Class: PerfectSched::SimpleDBBackend

Inherits:
Backend
  • Object
show all
Defined in:
lib/perfectsched/backend/simpledb.rb

Constant Summary collapse

MAX_SELECT_ROW = 
4

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Backend

#add, #close, #modify, #modify_data, #modify_sched

Constructor Details

#initialize(key_id, secret_key, domain) ⇒ SimpleDBBackend

Returns a new instance of SimpleDBBackend.



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# File 'lib/perfectsched/backend/simpledb.rb', line 6

def initialize(key_id, secret_key, domain)
  super()
  require 'aws-sdk'
  @consistent_read = false

  @db = AWS::SimpleDB.new(
    :access_key_id => key_id,
    :secret_access_key => secret_key)

  @domain_name = domain
  @domain = @db.domains[@domain_name]
  unless @domain.exists?
    @domain = @db.domains.create(@domain_name)
  end
end

Instance Attribute Details

#consistent_read ⇒ Object

Returns the value of attribute consistent_read.



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# File 'lib/perfectsched/backend/simpledb.rb', line 22

def consistent_read
  @consistent_read
end

Instance Method Details

#acquire(timeout, now = Time.now.to_i) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 51

def acquire(timeout, now=Time.now.to_i)
  while true
    rows = 0
    @domain.items.select('timeout', 'next_time', 'cron', 'delay', 'data',
                        :where => "timeout <= '#{int_encode(now)}'",
                        :order => [:timeout, :asc],
                        :consistent_read => @consistent_read,
                        :limit => MAX_SELECT_ROW) {|itemdata|
      begin
        id = itemdata.name
        attrs = itemdata.attributes

        @domain.items[id].attributes.replace('timeout'=>int_encode(timeout),
            :if=>{'timeout'=>attrs['timeout'].first})

        next_time = int_decode(attrs['next_time'].first)
        cron = attrs['cron'].first
        delay = int_decode(attrs['delay'].first)
        data = attrs['data'].first
        salt = int_encode(timeout)

        return [id,salt], Task.new(id, next_time, cron, delay, data)

      rescue AWS::SimpleDB::Errors::ConditionalCheckFailed, AWS::SimpleDB::Errors::AttributeDoesNotExist
      end

      rows += 1
    }
    if rows < MAX_SELECT_ROW
      return nil
    end
  end
end

#add_checked(id, cron, delay, data, next_time, timeout) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 96

def add_checked(id, cron, delay, data, next_time, timeout)
  begin
    @domain.items[id].attributes.replace('timeout'=>int_encode(timeout), 'next_time'=>int_encode(next_time),
        'cron'=>cron, 'delay'=>int_encode(delay), 'data'=>data,
        :unless=>'timeout')
    return true
  rescue AWS::SimpleDB::Errors::ConditionalCheckFailed, AWS::SimpleDB::Errors::ExistsAndExpectedValue
    return nil
  end
end

#delete(id) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 107

def delete(id)
  # TODO return value
  begin
    @domain.items[id].delete
    return true
  rescue AWS::SimpleDB::Errors::ConditionalCheckFailed, AWS::SimpleDB::Errors::AttributeDoesNotExist
    return false
  end
end

#finish(token, next_time, timeout) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 85

def finish(token, next_time, timeout)
  begin
    id, salt = *token
    @domain.items[id].attributes.replace('timeout'=>int_encode(timeout), 'next_time'=>int_encode(next_time),
        :if=>{'timeout'=>salt})
    return true
  rescue AWS::SimpleDB::Errors::ConditionalCheckFailed, AWS::SimpleDB::Errors::AttributeDoesNotExist
    return false
  end
end

#get(id) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 117

def get(id)
  attrs = @domain.items[id].data.attributes
  cron = attrs['cron'].first
  unless cron
    return nil
  end
  delay = int_decode(attrs['delay'].first)
  data = attrs['data'].first
  return cron, delay, data
end

#list(&block) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 29

def list(&block)
  rows = 0
  @domain.items.select('timeout', 'next_time', 'cron', 'delay', 'data',
                      :where => "timeout > '#{int_encode(0)}'",  # required by SimpleDB
                      :order => [:timeout, :asc],
                      :consistent_read => @consistent_read,
                      :limit => MAX_SELECT_ROW) {|itemdata|
    id = itemdata.name
    attrs = itemdata.attributes

    next_time = int_decode(attrs['next_time'].first)
    cron = attrs['cron'].first
    delay = int_decode(attrs['delay'].first)
    data = attrs['data'].first
    timeout = int_decode(attrs['timeout'].first)

    yield id, cron, delay, data, next_time, timeout
  }
end

#modify_checked(id, cron, delay, data) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 128

def modify_checked(id, cron, delay, data)
  unless get(id)
    return false
  end
  @domain.items[id].attributes.replace('cron'=>cron, 'delay'=>int_encode(delay), 'data'=>data)
  return true
end

#modify_data_checked(id, data) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 144

def modify_data_checked(id, data)
  unless get(id)
    return false
  end
  @domain.items[id].attributes.replace('data'=>data)
  return true
end

#modify_sched_checked(id, cron, delay) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 136

def modify_sched_checked(id, cron, delay)
  unless get(id)
    return false
  end
  @domain.items[id].attributes.replace('cron'=>cron, 'delay'=>int_encode(delay))
  return true
end

#use_consistent_read(b = true) ⇒ Object 



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# File 'lib/perfectsched/backend/simpledb.rb', line 24

def use_consistent_read(b=true)
  @consistent_read = b
  self
end