Class: Rails::Sharding::ConnectionHandler

Inherits:
Object
  • Object
show all
Defined in:
lib/rails/sharding/connection_handler.rb

Class Method Summary collapse

Class Method Details

.connected?(shard_group, shard_name) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rails/sharding/connection_handler.rb', line 76

def self.connected?(shard_group, shard_name)
  connection_handler.connected?(connection_name(shard_group, shard_name))
end

.connection_pool(shard_group, shard_name) ⇒ Object

Raises:

  • (ActiveRecord::ConnectionNotEstablished) 


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# File 'lib/rails/sharding/connection_handler.rb', line 55

def self.connection_pool(shard_group, shard_name)
  if connection_pool = connection_handler.retrieve_connection_pool(connection_name(shard_group, shard_name))
    return connection_pool
  end

  # mimicking behavior of rails at:
  # https://github.com/rails/rails/blob/v5.0.0.1/activerecord/lib/active_record/connection_handling.rb#124
  raise ActiveRecord::ConnectionNotEstablished, "No connection pool for shard #{connection_name(shard_group, shard_name)}" if connection_pool.nil?
end

.establish_all_connections ⇒ Object

Establishes connections to all shards in all shard groups. Despite the name, this actually only creates a connection pool with zero connections for each shard. The connections will be allocated for each thread when #retrieve_connection or #with_connection are called



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# File 'lib/rails/sharding/connection_handler.rb', line 8

def self.establish_all_connections
  Core.shard_groups.each do |shard_group|
    Core.shard_names(shard_group).each do |shard_name|
      establish_connection(shard_group, shard_name)
    end
  end
end

.establish_connection(shard_group, shard_name, environment = nil) ⇒ Object

Establishes a connection to a single shard in a single shard group



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# File 'lib/rails/sharding/connection_handler.rb', line 17

def self.establish_connection(shard_group, shard_name, environment=nil)
  self.setup unless defined? @@connection_handler

  configurations = (environment.nil? ? Core.configurations : Core.configurations(environment))

  shard_group_configurations = configurations[shard_group.to_s]
  if shard_group_configurations.nil?
    raise Errors::ConfigNotFoundError, "Cannot find configuration for shard_group '#{shard_group}' in environment '#{environment}' in #{Config.shards_config_file}"
  end

  resolver = ActiveRecord::ConnectionAdapters::ConnectionSpecification::Resolver.new(shard_group_configurations)
  begin
    connection_spec = resolver.spec(shard_name.to_sym)

    # since Rails 5.1 connection_spec already comes with :name set to whatever
    # key you used to retrieve it from the resolver, in this case the shard_name.
    # We don't want that, so we overwrite it with our connection name formed
    # by shard_group:shard_name
    connection_name = connection_name(shard_group, shard_name)
    connection_spec.instance_variable_set(:@name, connection_name)
  rescue ActiveRecord::AdapterNotSpecified
    raise Errors::ConfigNotFoundError, "Cannot find configuration for shard '#{shard_group}:#{shard_name}' in environment '#{environment}' in #{Config.shards_config_file}, or it does not specify :adapter"
  end

  # Since Rails 5.1 we cannot use connection_handler.establish_connection anymore,
  # because it does more than establishing_connection. It does a second
  # connection specification lookup on Base.configurations (where our spec
  # is not, because we define it in a shards.yml instead of the regular
  # database.yml) and it notifies subscribers of a event that does not concern
  # us. Because of this we directly create the connection_pool and inject to
  # the handler.
  # Note: we should consider writting our connection handler from scratch, since
  # it has become simpler than reusing the one from rails. And it will not break
  # as long as the ConnectionPool interface is stable.
  connection_handler.remove_connection(connection_spec.name)
  connection_handler.send(:owner_to_pool)[connection_spec.name] = ActiveRecord::ConnectionAdapters::ConnectionPool.new(connection_spec)
end

.remove_connection(shard_group, shard_name) ⇒ Object 



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# File 'lib/rails/sharding/connection_handler.rb', line 90

def self.remove_connection(shard_group, shard_name)
  connection_handler.remove_connection(connection_name(shard_group, shard_name))
end

.retrieve_connection(shard_group, shard_name) ⇒ Object 



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# File 'lib/rails/sharding/connection_handler.rb', line 65

def self.retrieve_connection(shard_group, shard_name)
  connection_name = connection_name(shard_group, shard_name)
  connection = connection_handler.retrieve_connection(connection_name)

  if connection && Config.add_shard_tag_to_query_logs
    add_shard_tag_to_connection_log(connection, connection_name)
  else
    connection
  end
end

.with_connection(shard_group, shard_name, &block) ⇒ Object 



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# File 'lib/rails/sharding/connection_handler.rb', line 80

def self.with_connection(shard_group, shard_name, &block)
  connection_pool(shard_group, shard_name).with_connection do |connection|
    if connection && Config.add_shard_tag_to_query_logs
      connection_name = connection_name(shard_group, shard_name)
      add_shard_tag_to_connection_log(connection, connection_name)
    end
    block.call(connection)
  end
end