Back to the CompletableFuture: Concurrency in Action

Back to the
CompletableFuture
Dmitry Vinnik
@DmitryVinnik dvinnik.com

What are our goals?

Goals
Concurrency and Its Forms
Misconceptions of Concurrency
Workflows: How’s and Why’s

Why Concurrency?

Multi-Core
Motivation
Microservices
CCSs

Conclusion?

Concurrency is
a New Reality

Concurrency is
a Reality

But!

What’s in it for us?

Benefits
No Idling ↑ UX
Abstraction

Only good parts, right?

Complexities
Thread
Safety
Performanc
e
Liveness
SDLC

Complex

Beneficial

Beautiful

Remind anything?

Concurrency

is like

Concurrency & Sharks

Fear

Fear Admiration

Agenda
Single
Threading
Multi
Threading
Workflows
Single
Threading
Multi
Threading
Workflows
Concurrency
in Java
Concurrency
in Java

Do I even care?

“My app is single threaded”

“It is too complicated”

“Not broken, don't touch it”

Design For Concurrency
Programming
by Coincidence
Design by
Contract
Temporal
Coupling
Immutability
&
Atomicity

Programming by
Coincidence

“Can't tell if it is broken, or
if it never worked”
Programming by Coincidence

Programming by Coincidence

Design by Contract

“Require No More,
Promise No Less”
Design by Contract
Quote from Bertrand Meyer,
“Design by Contract”

Temporal Coupling

“Do time & order matter?”
Temporal Coupling

Temporal Coupling

Agenda
Single
Threading
Multi
Threading
Workflows
Single
Threading
Multi
Threading
Workflows
Concurrency
in Java
Concurrency
in Java
Single
Threading
Multi
Threading

Multithreading

What forms can it take?

Multithreading Forms
Concurrent Form
Parallel Form
Asynchronous Form
Concurrent Form
Parallel Form
Asynchronous Form

Form: Concurrency

Form: Concurrency
Multiple
Tasks
Logically
Simultaneous
Multiple CPUs

Too Abstract?

Let’s Code Something

Goal: Develop App
Form: Concurrency

What do we need?
Form: Concurrency

Coffee, Code, Coffee, Code, Coffee, Code...
T1
Form: Concurrency

Concurrent Form
Parallel Form
Asynchronous Form
Concurrent Form
Parallel Form
Asynchronous Form
Concurrent Form
Parallel Form

Form: Parallelism
Multiple
(Sub)Tasks
Physically
Simultaneous
Multiple CPUs

Goal: Develop App
Form: Parallelism

But now
Form: Parallelism

As Ambidexter
Form: Parallelism

T1
T2
Form: Parallelism

Concurrent Form
Parallel Form
Asynchronous Form
Concurrent Form
Parallel Form
Asynchronous Form
Concurrent Form
Parallel FormParallel Form
Asynchronous Form

Fire & Forget
Non-Blocking
Multiple CPUs
Form: Parallelism

Goal: Develop App
Form: Asynchrony

Question
Form: Asynchrony

Where does coffee
come from?
Form: Asynchrony

Coffee Machine
Form: Asynchrony

T1
aT1
Form: Asynchrony

Agenda
Single
Threading
Multi
Threading
Workflows
Single
Threading
Multi
Threading
Workflows
Concurrency
in Java
Concurrency
in Java
Single
Threading
Multi
Threading
Multi
Threading
Concurrency
in Java

First...

There were
Runnable & Thread

Runnable

No Input
Runnable
No Output
No Exception

Runnable
Based
Thread
Min. 1 Main
Thread
Creation
Overhead

Then JDK5 was released

Welcome
Concurrency API

Concurrency API
ThreadLocal
Atomic
Operations
Thread Safe
Collections
And More

Concurrency API
ThreadLocal
Atomic
Operations
Thread Safe
Collections
ThreadLocal
Atomic
Operations
Thread Safe
Collections

ThreadLocal

ThreadLocal
Resource
Confinement
Memory Leaks
Global Fields

Concurrency API
ThreadLocal
Atomic
Operations
Thread Safe
Collections
ThreadLocal
Atomic
Operations
Thread Safe
Collections
ThreadLocal
Atomic
Operations

Atomic Operations

Atomic Operations
Compound
Operations
↑ Speed
Compare
& Swap

Concurrency API
ThreadLocal
Atomic
Operations
Thread Safe
Collections
ThreadLocal
Atomic
Operations
Thread Safe
Collections
ThreadLocal
Atomic
Operations
Atomic
Operations
Thread Safe
Collections
Thread Safe
Collections

Thread Safe Collections
ConcurrentHashMap

Thread Safe Collections
Compound
Operations
↑ Speed
Configurable
Concurrency

Agenda
Single
Threading
Multi
Threading
Workflows
Single
Threading
Multi
Threading
Workflows
Concurrency
in Java
Concurrency
in Java
Single
Threading
Multi
Threading
Multi
Threading
Concurrency
in Java
Concurrency
in Java
Workflows

Where do we start?

Promises in
JavaScript
Future/
Callable
Executor
Framework
Completable
Future
Workflows
Promises in
JavaScript
Future/
Callable
Executor
Framework
Completable
Future

Callback Hell
in JavaScript

Callback Hell in JavaScript
Verbose
Intuitive

How do we fix this?

Promises in JavaScript

Promises in JavaScript
Before After

Promises in
JavaScript
Future/
Callable
Executor
Framework
Completable
Future
Workflows
Promises in
JavaScript
Future/
Callable
Executor
Framework
Completable
Future
Promises in
JavaScript
Future/
Callable

Runnable -> Thread

Callable -> Future

Callable

No Input
Callable
Has Output
Has Exception

Future

Completed in
the Future
Future
Executor
Framework

Future sounds great!

But how do we use it?

Promises in
JavaScript
Future/
Callable
Executor
Framework
Completable
Future
Workflows
Promises in
JavaScript
Future/
Callable
Executor
Framework
Completable
Future
Promises in
JavaScript
Future/
Callable
Future/
Callable
Executor
Framework

Executor Framework

Executor Framework
Thread
Management
Declarative
Model

Thread Pool

Thread Pool
Thread
Management
Thread
Configuration

Too many arguments...

Factories to the rescue!

Executor Factories

Executor Factories
Single
Thread Pool
Cached
Thread Pool
Fixed
Thread Pool
Scheduled
Thread Pool
Work Stealing
Pool@DmitryVinnik dvinnik.com

Executor + Thread Pools

ExecutorService

ExecutorService
Async
Tasks
Thread
Pools

Are we done?

Future is not perfect!

Not really...

Future Pitfalls
Blocking
Operations
No Result
Chaining
Future
Combination
Exception
Handling

Blocking Result Retrieval

Blocking Result Retrieval
Blocking Get
Use Timeout

No Futures Chaining

Futures Chaining
No Workflows
Callback Hell

Futures Combination

Futures Combination
Blocking
InvokeAny
Blocking
InvokeAll()

Exception Handling

Exception Handling
Multiple
Exceptions
On Most
Operations

So many issues...

No worries!

CompletableFuture
is here to help

Promises in
JavaScript
Future/
Callable
Executor
Framework
Completable
Future
Workflows
Promises in
JavaScript
Future/
Callable
Executor
Framework
Completable
Future
Promises in
JavaScript
Future/
Callable
Future/
Callable
Executor
Framework
Executor
Framework
Completable
Future

CompletableFuture

CompletableFuture
Transformation
Composition
Chaining
Combination

Let’s handle them with
CompletableFuture!

Transformation/Chaining

Transformation/Chainin
g
Workflows
ForkJoin
Pool

Tasks Composition

Tasks Composition
Workflows
Flat Map

Controllable Futures

Controllable Futures
Completable
Timeout/
Default Value

Multiple Futures Control

Multiple Futures Control
AllOf/AnyOf
Results Not
Formatted

Tasks Combination

Tasks Combination
Collect
Results
Sync/Async

Call For Action
Embrace
Concurrency
Review Your
Application
Continue
Learning

About Speaker
Twitter: @DmitryVinnik
Blog: dvinnik.com
LinkedIn: in/dmitry-vinnik/
Email: dmitry@dvinnik.com

Back to the CompletableFuture: Concurrency in Action

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