/usr/lib/ruby/vendor_ruby/sequel/connection_pool/sharded_threaded.rb is in ruby-sequel 4.15.0-1.
This file is owned by root:root, with mode 0o644.
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# The slowest and most advanced connection, dealing with both multi-threaded
# access and configurations with multiple shards/servers.
#
# In addition, this pool subclass also handles scheduling in-use connections
# to be removed from the pool when they are returned to it.
class Sequel::ShardedThreadedConnectionPool < Sequel::ThreadedConnectionPool
# The following additional options are respected:
# :servers :: A hash of servers to use. Keys should be symbols. If not
# present, will use a single :default server.
# :servers_hash :: The base hash to use for the servers. By default,
# Sequel uses Hash.new(:default). You can use a hash with a default proc
# that raises an error if you want to catch all cases where a nonexistent
# server is used.
def initialize(db, opts = OPTS)
super
@available_connections = {}
@connections_to_remove = []
@servers = opts.fetch(:servers_hash, Hash.new(:default))
add_servers([:default])
add_servers(opts[:servers].keys) if opts[:servers]
end
# Adds new servers to the connection pool. Primarily used in conjunction with master/slave
# or shard configurations. Allows for dynamic expansion of the potential slaves/shards
# at runtime. servers argument should be an array of symbols.
def add_servers(servers)
sync do
servers.each do |server|
unless @servers.has_key?(server)
@servers[server] = server
@available_connections[server] = []
@allocated[server] = {}
end
end
end
end
# A hash of connections currently being used for the given server, key is the
# Thread, value is the connection. Nonexistent servers will return nil. Treat
# this as read only, do not modify the resulting object.
def allocated(server=:default)
@allocated[server]
end
# Yield all of the available connections, and the ones currently allocated to
# this thread. This will not yield connections currently allocated to other
# threads, as it is not safe to operate on them. This holds the mutex while
# it is yielding all of the connections, which means that until
# the method's block returns, the pool is locked.
def all_connections
t = Thread.current
sync do
@allocated.values.each do |threads|
threads.each do |thread, conn|
yield conn if t == thread
end
end
@available_connections.values.each{|v| v.each{|c| yield c}}
end
end
# An array of connections opened but not currently used, for the given
# server. Nonexistent servers will return nil. Treat this as read only, do
# not modify the resulting object.
def available_connections(server=:default)
@available_connections[server]
end
# The total number of connections opened for the given server, should
# be equal to available_connections.length + allocated.length. Nonexistent
# servers will return the created count of the default server.
def size(server=:default)
server = @servers[server]
@allocated[server].length + @available_connections[server].length
end
# Removes all connections currently available on all servers, optionally
# yielding each connection to the given block. This method has the effect of
# disconnecting from the database, assuming that no connections are currently
# being used. If connections are being used, they are scheduled to be
# disconnected as soon as they are returned to the pool.
#
# Once a connection is requested using #hold, the connection pool
# creates new connections to the database. Options:
# :server :: Should be a symbol specifing the server to disconnect from,
# or an array of symbols to specify multiple servers.
def disconnect(opts=OPTS)
sync do
(opts[:server] ? Array(opts[:server]) : @servers.keys).each do |s|
disconnect_server(s)
end
end
end
# Chooses the first available connection to the given server, or if none are
# available, creates a new connection. Passes the connection to the supplied
# block:
#
# pool.hold {|conn| conn.execute('DROP TABLE posts')}
#
# Pool#hold is re-entrant, meaning it can be called recursively in
# the same thread without blocking.
#
# If no connection is immediately available and the pool is already using the maximum
# number of connections, Pool#hold will block until a connection
# is available or the timeout expires. If the timeout expires before a
# connection can be acquired, a Sequel::PoolTimeout is
# raised.
def hold(server=:default)
server = pick_server(server)
t = Thread.current
if conn = owned_connection(t, server)
return yield(conn)
end
begin
unless conn = acquire(t, server)
time = Time.now
timeout = time + @timeout
sleep_time = @sleep_time
sleep sleep_time
until conn = acquire(t, server)
raise(::Sequel::PoolTimeout) if Time.now > timeout
sleep sleep_time
end
end
yield conn
rescue Sequel::DatabaseDisconnectError
sync{@connections_to_remove << conn} if conn
raise
ensure
sync{release(t, conn, server)} if conn
end
end
# Remove servers from the connection pool. Primarily used in conjunction with master/slave
# or shard configurations. Similar to disconnecting from all given servers,
# except that after it is used, future requests for the server will use the
# :default server instead.
def remove_servers(servers)
sync do
raise(Sequel::Error, "cannot remove default server") if servers.include?(:default)
servers.each do |server|
if @servers.include?(server)
disconnect_server(server)
@available_connections.delete(server)
@allocated.delete(server)
@servers.delete(server)
end
end
end
end
# Return an array of symbols for servers in the connection pool.
def servers
sync{@servers.keys}
end
def pool_type
:sharded_threaded
end
private
# Assigns a connection to the supplied thread for the given server, if one
# is available. The calling code should NOT already have the mutex when
# calling this.
def acquire(thread, server)
sync do
if conn = available(server)
allocated(server)[thread] = conn
end
end
end
# Returns an available connection to the given server. If no connection is
# available, tries to create a new connection. The calling code should already
# have the mutex before calling this.
def available(server)
next_available(server) || make_new(server)
end
# Return a connection to the pool of available connections for the server,
# returns the connection. The calling code should already have the mutex
# before calling this.
def checkin_connection(server, conn)
available_connections(server) << conn
conn
end
# Disconnect from the given server. Disconnects available connections
# immediately, and schedules currently allocated connections for disconnection
# as soon as they are returned to the pool. The calling code should already
# have the mutex before calling this.
def disconnect_server(server)
if conns = available_connections(server)
conns.each{|conn| db.disconnect_connection(conn)}
conns.clear
end
@connections_to_remove.concat(allocated(server).values)
end
# Creates a new connection to the given server if the size of the pool for
# the server is less than the maximum size of the pool. The calling code
# should already have the mutex before calling this.
def make_new(server)
if (n = size(server)) >= @max_size
allocated(server).to_a.each{|t, c| release(t, c, server) unless t.alive?}
n = nil
end
default_make_new(server) if (n || size(server)) < @max_size
end
# Return the next available connection in the pool for the given server, or nil
# if there is not currently an available connection for the server.
# The calling code should already have the mutex before calling this.
def next_available(server)
case @connection_handling
when :stack
available_connections(server).pop
else
available_connections(server).shift
end
end
# Returns the connection owned by the supplied thread for the given server,
# if any. The calling code should NOT already have the mutex before calling this.
def owned_connection(thread, server)
sync{@allocated[server][thread]}
end
# If the server given is in the hash, return it, otherwise, return the default server.
def pick_server(server)
sync{@servers[server]}
end
# Releases the connection assigned to the supplied thread and server. If the
# server or connection given is scheduled for disconnection, remove the
# connection instead of releasing it back to the pool.
# The calling code should already have the mutex before calling this.
def release(thread, conn, server)
if @connections_to_remove.include?(conn)
remove(thread, conn, server)
else
conn = allocated(server).delete(thread)
if @connection_handling == :disconnect
db.disconnect_connection(conn)
else
checkin_connection(server, conn)
end
end
end
# Removes the currently allocated connection from the connection pool. The
# calling code should already have the mutex before calling this.
def remove(thread, conn, server)
@connections_to_remove.delete(conn)
allocated(server).delete(thread) if @servers.include?(server)
db.disconnect_connection(conn)
end
CONNECTION_POOL_MAP[[false, true]] = self
end
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