aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/connection_handling.rb
blob: 3ce9aad5fc20a609e6399269a35cc9d96bc60736 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
# frozen_string_literal: true

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

    # Establishes the connection to the database. Accepts a hash as input where
    # the <tt>:adapter</tt> 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}[rdoc-ref:Core.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.
    def establish_connection(config_or_env = nil)
      config_hash = resolve_config_for_connection(config_or_env)
      connection_handler.establish_connection(config_hash)
    end

    # 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
    #
    # Returns an array of established connections.
    def connects_to(database: {})
      connections = []

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

        connections << handler.establish_connection(config_hash)
      end

      connections
    end

    # Connects to a database or role (ex writing, reading, or another
    # custom role) for the duration of the block.
    #
    # If a role is passed, Active Record will look up the connection
    # based on the requested role:
    #
    #   ActiveRecord::Base.connected_to(role: :writing) do
    #     Dog.create! # creates dog using dog connection
    #   end
    #
    #   ActiveRecord::Base.connected_to(role: :reading) do
    #     Dog.create! # throws exception because we're on a replica
    #   end
    #
    #   ActiveRecord::Base.connected_to(role: :unknown_ode) do
    #     # raises exception due to non-existent role
    #   end
    #
    # For cases where you may want to connect to a database outside of the model,
    # you can use +connected_to+ with a +database+ argument. The +database+ argument
    # expects a symbol that corresponds to the database key in your config.
    #
    # This will connect to a new database for the queries inside the block.
    #
    #   ActiveRecord::Base.connected_to(database: :animals_slow_replica) do
    #     Dog.run_a_long_query # runs a long query while connected to the +animals_slow_replica+
    #   end
    def connected_to(database: nil, role: nil, &blk)
      if database && role
        raise ArgumentError, "connected_to can only accept a `database` or a `role` argument, but not both arguments."
      elsif database
        if database.is_a?(Hash)
          role, database = database.first
          role = role.to_sym
        else
          role = database.to_sym
        end

        config_hash = resolve_config_for_connection(database)
        handler = lookup_connection_handler(role)

        with_handler(role) do
          handler.establish_connection(config_hash)
          yield
        end
      elsif role
        with_handler(role.to_sym, &blk)
      else
        raise ArgumentError, "must provide a `database` or a `role`."
      end
    end

    def lookup_connection_handler(handler_key) # :nodoc:
      connection_handlers[handler_key] ||= ActiveRecord::ConnectionAdapters::ConnectionHandler.new
    end

    def with_handler(handler_key, &blk) # :nodoc:
      handler = lookup_connection_handler(handler_key)
      swap_connection_handler(handler, &blk)
    end

    def resolve_config_for_connection(config_or_env) # :nodoc:
      raise "Anonymous class is not allowed." unless name

      config_or_env ||= DEFAULT_ENV.call.to_sym
      pool_name = self == Base ? "primary" : name
      self.connection_specification_name = pool_name

      resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(Base.configurations)
      config_hash = resolver.resolve(config_or_env, pool_name).symbolize_keys
      config_hash[:name] = pool_name

      config_hash
    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.
    def connection
      retrieve_connection
    end

    attr_writer :connection_specification_name

    # Return the specification name from the current class or its parent.
    def connection_specification_name
      if !defined?(@connection_specification_name) || @connection_specification_name.nil?
        return self == Base ? "primary" : superclass.connection_specification_name
      end
      @connection_specification_name
    end

    # 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.
    def connection_config
      connection_pool.spec.config
    end

    def connection_pool
      connection_handler.retrieve_connection_pool(connection_specification_name) || raise(ConnectionNotEstablished)
    end

    def retrieve_connection
      connection_handler.retrieve_connection(connection_specification_name)
    end

    # Returns +true+ if Active Record is connected.
    def connected?
      connection_handler.connected?(connection_specification_name)
    end

    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)
        self.connection_specification_name = nil
      end

      connection_handler.remove_connection(name)
    end

    def clear_cache! # :nodoc:
      connection.schema_cache.clear!
    end

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

    private

      def swap_connection_handler(handler, &blk) # :nodoc:
        old_handler, ActiveRecord::Base.connection_handler = ActiveRecord::Base.connection_handler, handler
        yield
      ensure
        ActiveRecord::Base.connection_handler = old_handler
      end
  end
end