ApplicationRecord
  self.abstract_class = true

  connects_to shards: {
    default: { writing: :primary, reading: :primary_replica },
    shard_two: { writing: :primary_shard_two, reading: :primary_shard_replica_two }
  }
end



Returns an array of database connections.


  





  
Raises:


    
  
  • 
    (NotImplementedError)
  
    • 





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 81



def connects_to(database: {}, shards: {})
  raise NotImplementedError, "`connects_to` can only be called on ActiveRecord::Base or abstract classes" unless self == Base || abstract_class?

  if database.present? && shards.present?
    raise ArgumentError, "`connects_to` can only accept a `database` or `shards` argument, but not both arguments."
  end

  connections = []

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

    self.connection_class = true
    connections << handler.establish_connection(db_config, owner_name: owner_name, role: role)
  end

  shards.each do |shard, database_keys|
    database_keys.each do |role, database_key|
      db_config, owner_name = resolve_config_for_connection(database_key)
      handler = lookup_connection_handler(role.to_sym)

      self.connection_class = true
      connections << handler.establish_connection(db_config, owner_name: owner_name, role: role, shard: shard.to_sym)
    end
  end

  connections
end


  








  

    #establish_connection(config_or_env = nil)  
  



  

    

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.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 49



def establish_connection(config_or_env = nil)
  config_or_env ||= DEFAULT_ENV.call.to_sym
  db_config, owner_name = resolve_config_for_connection(config_or_env)
  connection_handler.establish_connection(db_config, owner_name: owner_name, role: current_role, shard: current_shard)
end


  








  

    #flush_idle_connections!  
  

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# File 'activerecord/lib/active_record/connection_handling.rb', line 351



delegate :clear_active_connections!, :clear_reloadable_connections!,
  :clear_all_connections!, :flush_idle_connections!, to: :connection_handler


  








  

    #remove_connection(name = nil)  
  

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# File 'activerecord/lib/active_record/connection_handling.rb', line 335



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, role: current_role, shard: current_shard)
    self.connection_specification_name = nil
  end

  connection_handler.remove_connection_pool(name, role: current_role, shard: current_shard)
end


  








  

    #retrieve_connection  
  

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# File 'activerecord/lib/active_record/connection_handling.rb', line 326



def retrieve_connection
  connection_handler.retrieve_connection(connection_specification_name, role: current_role, shard: current_shard)
end


  








  

    #while_preventing_writes(enabled = true, &block)  
  



  

    

Prevent writing to the database regardless of role.



In some cases you may want to prevent writes to the database even if you are on a database that can write. while_preventing_writes will prevent writes to the database for the duration of the block.



This method does not provide the same protection as a readonly user and is meant to be a safeguard against accidental writes.



See READ_QUERY for the queries that are blocked by this method.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_handling.rb', line 241



def while_preventing_writes(enabled = true, &block)
  if legacy_connection_handling
    connection_handler.while_preventing_writes(enabled, &block)
  else
    connected_to(role: current_role, prevent_writes: enabled, &block)
  end
end