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 7

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

Instance Method Details

#acquire ⇒ Object 



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# File 'lib/terrafying/dynamodb/named_lock.rb', line 36

def acquire
  @client.ensure_table(table) do
    begin
      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
end

#release(lock_id) ⇒ Object 



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# File 'lib/terrafying/dynamodb/named_lock.rb', line 62

def release(lock_id)
  @client.ensure_table(table) do
    begin
      @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
end

#status ⇒ Object 



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# File 'lib/terrafying/dynamodb/named_lock.rb', line 13

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

#steal ⇒ Object 



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

def steal
  @client.ensure_table(table) do
    begin
      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
end