method

try_to_checkout_new_connection

v8.1.1 - Show latest stable - Class: ActiveRecord::ConnectionAdapters::ConnectionPool

try_to_checkout_new_connection()

private

If the pool is not at a @max_connections limit, establish new connection. Connecting to the DB is done outside main synchronized section.

If a block is supplied, it is an additional constraint (checked while holding the pool lock) on whether a new connection should be established.

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 1221
        def try_to_checkout_new_connection
          # first in synchronized section check if establishing new conns is allowed
          # and increment @now_connecting, to prevent overstepping this pool's @max_connections
          # constraint
          do_checkout = synchronize do
            return if self.discarded?

            if @threads_blocking_new_connections.zero? && (@max_connections.nil? || (@connections.size + @now_connecting) < @max_connections) && (!block_given? || yield)
              if @connections.size > 0 || @original_context != ActiveSupport::IsolatedExecutionState.context
                @activated = true
              end

              @now_connecting += 1
            end
          end
          if do_checkout
            begin
              # if successfully incremented @now_connecting establish new connection
              # outside of synchronized section
              conn = checkout_new_connection
            ensure
              synchronize do
                @now_connecting -= 1
                if conn
                  if self.discarded?
                    conn.discard!
                  else
                    adopt_connection(conn)
                    # returned conn needs to be already leased
                    conn.lease
                  end
                end
              end
            end
          end
        end

try_to_checkout_new_connection

Related methods