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require 'thread'
begin
require 'pg'
rescue Gem::LoadError => e
raise Gem::LoadError, "You are trying to use the PostgreSQL ActionCable adapter, but do not have the proper gems installed. Add `gem 'pg'` to your Gemfile (and ensure its version is at the minimum required by ActionCable)."
end
module ActionCable
module SubscriptionAdapter
class PostgreSQL < Base # :nodoc:
# The storage instance used for broadcasting. Not intended for direct user use.
def broadcast(channel, payload)
with_connection do |pg_conn|
pg_conn.exec("NOTIFY #{pg_conn.escape_identifier(channel)}, '#{pg_conn.escape_string(payload)}'")
end
end
def subscribe(channel, callback, success_callback = nil)
listener.subscribe_to(channel, callback, success_callback)
end
def unsubscribe(channel, callback)
listener.unsubscribe_from(channel, callback)
end
def with_connection(&block) # :nodoc:
ActiveRecord::Base.connection_pool.with_connection do |ar_conn|
pg_conn = ar_conn.raw_connection
unless pg_conn.is_a?(PG::Connection)
raise 'ActiveRecord database must be Postgres in order to use the Postgres ActionCable storage adapter'
end
yield pg_conn
end
end
private
def listener
@listener ||= Listener.new(self)
end
class Listener
def initialize(adapter)
@adapter = adapter
@subscribers = Hash.new { |h,k| h[k] = [] }
@sync = Mutex.new
@queue = Queue.new
Thread.new do
Thread.current.abort_on_exception = true
listen
end
end
def listen
@adapter.with_connection do |pg_conn|
loop do
until @queue.empty?
action, channel, callback = @queue.pop(true)
escaped_channel = pg_conn.escape_identifier(channel)
if action == :listen
pg_conn.exec("LISTEN #{escaped_channel}")
::EM.next_tick(&callback) if callback
elsif action == :unlisten
pg_conn.exec("UNLISTEN #{escaped_channel}")
end
end
pg_conn.wait_for_notify(1) do |chan, pid, message|
@subscribers[chan].each do |callback|
::EM.next_tick { callback.call(message) }
end
end
end
end
end
def subscribe_to(channel, callback, success_callback)
@sync.synchronize do
if @subscribers[channel].empty?
@queue.push([:listen, channel, success_callback])
end
@subscribers[channel] << callback
end
end
def unsubscribe_from(channel, callback)
@sync.synchronize do
@subscribers[channel].delete(callback)
if @subscribers[channel].empty?
@queue.push([:unlisten, channel])
end
end
end
end
end
end
end
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