Class: Zookeeper::Continuation

Inherits:
Object
  • Object
show all
Includes:
Constants, Logger
Defined in:
lib/zookeeper/continuation.rb

Overview

sigh, slightly different than the userland callbacks, the continuation provides sync call semantics around an async api

Defined Under Namespace

Classes: Registry

Constant Summary collapse

OPERATION_TIMEOUT =

seconds

30
CALLBACK_ARG_IDX =

sigh what is the index in the *args array of the 'callback' param

{
  :get => 2,
  :set => 3,
  :exists => 2,
  :create => 3,
  :delete => 3,
  :get_acl => 2,
  :set_acl => 3,
  :get_children => 2,
  :state => 0,
}
METH_TO_ASYNC_RESULT_KEYS =

maps the method name to the async return hash keys it should use to deliver the results

{
  :get          => [:rc, :data, :stat],
  :set          => [:rc, :stat],
  :exists       => [:rc, :stat],
  :create       => [:rc, :string],
  :delete       => [:rc],
  :get_acl      => [:rc, :acl, :stat],
  :set_acl      => [:rc],
  :get_children => [:rc, :strings, :stat],
}

Constants included from Constants

Zookeeper::Constants::CONNECTED_EVENT_VALUES, Zookeeper::Constants::EVENT_TYPE_NAMES, Zookeeper::Constants::STATE_NAMES, Zookeeper::Constants::ZAPIERROR, Zookeeper::Constants::ZAUTHFAILED, Zookeeper::Constants::ZBADARGUMENTS, Zookeeper::Constants::ZBADVERSION, Zookeeper::Constants::ZCLOSING, Zookeeper::Constants::ZCONNECTIONLOSS, Zookeeper::Constants::ZDATAINCONSISTENCY, Zookeeper::Constants::ZINVALIDACL, Zookeeper::Constants::ZINVALIDCALLBACK, Zookeeper::Constants::ZINVALIDSTATE, Zookeeper::Constants::ZKRB_ASYNC_CONTN_ID, Zookeeper::Constants::ZKRB_GLOBAL_CB_REQ, Zookeeper::Constants::ZMARSHALLINGERROR, Zookeeper::Constants::ZNOAUTH, Zookeeper::Constants::ZNOCHILDRENFOREPHEMERALS, Zookeeper::Constants::ZNODEEXISTS, Zookeeper::Constants::ZNONODE, Zookeeper::Constants::ZNOTEMPTY, Zookeeper::Constants::ZNOTHING, Zookeeper::Constants::ZOK, Zookeeper::Constants::ZOO_ASSOCIATING_STATE, Zookeeper::Constants::ZOO_AUTH_FAILED_STATE, Zookeeper::Constants::ZOO_CHANGED_EVENT, Zookeeper::Constants::ZOO_CHILD_EVENT, Zookeeper::Constants::ZOO_CLOSED_STATE, Zookeeper::Constants::ZOO_CONNECTED_STATE, Zookeeper::Constants::ZOO_CONNECTING_STATE, Zookeeper::Constants::ZOO_CREATED_EVENT, Zookeeper::Constants::ZOO_DELETED_EVENT, Zookeeper::Constants::ZOO_EPHEMERAL, Zookeeper::Constants::ZOO_EXPIRED_SESSION_STATE, Zookeeper::Constants::ZOO_LOG_LEVEL_DEBUG, Zookeeper::Constants::ZOO_LOG_LEVEL_ERROR, Zookeeper::Constants::ZOO_LOG_LEVEL_INFO, Zookeeper::Constants::ZOO_LOG_LEVEL_WARN, Zookeeper::Constants::ZOO_NOTWATCHING_EVENT, Zookeeper::Constants::ZOO_SEQUENCE, Zookeeper::Constants::ZOO_SESSION_EVENT, Zookeeper::Constants::ZOPERATIONTIMEOUT, Zookeeper::Constants::ZRUNTIMEINCONSISTENCY, Zookeeper::Constants::ZSESSIONEXPIRED, Zookeeper::Constants::ZSESSIONMOVED, Zookeeper::Constants::ZSYSTEMERROR, Zookeeper::Constants::ZUNIMPLEMENTED

Constants included from ACLs::Constants

ACLs::Constants::ZOO_ANYONE_ID_UNSAFE, ACLs::Constants::ZOO_AUTH_IDS, ACLs::Constants::ZOO_CREATOR_ALL_ACL, ACLs::Constants::ZOO_OPEN_ACL_UNSAFE, ACLs::Constants::ZOO_PERM_ADMIN, ACLs::Constants::ZOO_PERM_ALL, ACLs::Constants::ZOO_PERM_CREATE, ACLs::Constants::ZOO_PERM_DELETE, ACLs::Constants::ZOO_PERM_READ, ACLs::Constants::ZOO_PERM_WRITE, ACLs::Constants::ZOO_READ_ACL_UNSAFE

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Logger

included, set_default

Methods included from Constants

#event_by_value, #state_by_value

Constructor Details

#initialize(meth, *args) ⇒ Continuation


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# File 'lib/zookeeper/continuation.rb', line 83

def initialize(meth, *args)
  @meth   = meth
  @args   = args.freeze
  @mutex  = Monitor.new
  @cond   = @mutex.new_cond
  @rval   = nil

  # make this error reporting more robust if necessary, right now, just set to state
  @error  = nil
end

Instance Attribute Details

#argsObject (readonly)

Returns the value of attribute args


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# File 'lib/zookeeper/continuation.rb', line 81

def args
  @args
end

#blockObject

Returns the value of attribute block


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# File 'lib/zookeeper/continuation.rb', line 79

def block
  @block
end

#methObject

Returns the value of attribute meth


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# File 'lib/zookeeper/continuation.rb', line 79

def meth
  @meth
end

#rvalObject

Returns the value of attribute rval


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# File 'lib/zookeeper/continuation.rb', line 79

def rval
  @rval
end

Instance Method Details

#call(hash) ⇒ Object

receive the response from the server, set @rval, notify caller


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# File 'lib/zookeeper/continuation.rb', line 139

def call(hash)
  logger.debug { "continuation req_id #{req_id}, got hash: #{hash.inspect}" }
  @rval = hash.values_at(*METH_TO_ASYNC_RESULT_KEYS.fetch(meth))
  logger.debug { "delivering result #{@rval.inspect}" }
  deliver!
end

#req_idObject


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# File 'lib/zookeeper/continuation.rb', line 178

def req_id
  @args.first
end

#shutdown!Object

interrupt the sleeping thread with a NotConnected error


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# File 'lib/zookeeper/continuation.rb', line 187

def shutdown!
  @mutex.synchronize do
    return if @rval or @error
    @error = :shutdown
    @cond.broadcast
  end
end

#state_call?Boolean


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# File 'lib/zookeeper/continuation.rb', line 182

def state_call?
  @meth == :state
end

#submit(czk) ⇒ Object

this method is called by the event thread to submit the request passed the CZookeeper instance, makes the async call and deals with the results

BTW: in case you were wondering this is a completely stupid implementation, but it's more important to get something working and passing specs, then refactor to make everything sane


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# File 'lib/zookeeper/continuation.rb', line 158

def submit(czk)
  state = czk.zkrb_state    # check the state of the connection

  if @meth == :state        # if the method is a state call
    @rval = [state]         # we're done, no error
    return deliver!

  elsif state != ZOO_CONNECTED_STATE  # otherwise, we must be connected
    @error = state                    # so set the error
    return deliver!                   # and we're out
  end

  rc, *_ = czk.__send__(:"zkrb_#{@meth}", *async_args)
  
  if user_callback? or (rc != ZOK)  # async call, or we failed to submit it
    @rval = [rc]                    # create the repsonse
    deliver!                        # wake the caller and we're out
  end
end

#user_callback?Boolean


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# File 'lib/zookeeper/continuation.rb', line 146

def user_callback?
  !!@args.at(callback_arg_idx)
end

#valueObject

the caller calls this method and receives the response from the async loop this method has a hard-coded 30 second timeout as a safety feature. No call should take more than 20s (as the session timeout is set to 20s) so if any call takes longer than that, something has gone horribly wrong.

Raises:

  • (ContinuationTimeoutError)

    if a response is not received within 30s


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# File 'lib/zookeeper/continuation.rb', line 101

def value
  time_to_stop = Time.now + OPERATION_TIMEOUT
  now = nil

  @mutex.synchronize do
    while true
      now = Time.now
      break if @rval or @error or (now > time_to_stop)

      deadline = time_to_stop.to_f - now.to_f
      @cond.wait(deadline)
    end

    if (now > time_to_stop) and !@rval and !@error
      raise Exceptions::ContinuationTimeoutError, "response for meth: #{meth.inspect}, args: #{@args.inspect}, not received within #{OPERATION_TIMEOUT} seconds"
    end

    case @error
    when nil
      # ok, nothing to see here, carry on
    when :shutdown
      raise Exceptions::NotConnected, "the connection is shutting down"
    when ZOO_EXPIRED_SESSION_STATE
      raise Exceptions::SessionExpired, "connection has expired"
    else
      raise Exceptions::NotConnected, "connection state is #{STATE_NAMES[@error]}"
    end

    case @rval.length
    when 1
      return @rval.first
    else
      return @rval
    end
  end
end