ActiveRecord::ConnectionHandling (original) (raw)

Active Record Connection Handling

Methods

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P

R

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W

Constants

| DEFAULT_ENV | = | -> { RAILS_ENV.call || "default_env" } | | | ------------ | -- | ------------------------------------------------------------------------- | ------------------------------- | | | | | | | RAILS_ENV | = | -> { (Rails.env if defined?(Rails.env)) || ENV["RAILS_ENV"].presence | | ENV["RACK_ENV"].presence } | | | | | |

Attributes

[W] connection_specification_name

Instance Public methods

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

Source: show | on GitHub

def clear_query_caches_for_current_thread connection_handler.each_connection_pool do |pool| pool.clear_query_cache end end

Returns true if Active Record is connected.

Source: show | on GitHub

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

Connects to a role (e.g. 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 ActiveRecord::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 ActiveRecord::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

Source: show | on GitHub

def connected_to(role: nil, shard: nil, prevent_writes: false, &blk) if self != Base && !abstract_class raise NotImplementedError, "calling connected_to is only allowed on ActiveRecord::Base or abstract classes." end

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

unless role || shard raise ArgumentError, "must provide a shard and/or role." end

with_role_and_shard(role, shard, prevent_writes, &blk) end

Returns true if role is the current connected role and/or current connected shard. If no shard is passed, the default will be used.

ActiveRecord::Base.connected_to(role: :writing) do
  ActiveRecord::Base.connected_to?(role: :writing) #=> true
  ActiveRecord::Base.connected_to?(role: :reading) #=> false
end

ActiveRecord::Base.connected_to(role: :reading, shard: :shard_one) do
  ActiveRecord::Base.connected_to?(role: :reading, shard: :shard_one) #=> true
  ActiveRecord::Base.connected_to?(role: :reading, shard: :default) #=> false
  ActiveRecord::Base.connected_to?(role: :writing, shard: :shard_one) #=> true
end

Source: show | on GitHub

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

Passes the block to connected_to for every shard the model is configured to connect to (if any), and returns the results in an array.

Optionally, role and/or prevent_writes can be passed which will be forwarded to each connected_to call.

Source: show | on GitHub

def connected_to_all_shards(role: nil, prevent_writes: false, &blk) shard_keys.map do |shard| connected_to(shard: shard, role: role, prevent_writes: prevent_writes, &blk) end end

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

Source: show | on GitHub

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

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

prevent_writes = true if role == ActiveRecord.reading_role

append_to_connected_to_stack(role: role, shard: shard, prevent_writes: prevent_writes, klasses: classes) yield ensure connected_to_stack.pop end

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.

Source: show | on GitHub

def connecting_to(role: default_role, shard: default_shard, prevent_writes: false) prevent_writes = true if role == ActiveRecord.reading_role

append_to_connected_to_stack(role: role, shard: shard, prevent_writes: prevent_writes, klasses: [self]) end

Source: show | on GitHub 

def connection
  pool = connection_pool
  if pool.permanent_lease?
    case ActiveRecord.permanent_connection_checkout
    when :deprecated
      ActiveRecord.deprecator.warn <<~MESSAGE
        Called deprecated `ActiveRecord::Base.connection` method.

        Either use `with_connection` or `lease_connection`.
      MESSAGE
    when :disallowed
      raise ActiveRecordError, <<~MESSAGE
        Called deprecated `ActiveRecord::Base.connection` method.

        Either use `with_connection` or `lease_connection`.
      MESSAGE
    end
    pool.lease_connection
  else
    pool.active_connection
  end
end

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: "storage/development.sqlite3", adapter: "sqlite3"}>

Use only for reading.

Source: show | on GitHub

def connection_db_config connection_pool.db_config end

Source: show | on GitHub

def connection_pool connection_handler.retrieve_connection_pool(connection_specification_name, role: current_role, shard: current_shard, strict: true) end

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

Source: show | on GitHub

def connection_specification_name if @connection_specification_name.nil? return self == Base ? Base.name : superclass.connection_specification_name end @connection_specification_name end

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

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

This will look up the database config using the database_key and establish 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 supports read replicas as well. You can 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.

Source: show | on GitHub

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 = []

@shard_keys = shards.keys

if shards.empty? shards[:default] = database end

self.default_shard = shards.keys.first

shards.each do |shard, database_keys| database_keys.each do |role, database_key| db_config = resolve_config_for_connection(database_key)

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

end

connections end

establish_connection(config_or_env = nil)Link

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.

Source: show | on GitHub

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

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. The connection will remain leased for the entire duration of the request or job, or until release_connection is called.

Source: show | on GitHub

def lease_connection connection_pool.lease_connection end

prohibit_shard_swapping(enabled = true)Link

Prohibit swapping shards while inside of the passed block.

In some cases you may want to be able to swap shards but not allow a nested call to connected_to or connected_to_many to swap again. This is useful in cases you’re using sharding to provide per-request database isolation.

Source: show | on GitHub

def prohibit_shard_swapping(enabled = true) prev_value = ActiveSupport::IsolatedExecutionState[:active_record_prohibit_shard_swapping] ActiveSupport::IsolatedExecutionState[:active_record_prohibit_shard_swapping] = enabled yield ensure ActiveSupport::IsolatedExecutionState[:active_record_prohibit_shard_swapping] = prev_value end

Return the currently leased connection into the pool

Source: show | on GitHub

def release_connection connection_pool.release_connection end

Source: show | on GitHub

def remove_connection name = @connection_specification_name if defined?(@connection_specification_name)

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

Source: show | on GitHub

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

Source: show | on GitHub

def shard_keys connection_class_for_self.instance_variable_get(:@shard_keys) || [] end

Determine whether or not shard swapping is currently prohibited

Source: show | on GitHub

def shard_swapping_prohibited? ActiveSupport::IsolatedExecutionState[:active_record_prohibit_shard_swapping] end

while_preventing_writes(enabled = true, &block)Link

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.

Source: show | on GitHub

def while_preventing_writes(enabled = true, &block) connected_to(role: current_role, prevent_writes: enabled, &block) end

Checkouts a connection from the pool, yield it and then check it back in. If a connection was already leased via lease_connection or a parent call to with_connection, that same connection is yieled. If lease_connection is called inside the block, the connection won’t be checked back in. If connection is called inside the block, the connection won’t be checked back in unless the prevent_permanent_checkout argument is set to true.

Source: show | on GitHub

def with_connection(prevent_permanent_checkout: false, &block) connection_pool.with_connection(prevent_permanent_checkout: prevent_permanent_checkout, &block) end