Class: Synapse::ServiceWatcher::ZookeeperDnsWatcher::Dns

Inherits:
DnsWatcher show all
Defined in:
lib/synapse/service_watcher/zookeeper_dns.rb

Constant Summary

Constants inherited from BaseWatcher

BaseWatcher::LEADER_WARN_INTERVAL

Instance Attribute Summary collapse

Attributes inherited from BaseWatcher

#name, #revision

Instance Method Summary collapse

Methods inherited from DnsWatcher

#ping?, #start

Methods inherited from BaseWatcher

#backends, #config_for_generator, #haproxy, #ping?, #start

Methods included from Logging

configure_logger_for, #log, logger_for

Constructor Details

#initialize(opts = {}, parent = nil, synapse, message_queue) ⇒ Dns

Returns a new instance of Dns.



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# File 'lib/synapse/service_watcher/zookeeper_dns.rb', line 54

def initialize(opts={}, parent=nil, synapse, message_queue)
  @message_queue = message_queue
  @parent = parent

  super(opts, synapse)
end

Instance Attribute Details

#discovery_servers ⇒ Object

Overrides the discovery_servers method on the parent class



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# File 'lib/synapse/service_watcher/zookeeper_dns.rb', line 52

def discovery_servers
  @discovery_servers
end

Instance Method Details

#stop ⇒ Object 



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# File 'lib/synapse/service_watcher/zookeeper_dns.rb', line 61

def stop
  @message_queue.push(Messages::STOP_WATCHER_MESSAGE)
end

#watch ⇒ Object 



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# File 'lib/synapse/service_watcher/zookeeper_dns.rb', line 65

def watch
  last_resolution = nil
  while true
    # Blocks on message queue, the message will be a signal to stop
    # watching, to check a new set of servers from ZK, or to re-resolve
    # the DNS (triggered every check_interval seconds)
    message = @message_queue.pop

    log.debug "synapse: received message #{message.inspect}"

    case message
    when Messages::StopWatcher
      break
    when Messages::NewServers
      self.discovery_servers = message.servers
    when Messages::CheckInterval
      # Proceed to re-resolve the DNS
    else
      raise Messages::InvalidMessageError,
        "Received unrecognized message: #{message.inspect}"
    end

    # Empty servers means we haven't heard back from ZK yet or ZK is
    # empty.  This should only occur if we don't get results from ZK
    # within check_interval seconds or if ZK is empty.
    if self.discovery_servers.nil? || self.discovery_servers.empty?
      log.warn "synapse: no backends for service #{@name}"
    else
      # Resolve DNS names with the nameserver
      current_resolution = resolve_servers
      unless last_resolution == current_resolution
        last_resolution = current_resolution
        configure_backends(last_resolution)

        # Propagate revision updates down to ZookeeperDnsWatcher, so
        # that stanza cache can work properly.
        @revision += 1
        @parent.reconfigure! unless @parent.nil?
      end
    end
  end
end