Class: Synapse::ServiceWatcher::BaseWatcher

Inherits:
Object
  • Object
show all
Includes:
Logging
Defined in:
lib/synapse/service_watcher/base.rb

Constant Summary collapse

LEADER_WARN_INTERVAL = 
30

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Logging

configure_logger_for, #log, logger_for

Constructor Details

#initialize(opts = {}, synapse) ⇒ BaseWatcher

Returns a new instance of BaseWatcher.



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# File 'lib/synapse/service_watcher/base.rb', line 12

def initialize(opts={}, synapse)
  super()

  @synapse = synapse

  # set required service parameters
  %w{name discovery haproxy}.each do |req|
    raise ArgumentError, "missing required option #{req}" unless opts[req]
  end

  @name = opts['name']
  @discovery = opts['discovery']

  # deprecated singular filter
  @singular_label_filter = @discovery['label_filter']
  unless @singular_label_filter.nil?
    log.warn "synapse: `label_filter` parameter is deprecated; use `label_filters` -- an array"
  end

  @label_filters = [@singular_label_filter, @discovery['label_filters']].flatten.compact

  @leader_election = opts['leader_election'] || false
  @leader_last_warn = Time.now - LEADER_WARN_INTERVAL

  # the haproxy config
  @haproxy = opts['haproxy']
  @haproxy['server_options'] ||= ""
  @haproxy['server_port_override'] ||= nil
  %w{backend frontend listen}.each do |sec|
    @haproxy[sec] ||= []
  end

  unless @haproxy.include?('port')
    log.warn "synapse: service #{name}: haproxy config does not include a port; only backend sections for the service will be created; you must move traffic there manually using configuration in `extra_sections`"
  end

  # set initial backends to default servers, if any
  @default_servers = opts['default_servers'] || []
  @backends = @default_servers

  @keep_default_servers = opts['keep_default_servers'] || false

  # If there are no default servers and a watcher reports no backends, then
  # use the previous backends that we already know about.
  @use_previous_backends = opts.fetch('use_previous_backends', true)

  # set a flag used to tell the watchers to exit
  # this is not used in every watcher
  @should_exit = false

  validate_discovery_opts
end

Instance Attribute Details

#haproxy ⇒ Object (readonly)

Returns the value of attribute haproxy.



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# File 'lib/synapse/service_watcher/base.rb', line 10

def haproxy
  @haproxy
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/synapse/service_watcher/base.rb', line 10

def name
  @name
end

Instance Method Details

#backends ⇒ Object 



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# File 'lib/synapse/service_watcher/base.rb', line 82

def backends
  filtered = backends_filtered_by_labels

  if @leader_election
    failure_warning = nil
    if filtered.empty?
      failure_warning = "synapse: service #{@name}: leader election failed: no backends to choose from"
    end

    all_backends_have_ids = filtered.all?{|b| b.key?('id') && b['id']}
    unless all_backends_have_ids
      failure_warning = "synapse: service #{@name}: leader election failed; not all backends include an id"
    end

    # no problems encountered, lets do the leader election
    if failure_warning.nil?
      smallest = filtered.sort_by{ |b| b['id']}.first
      log.debug "synapse: leader election chose one of #{filtered.count} backends " \
        "(#{smallest['host']}:#{smallest['port']} with id #{smallest['id']})"

      return [smallest]

    # we had some sort of problem, lets log about it
    elsif (Time.now - @leader_last_warn) > LEADER_WARN_INTERVAL
      @leader_last_warn = Time.now
      log.warn failure_warning
      return []
    end
  end

  return filtered
end

#ping? ⇒ Boolean

this should be overridden to do a health check of the watcher

Returns:

  • (Boolean) 


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# File 'lib/synapse/service_watcher/base.rb', line 78

def ping?
  true
end

#start ⇒ Object

this should be overridden to actually start your watcher



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# File 'lib/synapse/service_watcher/base.rb', line 66

def start
  log.info "synapse: starting stub watcher; this means doing nothing at all!"
end

#stop ⇒ Object

this should be overridden to actually stop your watcher if necessary if you are running a thread, your loop should run ‘until @should_exit`



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# File 'lib/synapse/service_watcher/base.rb', line 72

def stop
  log.info "synapse: stopping watcher #{self.name} using default stop handler"
  @should_exit = true
end