Class: MessageBus::Postgres::ReliablePubSub

Inherits:
Object
  • Object
show all
Defined in:
lib/message_bus/backends/postgres.rb

Constant Summary collapse

UNSUB_MESSAGE = 
"$$UNSUBSCRIBE"

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config = {}, max_backlog_size = 1000) ⇒ ReliablePubSub

max_backlog_size is per multiplexed channel



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# File 'lib/message_bus/backends/postgres.rb', line 224

def initialize(config = {}, max_backlog_size = 1000)
  @config = config
  @max_backlog_size = max_backlog_size
  @max_global_backlog_size = 2000
  # after 7 days inactive backlogs will be removed
  @max_backlog_age = 604800
  @clear_every = config[:clear_every] || 1
end

Instance Attribute Details

#clear_every ⇒ Object

Returns the value of attribute clear_every.



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# File 'lib/message_bus/backends/postgres.rb', line 215

def clear_every
  @clear_every
end

#max_backlog_age ⇒ Object

Returns the value of attribute max_backlog_age.



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# File 'lib/message_bus/backends/postgres.rb', line 215

def max_backlog_age
  @max_backlog_age
end

#max_backlog_size ⇒ Object

Returns the value of attribute max_backlog_size.



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# File 'lib/message_bus/backends/postgres.rb', line 215

def max_backlog_size
  @max_backlog_size
end

#max_global_backlog_size ⇒ Object

Returns the value of attribute max_global_backlog_size.



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# File 'lib/message_bus/backends/postgres.rb', line 215

def max_global_backlog_size
  @max_global_backlog_size
end

#subscribed ⇒ Object (readonly)

Returns the value of attribute subscribed.



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# File 'lib/message_bus/backends/postgres.rb', line 214

def subscribed
  @subscribed
end

Class Method Details

.reset!(config) ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 219

def self.reset!(config)
  MessageBus::Postgres::Client.new(config).reset!
end

Instance Method Details

#after_fork ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 241

def after_fork
  client.reconnect
end

#backend ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 237

def backend
  :postgres
end

#backlog(channel, last_id = nil) ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 281

def backlog(channel, last_id = nil)
  items = client.backlog channel, last_id.to_i

  items.map! do |id, data|
    MessageBus::Message.new id, id, channel, data
  end
end

#client ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 250

def client
  @client ||= new_connection
end

#get_message(channel, message_id) ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 297

def get_message(channel, message_id)
  if data = client.get_value(channel, message_id)
    MessageBus::Message.new message_id, message_id, channel, data
  else
    nil
  end
end

#global_backlog(last_id = nil) ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 289

def global_backlog(last_id = nil)
  items = client.global_backlog last_id.to_i

  items.map! do |id, channel, data|
    MessageBus::Message.new id, id, channel, data
  end
end

#global_subscribe(last_id = nil, &blk) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/message_bus/backends/postgres.rb', line 333

def global_subscribe(last_id = nil, &blk)
  raise ArgumentError unless block_given?
  highest_id = last_id

  begin
    client.subscribe(postgresql_channel_name) do |on|
      h = {}

      on.subscribe do
        if highest_id
          process_global_backlog(highest_id) do |m|
            h[m.global_id] = true
            yield m
          end
        end
        h = nil if h.empty?
        @subscribed = true
      end

      on.unsubscribe do
        @subscribed = false
      end

      on.message do |c, m|
        if m == UNSUB_MESSAGE
          @subscribed = false
          return
        end
        m = MessageBus::Message.decode m

        # we have 3 options
        #
        # 1. message came in the correct order GREAT, just deal with it
        # 2. message came in the incorrect order COMPLICATED, wait a tiny bit and clear backlog
        # 3. message came in the incorrect order and is lowest than current highest id, reset

        if h
          # If already yielded during the clear backlog when subscribing,
          # don't yield a duplicate copy.
          unless h.delete(m.global_id)
            h = nil if h.empty?
            yield m
          end
        else
          yield m
        end
      end
    end
  rescue => error
    @config[:logger].warn "#{error} subscribe failed, reconnecting in 1 second. Call stack\n#{error.backtrace.join("\n")}"
    sleep 1
    retry
  end
end

#global_unsubscribe ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 328

def global_unsubscribe
  client.publish(postgresql_channel_name, UNSUB_MESSAGE)
  @subscribed = false
end

#last_id(channel) ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 277

def last_id(channel)
  client.max_id(channel)
end

#new_connection ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 233

def new_connection
  MessageBus::Postgres::Client.new(@config)
end

#postgresql_channel_name ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 245

def postgresql_channel_name
  db = @config[:db] || 0
  "_message_bus_#{db}"
end

#process_global_backlog(highest_id) ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 315

def process_global_backlog(highest_id)
  if highest_id > client.max_id
    highest_id = 0
  end

  global_backlog(highest_id).each do |old|
    yield old
    highest_id = old.global_id
  end

  highest_id
end

#publish(channel, data, opts = nil) ⇒ Object 



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# File 'lib/message_bus/backends/postgres.rb', line 259

def publish(channel, data, opts = nil)

  # TODO in memory queue?

  client = self.client
  backlog_id = client.add(channel, data)
  msg = MessageBus::Message.new backlog_id, backlog_id, channel, data
  payload = msg.encode
  client.publish postgresql_channel_name, payload
  if backlog_id % clear_every == 0
    client.clear_global_backlog(backlog_id, @max_global_backlog_size)
    client.expire(@max_backlog_age)
    client.clear_channel_backlog(channel, backlog_id, @max_backlog_size)
  end

  backlog_id
end

#reset! ⇒ Object

use with extreme care, will nuke all of the data



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# File 'lib/message_bus/backends/postgres.rb', line 255

def reset!
  client.reset!
end

#subscribe(channel, last_id = nil) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/message_bus/backends/postgres.rb', line 305

def subscribe(channel, last_id = nil)
  # trivial implementation for now,
  #   can cut down on connections if we only have one global subscriber
  raise ArgumentError unless block_given?

  global_subscribe(last_id) do |m|
    yield m if m.channel == channel
  end
end