Module: ActiveRecordShards::ConnectionSwitcher

Defined in:
lib/active_record_shards/connection_switcher.rb,
lib/active_record_shards/connection_switcher-5-1.rb,
lib/active_record_shards/connection_switcher-6-0.rb,
lib/active_record_shards/connection_switcher-6-1.rb,
lib/active_record_shards/connection_switcher-7-0.rb

Defined Under Namespace

Classes: IsolationLevelError, LegacyConnectionHandlingError, PrimaryReplicaProxy

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 17

def self.extended(base)
  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!)

  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?)
end

Instance Method Details

#connection_specification_name ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher-5-1.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 142

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 137

def current_shard_selection
  cs = Thread.current.thread_variable_get(:shard_selection) || ShardSelection.new
  Thread.current.thread_variable_set(:shard_selection, cs)
end

#disallow_replica ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 125

def disallow_replica
  Thread.current[:__active_record_shards__disallow_replica_by_thread] ||= 0
end

#disallow_replica=(value) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 121

def disallow_replica=(value)
  Thread.current[:__active_record_shards__disallow_replica_by_thread] = value
end

#on_all_shards ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 46

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 101

def on_cx_switch_block(which, force: false, construct_ro_scope: nil, &block)
  self.disallow_replica += 1 if which == :primary

  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
  self.disallow_replica -= 1 if which == :primary
  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 37

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

#on_primary(&block) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 97

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 25

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

#on_primary_if(condition, &block) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 68

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

#on_primary_or_replica(which, &block) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 76

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 



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# File 'lib/active_record_shards/connection_switcher.rb', line 72

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

#on_replica(&block) ⇒ Object

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 93

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

#on_replica? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_record_shards/connection_switcher.rb', line 133

def on_replica?
  current_shard_selection.on_replica?
end

#on_replica_if(condition, &block) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 60

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

#on_replica_unless(condition, &block) ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 64

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 29

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

#shard_names ⇒ Object 



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# File 'lib/active_record_shards/connection_switcher.rb', line 146

def shard_names
  config_for_env[SHARD_NAMES_CONFIG_KEY] || []
end

#shards ⇒ Object 



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

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 129

def supports_sharding?
  shard_names.any?
end