An Actor Database System for Akka - btw.informatik.uni ... · Akka: Actor Supervision Each Actor has parent, gets notified on any failure, can handle it No need to think about each

An Actor Database System for Akka

Frederic Schneider, Sebastian Schmidl

{frederic.schneider, sebastian.schmidl}@student.hpi.de

MotivationObject-Relational Impedance Mismatch

Frederic Schneider, Sebastian Schmidl, 2019-03-05


Chart 2

■ Two-tiered system layout for data-centric applications

Data tier

Application / Business logic tier




Chart 3


■ Object-relational impedance mismatch of data representation in the respective tiers

Data tier





Chart 4



■ ORM tools are an attempt to solve this challenge…

Data tier

Hibernate, Active Record,

Django ORM





Chart 5



■ ORM tools are an attempt to solve this challenge…

■ …but they don’t avoid co-locating logic of expensive computations in the data tier


Data tier

Hibernate, Active Record,

Django ORM

Stored Procedures

Actor Programming



Chart 6

State

Actor =

Behavior+

Domain Actors



Chart 7

Data Storage

Dactor =

Business Logic+

→ Dissipates object-relational impedance mismatch

Example Use-Case



Chart 8

Cast

title

description

release

film_id

star_id name

Star

Film

N

M

role

Example Use-Case



Chart 9

Cast

title

description

release

film_id

star_id name

Star

Film

N

M

role

Film (film_id)

title description release

star_id name role

FilmInfo

Cast

prepareDisplayInfo()



Chart 10

Implementation in our Framework

Film (film_id)

star_id name role


FilmInfo

Cast




Chart 11

Implementation in our Framework

Film (film_id)

star_id name role


FilmInfo

Cast


Distributed Actor Database System



Chart 12

Dactors are an application-defined scaling unit

■ Dactors are strongly encapsulated

■ Dactors can be distributed across multiple runtimes

and / or physical nodes



Chart 13

Distributed Actor Database SystemPartitioning

film_id title descr. release

1 The Predator … 14.09.2018

2 Mandy … 14.09.2018

3 The Nun … 14.09.2018

Film (3)

title Descr. Release

The Predator … 14.09.2018

star_id name Role

13 BoydHolbrook

QuinnMcKenna

75 OliviaMunn

CaseyBracket

FilmInfo

Cast


Film (2)



star_id name Role

13 BoydHolbrook

QuinnMcKenna

75 OliviaMunn

CaseyBracket

FilmInfo

Cast


Film (1)



star_id name Role

13 BoydHolbrook

QuinnMcKenna

75 OliviaMunn

CaseyBracket

FilmInfo

Cast


film_id cast_id role

1 13 QuinnMcKenna

1 75 CaseyBracket

… … …

star_id name

13 BoydHolbrook

75 OliviaMunn

… …

Film

Cast Star

EvaluationMemory Overhead Experiments



Chart 14

0

50

100

150

200

250

0 20 40 60 80 100

Used H

eap S

ize in M

B

Dataset Size in MB

ADBMS Dactors

ADBMS Relations

String Data

EvaluationQuery Performance



Chart 15

0

20

40

60

80

100

120

Late

ncy in m

s

Number of Dactors (Type A, Type B)

Point Query to Type ADactors

Insert over two Dactors

Conclusion



Chart 16

Shared runtime for storage and application logic

Large Number of Dactors for data storage feasible

We also investigated…

■ Failure Handling

■ Multi-Dactor Queries

Consistency and transactions missing

Redundant storage due to denormalization

Evaluation of multi-node deployment

Thank you!Questions? Frederic Schneider

Sebastian Schmidl

{frederic.schneider, sebastian.schmidl}@student.hpi.de

Film (film_id)


star_id name role

FilmInfo

Cast


Cast

title

description

release

film_id

star_id name

Star

Film

N

M

role

~ 500 Byte memory overhead per Dactor

■ Dactor Model eases failure handling

□ What about distributed system, messaging over the network, multiple processes and threads?

■ Single-threaded semantics inside Actors

■ Explicit messaging: we expect failures

■ Akka: Actor Supervision

□ Each Actor has parent, gets notified on any failure, can handle it

□ No need to think about each failure beforehand

Use Actor supervision for failure handling of queries

AppendixFailure Handling



Chart 18

?

AppendixMulti-Dactor Queries → Functors



Chart 19

AppendixDeclaration of Sequential Functors



Chart 20

An Actor Database System for Akka - btw.informatik.uni ... · Akka: Actor Supervision Each Actor has parent, gets notified on any failure, can handle it No need to think about each

Documents