Class: Amazon::WebServices::MTurk::MechanicalTurkErrorHandler

Inherits:
Object
  • Object
show all
Includes:
Util::Logging
Defined in:
lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb

Constant Summary collapse

REQUIRED_PARAMETERS = 
[:Relay]
RETRY_PRE =

Commands with these prefixes can be retried if we are unsure of success

%w( search get register update disable assign set dispose )
MAX_RETRY =

Max number of times to retry a call

6
BACKOFF_BASE =

Base used in Exponential Backoff retry delay

2
BACKOFF_INITIAL =

Scale factor for Exponential Backoff retry delay

0.1
RESULT_PATTERN =

Matching pattern to find a ‘Results’ element in the Response

/Result/
ACCEPTABLE_RESULTS =

Additional elements to be considered a ‘Result’ despite not matching RESULT_PATTERN

%w( HIT Qualification QualificationType QualificationRequest Information )

Instance Method Summary collapse

Methods included from Util::Logging

#log, #set_log

Constructor Details

#initialize(args) ⇒ MechanicalTurkErrorHandler

Returns a new instance of MechanicalTurkErrorHandler.



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# File 'lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb', line 33

def initialize( args )
  missing_parameters = REQUIRED_PARAMETERS - args.keys
  raise "Missing paramters: #{missing_parameters.join(',')}" unless missing_parameters.empty?
  @relay = args[:Relay]
end

Instance Method Details

#canRetry(try) ⇒ Object 



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# File 'lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb', line 110

def canRetry( try )
  try <= MAX_RETRY
end

#dispatch(method, *args) ⇒ Object 



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# File 'lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb', line 39

def dispatch(method, *args)
  try = 0
  begin
    try += 1
    log "Dispatching call to #{method} (try #{try})"
    response = @relay.send(method,*args)
    validateResponse( response )
    return response
  rescue Exception => error
    case handleError( error,method,args )
    when :RetryWithBackoff
      retry if doBackoff( try )
    when :RetryImmediate
      retry if canRetry( try )
    when :Ignore
      return :IgnoredError => error
    when :Unknown
      raise Util::UnknownResultException.new( error, method, args )
    when :Fail
      raise error
    else
      raise "Unknown error handling method: #{handleError( error,method )}"
    end
    raise error
  end
end

#doBackoff(try) ⇒ Object 



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# File 'lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb', line 114

def doBackoff( try )
  return false unless canRetry(try)
  delay = BACKOFF_INITIAL * ( BACKOFF_BASE ** try )
  sleep delay
  return true
end

#handleError(error, method, args) ⇒ Object 



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# File 'lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb', line 73

def handleError( error, method, args )
  log "Handling error: #{error.inspect}"
  idempotent = args.none? {|params| params[:UniqueRequestToken].nil? || params[:UniqueRequestToken].empty? }
  retryable = methodRetryable( method ) || idempotent

  case error.class.to_s
  when 'Timeout::Error','SOAP::HTTPStreamError','Errno::ECONNRESET','Errno::EPIPE'
    if retryable
      return :RetryImmediate
    else
      return :Unknown
    end
  when 'SOAP::FaultError'
    case error.faultcode.data
    when "aws:Server.ServiceUnavailable"
      return :RetryWithBackoff
    else
      return :Unknown
    end
  when 'Amazon::WebServices::Util::ValidationException'
    case error.message
    when 'AWS.ServiceUnavailable'
      return :RetryWithBackoff if retryable
    end
    return :Fail
  when 'RuntimeError'
    case error.message
    when 'Throttled'
      return :RetryWithBackoff
    else
      return :RetryImmediate
    end
  else
    return :Unknown
  end
end

#isResultTag(tag) ⇒ Object 



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# File 'lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb', line 121

def isResultTag( tag )
  tag.to_s =~ RESULT_PATTERN or ACCEPTABLE_RESULTS.include?( tag.to_s )
end

#methodRetryable(method) ⇒ Object 



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# File 'lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb', line 66

def methodRetryable( method )
  RETRY_PRE.each do |pre|
    return true if method.to_s =~ /^#{pre}/i
  end
  return false
end

#validateResponse(response) ⇒ Object

Raises:



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# File 'lib/amazon/webservices/mturk/mechanical_turk_error_handler.rb', line 125

def validateResponse(response)
  log "Validating response: #{response.inspect}"
  if response[:Errors] and response[:Errors][:Error]
    if response[:Errors][:Error][:Code] == "ServiceUnavailable"
      raise 'Throttled'
    else
      raise Util::ValidationException.new(response)
    end
  end
  if response[:OperationRequest] and response[:OperationRequest][:Errors]
    raise Util::ValidationException.new(response)
  end
  resultTags = response.keys.find_all {|r| isResultTag( r ) }
  raise Util::ValidationException.new(response, "Didn't get back an acceptable result tag (got back #{response.keys.join(',')})") if resultTags.empty?
  resultTags.each do |resultTag|
    log "using result tag <#{resultTag}>"
    result = response[resultTag]
    if result[:Request] and result[:Request][:Errors]
      raise Util::ValidationException.new(result)
    end
  end
  response
end