Modern C++ Old Dog, New Tricks Todd L. Montgomery @toddlmontgomery - - PowerPoint PPT Presentation

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Modern C++ Old Dog, New Tricks Todd L. Montgomery @toddlmontgomery - - PowerPoint PPT Presentation

Jul 28, 2023 472 likes •1.61k views

StoneTor Modern C++ Old Dog, New Tricks Todd L. Montgomery @toddlmontgomery C++ is so old Languages are Tools Learning Tools is Good There are only two kinds of languages: the ones people complain about and the ones nobody uses.

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Modern C++

Old Dog, New Tricks

Todd L. Montgomery @toddlmontgomery

StoneTor

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C++ is so… old

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Languages are Tools Learning Tools is Good

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“There are only two kinds of languages: the ones people complain about and the ones nobody uses.”

— Bjarne Stroustrup

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  • Aeron and C++?
  • ReactiveSocket and C++?
  • What constitutes Modern C++?
  • What Lessons were learned?
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Aeron and C++?

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Truly modern messaging transport

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Feature Bloat & Complexity

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Not Fast Enough

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Low & Predictable Latency is key

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We are in a new world

Multi-core, Multi-socket, Cloud...

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We are in a new world

UDP, IPC, InfiniBand,
 RDMA, PCI-e Multi-core, Multi-socket, Cloud...

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Aeron is trying a new approach

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The Team

Todd Montgomery Richard Warburton Martin Thompson

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Publishers Subscribers Channel Stream

Messaging

Channel

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A library, not a framework, on which other abstractions and applications can be built

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Composable Design

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OSI layer 4 Transport for message oriented streams

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OSI Layer 4 (Transport) Services

  • 1. Connection Oriented Communication
  • 2. Reliability
  • 3. Flow Control
  • 4. Congestion Avoidance/Control
  • 5. Multiplexing
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Publisher Subscriber Subscriber Publisher

Architecture

IPC Log Buffer

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Sender Receiver Receiver Sender Publisher Subscriber Subscriber Publisher

Architecture

Media IPC Log Buffer Media (UDP, InfiniBand, PCI-e 3.0)

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Conductor Sender Receiver Conductor Receiver Sender Publisher Subscriber Subscriber Publisher Admin Events

Architecture

Admin Events Media IPC Log Buffer Media (UDP, InfiniBand, PCI-e 3.0) Function/Method Call Volatile Fields & Queues

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Client Media Driver Media Driver Conductor Sender Receiver Conductor Receiver Sender Client Publisher Conductor Conductor Subscriber Subscriber Publisher Admin Events

Architecture

Admin Events Media IPC Log Buffer IPC Ring/Broadcast Buffer Media (UDP, InfiniBand, PCI-e 3.0) Function/Method Call Volatile Fields & Queues

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C++?

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Client Media Driver Media Driver Conductor Sender Receiver Conductor Receiver Sender Client Publisher Conductor Conductor Subscriber Subscriber Publisher Admin Events

Architecture

Admin Events Media IPC Log Buffer IPC Ring/Broadcast Buffer Media (UDP, InfiniBand, PCI-e 3.0) Function/Method Call Volatile Fields & Queues

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Client Media Driver Media Driver Conductor Sender Receiver Conductor Receiver Sender Client Publisher Conductor Conductor Subscriber Subscriber Publisher Admin Events

Architecture

Admin Events Media IPC Log Buffer IPC Ring/Broadcast Buffer Media (UDP, InfiniBand, PCI-e 3.0) Function/Method Call Volatile Fields & Queues Client

  • Application API
  • Java, C, C++, C#, etc.
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The Media Driver is (currently) Java…

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… currently…

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ReactiveSocket and C++?

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Today, Asynchronous is the norm

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The Lure of Complexity The Need for Simplicity

Asynchrony

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Composition is hard

Asynchrony

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ReactiveX

http://reactivex.io/

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Observables

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Challenges

  • 1. Non-Blocking Back Pressure
  • 2. Heterogeneous Connectivity
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Dealing with Back Pressure

  • 1. Reative Streams
  • 2. RxJava 2.0
  • 3. Akka Streams
  • 4. java.util.concurrent.Flow (JEP 266)

http://www.reactive-streams.org/

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Rx Heterogeneous Connectivity

  • 1. ReactiveSocket

http://reactivesocket.io/

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C++?

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Rx Heterogeneous Connectivity

  • 1. ReactiveSocket

http://reactivesocket.io/

Protocol

  • Reactive Streams - Application API
  • Java, JS, C++, Go, etc.
  • What do you call a 1 language protocol?
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What constitutes Modern C++?

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“Within C++, there is a much smaller and cleaner language struggling to get out.” ”And no, that smaller and cleaner language is not Java or C#.”

— Bjarne Stroustrup

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Modern C++

Main Concept(s)

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Resource Ownership & Lifetime

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Scope Coupling Dependency

Resource Ownership & Lifetime

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Modern C++

  • Idioms (RAII, etc.)
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std::lock_guard std::unique_ptr std::shared_ptr

Resource Acquisition is Initialization (RAII)

http://en.cppreference.com/w/cpp/language/raii

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Other C++ Idioms

  • PImpl
  • CRTP
  • Erase-Remove
  • SFINAE*
  • …

* Substitution Failure is Not An Error

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Modern C++

  • Idioms (RAII, etc.)
  • Smart Pointers
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std::shared_ptr std::unique_ptr std::weak_ptr

Smart Pointers

http://en.cppreference.com/w/cpp/memory

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Smart Pointers

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Smart Pointers & Ownership

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Modern C++

  • Idioms (RAII, etc.)
  • Smart Pointers
  • Lambda's & Function Objects
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Lambda’s & Function Objects

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Modern C++

  • Idioms (RAII, etc.)
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
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std::atomic<bool> std::atomic_flag std::atomic<int>

Atomic Operations

http://en.cppreference.com/w/cpp/atomic

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Modern C++

  • Idioms (RAII, etc.)
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
  • Thread Support
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std::thread std::mutex std::async std::promise std::future

Thread Support

http://en.cppreference.com/w/cpp/thread

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Thread Support

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Modern C++

  • Idioms (RAII, etc.)
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
  • Thread Support
  • Move Construction/Assignment *
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Moving vs. Copying Ownership?

Move Construction/Assignment

http://en.cppreference.com/w/cpp/language/rule_of_three

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Modern C++

  • Idioms (RAII, etc.)
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
  • Thread Support
  • Move Construction/Assignment *
  • Toolchain (Build/Test)
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CMake Google Test Google Mock Google Benchmark etc.

Modern Toolchain

https://cmake.org/ https://github.com/google/googletest

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What Lessons were learned?

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Lessons - What do you think?

  • Idioms (RAII, etc.)
  • Stack Allocation
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
  • Thread Support
  • Move Construction/Assignment
  • Toolchain (Build/Test)
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Lessons

  • Idioms (RAII, etc.)
  • Stack Allocation
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
  • Thread Support
  • Move Construction/Assignment
  • Toolchain (Build/Test)
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RAII & Smart Pointers

  • Give in to Smart Pointers
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But But But… CYCLES!!!

Smart Pointers

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Dealing with “Cycles”

  • std::weak_ptr
  • std::enable_shared_from_this
  • Design them out
  • Techniques & Indirection
  • RCU / QSBR
  • Deferred & Unordered Destruction

(GCPP)

https://github.com/hsutter/gcpp

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RAII & Smart Pointers

  • Give in to Smart Pointers
  • Explicit Coupling
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RAII & Smart Pointers

  • Give in to Smart Pointers
  • Explicit Coupling
  • Explicit Scoping
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RAII & Smart Pointers

  • Give in to Smart Pointers
  • Explicit Coupling
  • Explicit Scoping
  • Explicit Dependency
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Hiding Complexity is not Dealing with Complexity

Explicit Coupling / Scope / Dependency

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Speaks to Quality Build Quality In

Explicit Coupling / Scope / Dependency

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Enforced Decoupling & Isolation….

Coupling / Scope / Dependency

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What a language provides? What a language takes away?

More Important?

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Deal with it up front Pays off massively later “If it hurts, do it more often”

Explicit Coupling / Scope / Dependency

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Lessons

  • Idioms (RAII, etc.)
  • Stack Allocation
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
  • Thread Support
  • Move Construction/Assignment
  • Toolchain (Build/Test)
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Not Needed Because Escape Analysis Value Types … ${EXCUSE}[i]

Stack Allocation (Lack of)

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Mechanism is NOT a set of “features”

Stack Allocation

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Stack Function Objects very very low cost deferred/conditional execution

Stack Allocation

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Lessons

  • Idioms (RAII, etc.)
  • Stack Allocation
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
  • Thread Support
  • Move Construction/Assignment
  • Toolchain (Build/Test)
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Move Construction/Assignment

  • Much more than you think
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Move Construction/Assignment

  • Much more than you think
  • Sometimes/Often better to copy
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Move Construction/Assignment

  • Much more than you think
  • Sometimes/Often better to copy
  • Optimization Interactions (e.g. SSO)
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Move Construction/Assignment

  • Much more than you think
  • Sometimes/Often better to copy
  • Optimization Interactions (e.g. SSO)
  • When you have to do it… why?!?
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Lessons

  • Idioms (RAII, etc.)
  • Stack Allocation
  • Smart Pointers
  • Lambda's & Function Objects
  • Atomics (std::atomic)
  • Thread Support
  • Move Construction/Assignment
  • Toolchain (Build/Test)
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Client Media Driver Media Driver Conductor Sender Receiver Conductor Receiver Sender Client Publisher Conductor Conductor Subscriber Subscriber Publisher Admin Events

Architecture

Admin Events Media IPC Log Buffer IPC Ring/Broadcast Buffer Media (UDP, InfiniBand, PCI-e 3.0) Function/Method Call Volatile Fields & Queues

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Data Structures (Shared Memory)

  • IPC Ring Buffers
  • IPC Broadcast Buffers
  • IPC Log Buffers
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Creates a


replicated persistent log


  • f messages

What Aeron does

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Log Buffer File

Term 2 Log Meta Data

Atomic & Ordered Operations

Term 1 Term 0

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Position

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Unique identification of a byte within each stream

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Publishers, Senders,
 Receivers, and Subscribers
 all keep position counters

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Position counters are the key to
 flow control and monitoring

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Statistics & Position Counters are accessible in shared memory

Atomic & Ordered Operations

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Multiple Challenges

  • Size (and Layout)
  • Memory Models (C++11 to Java)
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Size

Matters

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Size Matters (Atomics)

  • Not designed for arbitrary memory
  • Size not the same as the types
  • Concerned only with operations
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Memory Models

  • Interoperability with JMM
  • std::memory_order fit for purpose
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So… Aeron uses its own atomic

  • perations C/C++ functions

(JMM compatible)

* gcc x86_64 initially contributed by phaynes (phaynes@threatmetrix.com)

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Wrapping Up

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Languages are Tools Fit for purpose Add to your toolbox!

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“There are more useful systems developed in languages deemed awful than in languages praised for being beautiful--many more.”

— Bjarne Stroustrup (via Jason Pontin)

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https://github.com/real-logic/Aeron

Where can I find them?

https://github.com/ReactiveSocket/ reactivesocket-cpp

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Aeron: https://github.com/real-logic/Aeron ReactiveSocket: https://github.com/ReactiveSocket/reactivesocket-cpp Twitter: @toddlmontgomery

Thank You!

Questions?