Class: Terrafying::DynamoDb::NamedLock

Inherits:
Object
  • Object
show all
Defined in:
lib/terrafying/dynamodb/named_lock.rb

Instance Method Summary collapse

Constructor Details

#initialize(table_name, name) ⇒ NamedLock

Returns a new instance of NamedLock.



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# File 'lib/terrafying/dynamodb/named_lock.rb', line 9

def initialize(table_name, name)
  @table_name = table_name
  @name = name
  @client = Terrafying::DynamoDb.client
end

Instance Method Details

#acquireObject



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# File 'lib/terrafying/dynamodb/named_lock.rb', line 38

def acquire
  @client.ensure_table(table) do
    lock_id = SecureRandom.uuid
    @client.update_item(acquire_request(lock_id))
    return lock_id
  rescue ::Aws::DynamoDB::Errors::ConditionalCheckFailedException
    raise "Unable to acquire lock: #{status.inspect}" # TODO
  end
end

#release(lock_id) ⇒ Object



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# File 'lib/terrafying/dynamodb/named_lock.rb', line 60

def release(lock_id)
  @client.ensure_table(table) do
    @client.delete_item(
      table_name: @table_name,
      key: {
        'name' => @name
      },
      return_values: 'NONE',
      condition_expression: 'lock_id = :lock_id',
      expression_attribute_values: {
        ':lock_id' => lock_id
      }
    )
    nil
  rescue ::Aws::DynamoDB::Errors::ConditionalCheckFailedException
    raise "Unable to release lock: #{status.inspect}" # TODO
  end
end

#statusObject



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# File 'lib/terrafying/dynamodb/named_lock.rb', line 15

def status
  @client.ensure_table(table) do
    resp = @client.get_item(
      table_name: @table_name,
      key: {
        'name' => @name
      },
      consistent_read: true
    )
    if resp.item
      return {
        status: :locked,
        locked_at: resp.item['locked_at'],
        metadata: resp.item['metadata']
      }
    else
      return {
        status: :unlocked
      }
    end
  end
end

#stealObject



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# File 'lib/terrafying/dynamodb/named_lock.rb', line 48

def steal
  @client.ensure_table(table) do
    lock_id = SecureRandom.uuid
    req = acquire_request(lock_id)
    req.delete(:condition_expression)
    @client.update_item(req)
    return lock_id
  rescue ::Aws::DynamoDB::Errors::ConditionalCheckFailedException
    raise "Unable to steal lock: #{status.inspect}" # TODO
  end
end