Class: Alephant::Sequencer::SequenceTable

Inherits:
Alephant::Support::DynamoDB::Table
  • Object
show all
Includes:
Logger
Defined in:
lib/alephant/sequencer/sequence_table.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(table_name) ⇒ SequenceTable

Returns a new instance of SequenceTable.



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# File 'lib/alephant/sequencer/sequence_table.rb', line 15

def initialize(table_name)
  @mutex      = Mutex.new
  @client     = AWS::DynamoDB::Client::V20120810.new
  @table_name = table_name
end

Instance Attribute Details

#client ⇒ Object (readonly)

Returns the value of attribute client.



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# File 'lib/alephant/sequencer/sequence_table.rb', line 13

def client
  @client
end

#table_name ⇒ Object (readonly)

Returns the value of attribute table_name.



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# File 'lib/alephant/sequencer/sequence_table.rb', line 13

def table_name
  @table_name
end

Instance Method Details

#delete_item!(ident) ⇒ Object 



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# File 'lib/alephant/sequencer/sequence_table.rb', line 76

def delete_item!(ident)
  client.delete_item(
    item_payload(ident)
  )
end

#sequence_exists(ident) ⇒ Object 



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# File 'lib/alephant/sequencer/sequence_table.rb', line 21

def sequence_exists(ident)
  if ident.nil?
    return false
  end

  !(client.get_item(
    item_payload(ident)
  ).length == 0)
end

#sequence_for(ident) ⇒ Object 



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# File 'lib/alephant/sequencer/sequence_table.rb', line 31

def sequence_for(ident)
  data = client.get_item(
    item_payload(ident)
  )

  data.length > 0 ? data[:item]["value"][:n].to_i : 0
end

#set_sequence_for(ident, value, last_seen_check = nil) ⇒ Object 



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# File 'lib/alephant/sequencer/sequence_table.rb', line 39

def set_sequence_for(ident, value, last_seen_check = nil)
  begin

    current_sequence = last_seen_check.nil? ? sequence_for(ident) : last_seen_check
    @mutex.synchronize do

      client.put_item({
        :table_name => table_name,
        :item => {
          'key' => {
            'S' => ident
          },
          'value' => {
            'N' => value.to_s
          }
        },
        :expected => {
          'key' => {
            :comparison_operator => 'NULL'
          },
          'value' => {
            :comparison_operator => 'GE',
            :attribute_value_list => [
              { 'N' => current_sequence.to_s }
            ]
          }
        },
        :conditional_operator => 'OR'
      })
    end

    logger.info("SequenceTable#set_sequence_for: #{value} for #{ident} success!")
  rescue AWS::DynamoDB::Errors::ConditionalCheckFailedException => e
    logger.warn("SequenceTable#set_sequence_for: (Value to put: #{value}, existing: #{current_sequence}) #{ident} outdated!")
  end
end