Module: ActiveRecordShards::ConnectionSwitcher

Included in:
ActiveRecord::Base
Defined in:
lib/active_record_shards/connection_switcher.rb,
lib/active_record_shards/connection_switcher-4-2.rb,
lib/active_record_shards/connection_switcher-5-0.rb,
lib/active_record_shards/connection_switcher-5-1.rb,
lib/active_record_shards/connection_switcher-6-0.rb

Defined Under Namespace

Classes: PrimaryReplicaProxy

Constant Summary collapse

SHARD_NAMES_CONFIG_KEY = 
'shard_names'

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.extended(base) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 9

def self.extended(base)
  if ActiveRecord::VERSION::MAJOR >= 5
    base.singleton_class.send(:alias_method, :load_schema_without_default_shard!, :load_schema!)
    base.singleton_class.send(:alias_method, :load_schema!, :load_schema_with_default_shard!)
  else
    base.singleton_class.send(:alias_method, :columns_without_default_shard, :columns)
    base.singleton_class.send(:alias_method, :columns, :columns_with_default_shard)
  end

  base.singleton_class.send(:alias_method, :table_exists_without_default_shard?, :table_exists?)
  base.singleton_class.send(:alias_method, :table_exists?, :table_exists_with_default_shard?)

  base.singleton_class.send(:alias_method, :reset_primary_key_without_default_shard, :reset_primary_key)
  base.singleton_class.send(:alias_method, :reset_primary_key, :reset_primary_key_with_default_shard)
end

Instance Method Details

#connection_pool_name ⇒ Object

Name of the connection pool. Used by ConnectionHandler to retrieve the current connection pool.



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# File 'lib/active_record_shards/connection_switcher-4-2.rb', line 4

def connection_pool_name # :nodoc:
  name = current_shard_selection.shard_name(self)

  # e.g. if "production_replica" is not defined in `Configuration`, fall back to "production"
  if configurations[name].nil? && on_replica?
    current_shard_selection.shard_name(self, false)
  else
    name
  end
end

#connection_specification_name ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher-5-0.rb', line 3

def connection_specification_name
  name = current_shard_selection.resolve_connection_name(sharded: is_sharded?, configurations: configurations)

  unless configurations[name] || name == "primary"
    raise ActiveRecord::AdapterNotSpecified, "No database defined by #{name} in your database config. (configurations: #{configurations.to_h.keys.inspect})"
  end

  name
end

#current_shard_id ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 154

def current_shard_id
  current_shard_selection.shard
end

#current_shard_selection ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 150

def current_shard_selection
  Thread.current[:shard_selection] ||= ShardSelection.new
end

#default_shard=(new_default_shard) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 25

def default_shard=(new_default_shard)
  ActiveRecordShards::ShardSelection.default_shard = new_default_shard
  switch_connection(shard: new_default_shard)
end

#on_all_shards ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 51

def on_all_shards
  old_options = current_shard_selection.options
  if supports_sharding?
    shard_names.map do |shard|
      switch_connection(shard: shard)
      yield(shard)
    end
  else
    [yield]
  end
ensure
  switch_connection(old_options)
end

#on_cx_switch_block(which, force: false, construct_ro_scope: nil, &block) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 118

def on_cx_switch_block(which, force: false, construct_ro_scope: nil, &block)
  @disallow_replica ||= 0
  @disallow_replica += 1 if [:primary, :master].include?(which)

  ActiveRecordShards::Deprecation.warn('the `:master` option should be replaced with `:primary`!') if which == :master

  switch_to_replica = force || @disallow_replica.zero?
  old_options = current_shard_selection.options

  switch_connection(replica: switch_to_replica)

  # we avoid_readonly_scope to prevent some stack overflow problems, like when
  # .columns calls .with_scope which calls .columns and onward, endlessly.
  if self == ActiveRecord::Base || !switch_to_replica || construct_ro_scope == false || ActiveRecordShards.disable_replica_readonly_records == true
    yield
  else
    readonly.scoping(&block)
  end
ensure
  @disallow_replica -= 1 if [:primary, :master].include?(which)
  switch_connection(old_options) if old_options
end

#on_first_shard(&block) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 42

def on_first_shard(&block)
  shard_name = shard_names.first
  on_shard(shard_name, &block)
end

#on_primary(&block) ⇒ Object Also known as: on_master 



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# File 'lib/active_record_shards/connection_switcher.rb', line 108

def on_primary(&block)
  on_primary_or_replica(:primary, &block)
end

#on_primary_db(&block) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 30

def on_primary_db(&block)
  on_shard(nil, &block)
end

#on_primary_if(condition, &block) ⇒ Object Also known as: on_master_if 



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# File 'lib/active_record_shards/connection_switcher.rb', line 75

def on_primary_if(condition, &block)
  condition ? on_primary(&block) : yield
end

#on_primary_or_replica(which, &block) ⇒ Object Also known as: on_master_or_slave 



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# File 'lib/active_record_shards/connection_switcher.rb', line 85

def on_primary_or_replica(which, &block)
  if block_given?
    on_cx_switch_block(which, &block)
  else
    PrimaryReplicaProxy.new(self, which)
  end
end

#on_primary_unless(condition, &block) ⇒ Object Also known as: on_master_unless 



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# File 'lib/active_record_shards/connection_switcher.rb', line 80

def on_primary_unless(condition, &block)
  on_primary_if(!condition, &block)
end

#on_replica(&block) ⇒ Object Also known as: on_slave, with_slave

Executes queries using the replica database. Fails over to primary if no replica is found. if you want to execute a block of code on the replica you can go:

Account.on_replica do
  Account.first
end

the first account will be found on the replica DB

For one-liners you can simply do

Account.on_replica.first



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# File 'lib/active_record_shards/connection_switcher.rb', line 103

def on_replica(&block)
  on_primary_or_replica(:replica, &block)
end

#on_replica? ⇒ Boolean Also known as: on_slave?

Returns:

  • (Boolean) 


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# File 'lib/active_record_shards/connection_switcher.rb', line 145

def on_replica?
  current_shard_selection.on_replica?
end

#on_replica_if(condition, &block) ⇒ Object Also known as: on_slave_if, with_slave_if 



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# File 'lib/active_record_shards/connection_switcher.rb', line 65

def on_replica_if(condition, &block)
  condition ? on_replica(&block) : yield
end

#on_replica_unless(condition, &block) ⇒ Object Also known as: on_slave_unless, with_slave_unless 



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# File 'lib/active_record_shards/connection_switcher.rb', line 70

def on_replica_unless(condition, &block)
  on_replica_if(!condition, &block)
end

#on_shard(shard) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 34

def on_shard(shard)
  old_options = current_shard_selection.options
  switch_connection(shard: shard) if supports_sharding?
  yield
ensure
  switch_connection(old_options)
end

#reset_primary_key_with_default_shard ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 166

def reset_primary_key_with_default_shard
  with_default_shard { reset_primary_key_without_default_shard }
end

#shard_names ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 158

def shard_names
  unless config_for_env.fetch(SHARD_NAMES_CONFIG_KEY, []).all? { |shard_name| shard_name.is_a?(Integer) }
    raise "All shard names must be integers: #{config_for_env[SHARD_NAMES_CONFIG_KEY].inspect}."
  end

  config_for_env[SHARD_NAMES_CONFIG_KEY] || []
end

#shards ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 47

def shards
  ShardSupport.new(self == ActiveRecord::Base ? nil : where(nil))
end

#supports_sharding? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_record_shards/connection_switcher.rb', line 141

def supports_sharding?
  shard_names.any?
end