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 14

def initialize(table_name)
  options = {}
  options[:endpoint] = ENV['AWS_DYNAMO_DB_ENDPOINT'] if ENV['AWS_DYNAMO_DB_ENDPOINT']
  @mutex      = Mutex.new
  @client     = Aws::DynamoDB::Client.new(options)
  @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 12

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 12

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 80

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 22

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

  !client.get_item(
    item_payload(ident)
  ).empty?
end

#sequence_for(ident) ⇒ Object 



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# File 'lib/alephant/sequencer/sequence_table.rb', line 30

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

  !data.empty? ? data.item['value'].to_i : 0
end

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



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# File 'lib/alephant/sequencer/sequence_table.rb', line 38

def update_sequence_id(ident, value, last_seen_check = nil)
  current_sequence = last_seen_check.nil? ? sequence_for(ident) : last_seen_check

  dynamo_response = @mutex.synchronize do
    client.put_item(
      table_name: table_name,
      item: {
        'key'   => ident,
        'value' => value
      },
      condition_expression: ':current_value < :new_value',
      expression_attribute_values: {
        ':current_value' => current_sequence,
        ':new_value'     => value
      }
    )
  end

  logger.metric('SequencerFailedConditionalChecks', value: 0)
  logger.info(
    'event'  => 'SequenceIdUpdated',
    'id'     => ident,
    'value'  => value,
    'method' => "#{self.class}#update_sequence_id"
  )

  dynamo_response

rescue Aws::DynamoDB::Errors::ConditionalCheckFailedException => e
  logger.metric 'SequencerFailedConditionalChecks'
  logger.error(
    'event'                => 'DynamoDBConditionalCheckFailed',
    'newSequenceValue'     => value,
    'currentSequenceValue' => current_sequence,
    'id'                   => ident,
    'class'                => e.class,
    'message'              => e.message,
    'backtrace'            => e.backtrace.join("\n"),
    'method'               => "#{self.class}#update_sequence_id"
  )
end