require 'monitor'
require 'set'
module ActiveRecord
module ConnectionAdapters
class ConnectionPool
delegate :verification_timeout, :to => "::ActiveRecord::Base"
attr_reader :active_connections, :spec
def initialize(spec)
# The thread id -> adapter cache.
@active_connections = {}
# The ConnectionSpecification for this pool
@spec = spec
# The mutex used to synchronize pool access
@connection_mutex = Monitor.new
end
def active_connection_name #:nodoc:
Thread.current.object_id
end
def active_connection
active_connections[active_connection_name]
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
if conn = active_connections[active_connection_name]
conn
else
# retrieve_connection sets the cache key.
conn = retrieve_connection
active_connections[active_connection_name] = conn
end
end
# Clears the cache which maps classes to connections.
def clear_active_connections!
clear_entries!(@active_connections, [active_connection_name]) do |name, conn|
conn.disconnect!
end
end
# Clears the cache which maps classes
def clear_reloadable_connections!
@active_connections.each do |name, conn|
if conn.requires_reloading?
conn.disconnect!
@active_connections.delete(name)
end
end
end
# Verify active connections.
def verify_active_connections! #:nodoc:
remove_stale_cached_threads!(@active_connections) do |name, conn|
conn.disconnect!
end
active_connections.each_value do |connection|
connection.verify!(verification_timeout)
end
end
def retrieve_connection #:nodoc:
# Name is nil if establish_connection hasn't been called for
# some class along the inheritance chain up to AR::Base yet.
name = active_connection_name
if conn = active_connections[name]
# Verify the connection.
conn.verify!(verification_timeout)
else
self.set_connection spec
conn = active_connections[name]
end
conn or raise ConnectionNotEstablished
end
# Returns true if a connection that's accessible to this class has already been opened.
def connected?
active_connections[active_connection_name] ? true : false
end
# Disconnect all connections in the pool.
def disconnect!
clear_cache!(@active_connections) do |name, conn|
conn.disconnect!
end
end
# Set the connection for the class.
def set_connection(spec) #:nodoc:
if spec.kind_of?(ActiveRecord::ConnectionAdapters::AbstractAdapter)
active_connections[active_connection_name] = spec
elsif spec.kind_of?(ActiveRecord::Base::ConnectionSpecification)
config = spec.config.reverse_merge(:allow_concurrency => ActiveRecord::Base.allow_concurrency)
self.set_connection ActiveRecord::Base.send(spec.adapter_method, config)
else
raise ConnectionNotEstablished
end
end
synchronize :active_connection, :connection, :clear_active_connections!,
:clear_reloadable_connections!, :verify_active_connections!, :retrieve_connection,
:connected?, :disconnect!, :set_connection, :with => :@connection_mutex
private
def clear_cache!(cache, &block)
cache.each(&block) if block_given?
cache.clear
end
# Remove stale threads from the cache.
def remove_stale_cached_threads!(cache, &block)
stale = Set.new(cache.keys)
Thread.list.each do |thread|
stale.delete(thread.object_id) if thread.alive?
end
clear_entries!(cache, stale, &block)
end
def clear_entries!(cache, keys, &block)
keys.each do |key|
next unless cache.has_key?(key)
block.call(key, cache[key])
cache.delete(key)
end
end
end
module ConnectionHandlerMethods
def initialize(pools = {})
@connection_pools = pools
end
def connection_pools
@connection_pools ||= {}
end
def establish_connection(name, spec)
@connection_pools[name] = ConnectionAdapters::ConnectionPool.new(spec)
end
# for internal use only and for testing
def active_connections #:nodoc:
@connection_pools.inject({}) do |hash,kv|
hash[kv.first] = kv.last.active_connection
hash.delete(kv.first) unless hash[kv.first]
hash
end
end
# Clears the cache which maps classes to connections.
def clear_active_connections!
@connection_pools.each_value {|pool| pool.clear_active_connections! }
end
# Clears the cache which maps classes
def clear_reloadable_connections!
@connection_pools.each_value {|pool| pool.clear_reloadable_connections! }
end
def clear_all_connections!
@connection_pools.each_value {|pool| pool.disconnect! }
end
# Verify active connections.
def verify_active_connections! #:nodoc:
@connection_pools.each_value {|pool| pool.verify_active_connections!}
end
# Locate the connection of the nearest super class. This can be an
# active or defined connection: if it is the latter, it will be
# opened and set as the active connection for the class it was defined
# for (not necessarily the current class).
def retrieve_connection(klass) #:nodoc:
pool = retrieve_connection_pool(klass)
(pool && pool.connection) or raise ConnectionNotEstablished
end
# Returns true if a connection that's accessible to this class has already been opened.
def connected?(klass)
retrieve_connection_pool(klass).connected?
end
# Remove the connection for this class. This will close the active
# connection and the defined connection (if they exist). The result
# can be used as an argument for establish_connection, for easily
# re-establishing the connection.
def remove_connection(klass)
pool = @connection_pools[klass.name]
@connection_pools.delete_if { |key, value| value == pool }
pool.disconnect! if pool
pool.spec.config if pool
end
private
def retrieve_connection_pool(klass)
loop do
pool = @connection_pools[klass.name]
return pool if pool
return nil if ActiveRecord::Base == klass
klass = klass.superclass
end
end
end
# This connection handler is not thread-safe, as it does not protect access
# to the underlying connection pools.
class SingleThreadConnectionHandler
include ConnectionHandlerMethods
end
# This connection handler is thread-safe. Each access or modification of a thread
# pool is synchronized by an internal monitor.
class MultipleThreadConnectionHandler
attr_reader :connection_pools_lock
include ConnectionHandlerMethods
def initialize(pools = {})
super
@connection_pools_lock = Monitor.new
end
# Apply monitor to all public methods that access the pool.
synchronize :establish_connection, :retrieve_connection,
:connected?, :remove_connection, :active_connections,
:clear_active_connections!, :clear_reloadable_connections!,
:clear_all_connections!, :verify_active_connections!,
:with => :connection_pools_lock
end
end
end
