This document discusses Go concurrency fundamentals including goroutines, channels, and synchronization primitives. It provides examples of using goroutines and channels for signaling between processes, timeouts, heartbeats, and implementing a load balancer. Key points covered include goroutines being lightweight processes, channel-based communication between goroutines, and using select to handle multiple channel operations.
Go is a language developed by Google with multi-core in mind. Differ from other languages, concurrency is a first-class primitive in Go. This talk covers some useful patterns for dealing with concurrency.
A talk I gave at the Golang TO Meetup. Highlighting the beautiful powers of Go with respect to concurrency, and writing concurrent programs using it.
Code at: github.com/jsimnz/concurrency-talk
Most computers today have multiple cores and processes. That means, if you really want to fully explore the capabilities of them, you must explore concurrent programming resources. Go was developed with this in mind, offering goroutines and channels.
Although concurrent programming may seem simple with Go, there are a couple of details to keep in mind, to avoid problems. In this talk, I’m going to show a couple of practical examples with goroutines and channels, and some common pitfalls
Posons-nous et profitons de ce talk pour prendre un peu de hauteur sur l’état de l’industrie tech autour de la création d’API de persistence (CRUD).
D’où venons-nous, ou allons-nous ? Pourquoi le choix entre RPC, SOAP, REST et GraphQL n’est peut-être qu’un sujet de surface qui cache un problème bien plus profond…
Youtube: https://www.youtube.com/watch?v=IskE3m3VjRY
Stuart Fettinger's 6/13/2019 Chicago Microservices Meetup Presentation -
Title: Hurry Up and GO (But Not Too Fast)
Like all programming languages, GoLang can be great in some situations - not so great in others. We weigh GO against other frameworks, focusing on real-world examples to highlight benefits and common challenges. Plus, we explore how to architect and design efficient GO applications from the start, so you can limit your long-term technical debt.
The goal for this presentation is to cover the following:
- When you should and should not use GO
- Pros and cons of the language compared to others
- Efficient architecture and design, focusing on reuse and service patterns
Go is a language developed by Google with multi-core in mind. Differ from other languages, concurrency is a first-class primitive in Go. This talk covers some useful patterns for dealing with concurrency.
A talk I gave at the Golang TO Meetup. Highlighting the beautiful powers of Go with respect to concurrency, and writing concurrent programs using it.
Code at: github.com/jsimnz/concurrency-talk
Most computers today have multiple cores and processes. That means, if you really want to fully explore the capabilities of them, you must explore concurrent programming resources. Go was developed with this in mind, offering goroutines and channels.
Although concurrent programming may seem simple with Go, there are a couple of details to keep in mind, to avoid problems. In this talk, I’m going to show a couple of practical examples with goroutines and channels, and some common pitfalls
Posons-nous et profitons de ce talk pour prendre un peu de hauteur sur l’état de l’industrie tech autour de la création d’API de persistence (CRUD).
D’où venons-nous, ou allons-nous ? Pourquoi le choix entre RPC, SOAP, REST et GraphQL n’est peut-être qu’un sujet de surface qui cache un problème bien plus profond…
Youtube: https://www.youtube.com/watch?v=IskE3m3VjRY
Stuart Fettinger's 6/13/2019 Chicago Microservices Meetup Presentation -
Title: Hurry Up and GO (But Not Too Fast)
Like all programming languages, GoLang can be great in some situations - not so great in others. We weigh GO against other frameworks, focusing on real-world examples to highlight benefits and common challenges. Plus, we explore how to architect and design efficient GO applications from the start, so you can limit your long-term technical debt.
The goal for this presentation is to cover the following:
- When you should and should not use GO
- Pros and cons of the language compared to others
- Efficient architecture and design, focusing on reuse and service patterns
New language from Google, static safe compiler, with GC and as fast as C++ or Java, syntax simpler then Python - 2 hour-long tutorial and you can start code.
In this talk Serhii will talk about Go, also known as Golang – an open source language developed at Google and used in production by companies such as Docker, Dropbox, Facebook and Google itself. Go is now heavily used as a general-purpose programming language that’s a pleasure to use and maintain. This introductory talk contains many live demos of basic language concepts, concurrency model, simple HTTP-based endpoint implementation and, of course, tests using build-in framework. This presentation will be interesting for backend engineers and DevOps to understand why Go had become so popular and how it might help to build robust and maintanable services.
Agenda of the presentation:
1. Go is not C, not Java, not anything
2. Rob Pike argument
3. Main ideas and basics
4. Concurrency model
5. Tools
6. Issues
How the Go language can be used to implement a version of the Actor Model for concurrent programming.
Talk given at the Golang UK conference, August 2016
Video: https://www.youtube.com/watch?v=yCbon_9yGVs
Introduction to memcached, a caching service designed for optimizing performance and scaling in the web stack, seen from perspective of MySQL/PHP users. Given for 2nd year students of professional bachelor in ICT at Kaho St. Lieven, Gent.
Rust
Why do you care about Rust? Who has the time to learn all these new languages? It seems like a new one is popping up every other week and this trend is growing at an exponential rate. Good news, a fair number of them are crafted really well and efficiently solve specific problems. Bad news, how do you keep up with all of this, let alone decide which languages to include in your companies technology portfolio.
Despite the challenges of all these new languages, a majority of developers are intrigued about the idea of becoming a polyglot, but don't know where to begin or don't have the time. In my polyglot travels, there is one language of late that is the sure-fire answer to the above questions, Rust.
In this talk I’ll explore the value behind becoming more polyglotic as a developer, how to pick languages to learn, and then dive deep in the the language of Rust. Which in my opinion, is hands down the best up and coming languages to learn.
About the Presenter
Anthony Broad-Crawford has been a developer since the year 2000 with a short side stint as a semi-professional poker player. Since his transition to software development Anthony has...
1. Built 8 patent receiving technologies
2. Founded two global companies
3. Been a CTO (3x), CPO (1x), and CEO (1x)
and is currently the CTO at Fooda where he manages product, user experience, and engineering. Fooda is predominantly web and mobile technology company focused on bringing great & healthy food from the best restaurant's to people while at the office.
Through his career, in production applications Anthony has used Ruby, Java, Jave (Android), Objective-C and Swift, .NET, Erlang, Scala, Node.JS, LISP, Smalltalk, and even assembly, with his recent favorite, Rust . No, not all at the same time in the same application.
Anthony now spends his time building great teams, that leverage great technology, to build great products, but still looks to codes every chance he can get :)
JavaScript has some stunning features like Closures, Prototype etc. which can help to improve the readability and maintainability of the code. However, it is not easy for inexperienced developer to consume and apply those features in day to day coding. The purpose of the presentation ‘Advanced JavaScript’ is to help a reader easily understand the concept and implementation of some advanced JavaScript features.
Back in 2015, Square and Google collaborated to launch gRPC, an open source RPC framework backed by protocol buffers and HTTP/2, based on real-world experiences operating microservices at scale. If you build microservices, you will be interested in gRPC.
This webcast covers:
- a technical overview of gRPC
- use cases and applicability in your stack
- a deep dive into the practicalities of operationalizing gRPC
A presentation of what are JavaScript Promises, what problems they solve and how to use them. Dissects some Bluebird features, the most complete Promise library available for NodeJS and browser.
New language from Google, static safe compiler, with GC and as fast as C++ or Java, syntax simpler then Python - 2 hour-long tutorial and you can start code.
In this talk Serhii will talk about Go, also known as Golang – an open source language developed at Google and used in production by companies such as Docker, Dropbox, Facebook and Google itself. Go is now heavily used as a general-purpose programming language that’s a pleasure to use and maintain. This introductory talk contains many live demos of basic language concepts, concurrency model, simple HTTP-based endpoint implementation and, of course, tests using build-in framework. This presentation will be interesting for backend engineers and DevOps to understand why Go had become so popular and how it might help to build robust and maintanable services.
Agenda of the presentation:
1. Go is not C, not Java, not anything
2. Rob Pike argument
3. Main ideas and basics
4. Concurrency model
5. Tools
6. Issues
How the Go language can be used to implement a version of the Actor Model for concurrent programming.
Talk given at the Golang UK conference, August 2016
Video: https://www.youtube.com/watch?v=yCbon_9yGVs
Introduction to memcached, a caching service designed for optimizing performance and scaling in the web stack, seen from perspective of MySQL/PHP users. Given for 2nd year students of professional bachelor in ICT at Kaho St. Lieven, Gent.
Rust
Why do you care about Rust? Who has the time to learn all these new languages? It seems like a new one is popping up every other week and this trend is growing at an exponential rate. Good news, a fair number of them are crafted really well and efficiently solve specific problems. Bad news, how do you keep up with all of this, let alone decide which languages to include in your companies technology portfolio.
Despite the challenges of all these new languages, a majority of developers are intrigued about the idea of becoming a polyglot, but don't know where to begin or don't have the time. In my polyglot travels, there is one language of late that is the sure-fire answer to the above questions, Rust.
In this talk I’ll explore the value behind becoming more polyglotic as a developer, how to pick languages to learn, and then dive deep in the the language of Rust. Which in my opinion, is hands down the best up and coming languages to learn.
About the Presenter
Anthony Broad-Crawford has been a developer since the year 2000 with a short side stint as a semi-professional poker player. Since his transition to software development Anthony has...
1. Built 8 patent receiving technologies
2. Founded two global companies
3. Been a CTO (3x), CPO (1x), and CEO (1x)
and is currently the CTO at Fooda where he manages product, user experience, and engineering. Fooda is predominantly web and mobile technology company focused on bringing great & healthy food from the best restaurant's to people while at the office.
Through his career, in production applications Anthony has used Ruby, Java, Jave (Android), Objective-C and Swift, .NET, Erlang, Scala, Node.JS, LISP, Smalltalk, and even assembly, with his recent favorite, Rust . No, not all at the same time in the same application.
Anthony now spends his time building great teams, that leverage great technology, to build great products, but still looks to codes every chance he can get :)
JavaScript has some stunning features like Closures, Prototype etc. which can help to improve the readability and maintainability of the code. However, it is not easy for inexperienced developer to consume and apply those features in day to day coding. The purpose of the presentation ‘Advanced JavaScript’ is to help a reader easily understand the concept and implementation of some advanced JavaScript features.
Back in 2015, Square and Google collaborated to launch gRPC, an open source RPC framework backed by protocol buffers and HTTP/2, based on real-world experiences operating microservices at scale. If you build microservices, you will be interested in gRPC.
This webcast covers:
- a technical overview of gRPC
- use cases and applicability in your stack
- a deep dive into the practicalities of operationalizing gRPC
A presentation of what are JavaScript Promises, what problems they solve and how to use them. Dissects some Bluebird features, the most complete Promise library available for NodeJS and browser.
JDD2014: GO! The one language you have to try in 2014 - Andrzej GrzesikPROIDEA
You live and breathe http. Most of the things you do with a computer involve it.
How many tiny little http-related utils have you already created?
Is it time to stop? By no means, we all do it.
I'd just like to encourage you to write the next one in Go.
It's a fun little language, which feels like a cross-breed between C (pointers!)
and ruby (concise, powerful syntax). But how much?
Why, yet another language, but my perl/python/.. does all the things?
Well, it does. But go has a few things that make it super sweet,
is web-scale and real fun to use!
RUM isn’t just for page level metrics anymore. Thanks to modern browser updates and new techniques we can collect real user data at the object level, finding slow page components and keeping third parties honest.
In this talk we will show you how to use Resource Timing, User Timing, and other browser tricks to time the most important components in your page. We’ll also share recipes for several of the web’s most popular third parties. This will give you a head start on measuring object level performance on your own site.
Writing concurrent program is hard; maintaining concurrent program even is a nightmare. Actually, a pattern which helps us to write good concurrent code is available, that is, using “channels” to communicate.
This talk will share the channel concept with common libraries, like threading and multiprocessing, to make concurrent code elegant.
It's the talk at PyCon TW 2017 [1] and PyCon APAC/MY 2017 [2].
[1]: https://tw.pycon.org/2017
[2]: https://pycon.my/pycon-apac-2017-program-schedule/
1. what is the different unbuffered and buffered channel?
2. how to implement a job queue in golang?
3. how to stop the worker in a container?
4. Shutdown with Sigterm Handling
5. Canceling Workers without Context
6. Graceful shutdown with worker
7. How to auto-scaling build agent?
8. How to cancel the current Job?
Akka persistence == event sourcing in 30 minutesKonrad Malawski
Akka 2.3 introduces akka-persistence, a wonderful way of implementing event-sourced applications. Let's give it a shot and see how DDD and Akka are a match made in heaven :-)
An introduction into Googles programming language Go, which had its first release in March 2012. The talk has been held at the regulars' table of the GTUG Bremen.
Lua: the world's most infuriating languagejgrahamc
Slides from a talk I gave at the Lua London Meetup on October 17: "When first confronted with Lua an experienced programmer (like me!) finds themselves infuriated by the languages little differences and hopes that can dismiss it as not worth learning :-) Later they find themselves infuriated to learn that they can't dismiss it: Lua is just too fast, too useful and too flexible. This talk will look at my experience of learning Lua and using it to send a high-altitude balloon into the stratosphere and build CloudFlare's new low latency WAF."
It's time to deprecate JavaScript. It's security model and the language itself are appalling.
As data moves into the cloud the JavaScript threat is increasing and I believe the only way to fix this is to start all over again. The 14 year old language and security model aren't up to today's threats.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
"Impact of front-end architecture on development cost", Viktor TurskyiFwdays
I have heard many times that architecture is not important for the front-end. Also, many times I have seen how developers implement features on the front-end just following the standard rules for a framework and think that this is enough to successfully launch the project, and then the project fails. How to prevent this and what approach to choose? I have launched dozens of complex projects and during the talk we will analyze which approaches have worked for me and which have not.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
Key Trends Shaping the Future of Infrastructure.pdf
Go Concurrency
1. Go Concurrency
March 27, 2013
John Graham-Cumming
www.cloudflare.com!
2. Fundamentals
• goroutines
• Very lightweight processes
• All scheduling handled internally by the Go runtime
• Unless you are CPU bound you do not have to think about
scheduling
• Channel-based communication
• The right way for goroutines to talk to each other
• Synchronization Primitives
• For when a channel is too heavyweight
• Not covered in this talk
www.cloudflare.com!
3. goroutines
• “Lightweight”
• Starting 10,000 goroutines on my MacBook Pro took 22ms
• Allocated memory increased by 3,014,000 bytes (301 bytes per
goroutine)
• https://gist.github.com/jgrahamc/5253020
• Not unusual at CloudFlare to have a single Go program
running 10,000s of goroutines with 1,000,000s of
goroutines created during life program.
• So, go yourFunc() as much as you like.
www.cloudflare.com!
4. Channels
• Quick syntax review
c := make(chan bool)– Makes an unbuffered
channel of bools
c <- x – Sends a value on the channel
<- c – Waits to receive a value on the channel
x = <- c – Waits to receive a value and stores it in x
x, ok = <- c – Waits to receive a value; ok will be
false if channel is closed and empty.
www.cloudflare.com!
5. Unbuffered channels are best
• They provide both communication and synchronization
func from(connection chan int) {!
connection <- rand.Intn(100)!
}!
!
func to(connection chan int) {!
i := <- connection!
fmt.Printf("Someone sent me %dn", i)!
}!
!
func main() {!
cpus := runtime.NumCPU()!
runtime.GOMAXPROCS(cpus)!
!
connection := make(chan int)!
go from(connection)!
go to(connection)!
}!
www.cloudflare.com!
6. Using channels for signaling
(1)
• Sometimes just closing a channel is enough
c := make(chan bool)!
!
go func() {!
!// ... do some stuff!
!close(c)!
}()!
!
// ... do some other stuff!
<- c!
www.cloudflare.com!
7. Using channels for signaling (2)
• Close a channel to coordinate multiple goroutines
func worker(start chan bool) {!
<- start!
// ... do stuff!
}!
!
func main() {!
start := make(chan bool)!
!
for i := 0; i < 100; i++ {!
go worker(start)!
}!
!
close(start)!
!
// ... all workers running now!
}!
www.cloudflare.com!
8. Select
• Select statement enables sending/receiving on multiple
channels at once
select {!
case x := <- somechan:!
// ... do stuff with x!
!
case y, ok := <- someOtherchan:!
// ... do stuff with y!
// check ok to see if someOtherChan!
// is closed!
!
case outputChan <- z:!
// ... ok z was sent!
!
default:!
// ... no one wants to communicate!
}!
www.cloudflare.com!
9. Common idiom: for/select!
for {!
select {!
case x := <- somechan:!
// ... do stuff with x!
!
case y, ok := <- someOtherchan:!
// ... do stuff with y!
// check ok to see if someOtherChan!
// is closed!
!
case outputChan <- z:!
// ... ok z was sent!
!
default:!
// ... no one wants to communicate!
}!
}!
www.cloudflare.com!
10. Using channels for signaling (4)
• Close a channel to terminate multiple goroutines
func worker(die chan bool) {!
for {!
select {!
// ... do stuff cases!
case <- die: !
return!
}!
}!
}!
!
func main() {!
die := make(chan bool)!
for i := 0; i < 100; i++ {!
go worker(die)!
}!
close(die)!
}!
www.cloudflare.com!
11. Using channels for signaling (5)
• Terminate a goroutine and verify termination
func worker(die chan bool) {!
for {!
select {!
// ... do stuff cases!
case <- die:!
// ... do termination tasks !
die <- true!
return!
}!
}!
}!
func main() {!
die := make(chan bool)!
go worker(die)!
die <- true!
<- die!
}!
www.cloudflare.com!
12. Example: unique ID service
• Just receive from id to get a unique ID
• Safe to share id channel across routines
id := make(chan string)!
!
go func() {!
var counter int64 = 0!
for {!
id <- fmt.Sprintf("%x", counter)!
counter += 1!
}!
}()!
!
x := <- id // x will be 1!
x = <- id // x will be 2!
www.cloudflare.com!
13. Example: memory recycler
func recycler(give, get chan []byte) {!
q := new(list.List)!
!
for {!
if q.Len() == 0 {!
q.PushFront(make([]byte, 100))!
}!
!
e := q.Front()!
!
select {!
case s := <-give:!
q.PushFront(s[:0])!
!
case get <- e.Value.([]byte):!
q.Remove(e)!
}!
}!
}!
www.cloudflare.com!
14. Timeout
func worker(start chan bool) {!
for {!
!timeout := time.After(30 * time.Second)!
!select {!
// ... do some stuff!
!
case <- timeout:!
return!
}!
}! func worker(start chan bool) {!
timeout := time.After(30 * time.Second)!
}!
for {!
!select {!
// ... do some stuff!
!
case <- timeout:!
return!
}!
}!
}!
www.cloudflare.com!
15. Heartbeat
func worker(start chan bool) {!
heartbeat := time.Tick(30 * time.Second)!
for {!
!select {!
// ... do some stuff!
!
case <- heartbeat:!
// ... do heartbeat stuff!
}!
}!
}!
www.cloudflare.com!
16. Example: network multiplexor
• Multiple goroutines can send on the same channel
func worker(messages chan string) {!
for {!
var msg string // ... generate a message!
messages <- msg!
}!
}!
func main() {!
messages := make(chan string)!
conn, _ := net.Dial("tcp", "example.com")!
!
for i := 0; i < 100; i++ {!
go worker(messages)!
}!
for {!
msg := <- messages!
conn.Write([]byte(msg))!
}!
}!
www.cloudflare.com!
17. Example: first of N
• Dispatch requests and get back the first one to complete
type response struct {!
resp *http.Response!
url string!
}!
!
func get(url string, r chan response ) {!
if resp, err := http.Get(url); err == nil {!
r <- response{resp, url}!
}!
}!
!
func main() {!
first := make(chan response)!
for _, url := range []string{"http://code.jquery.com/jquery-1.9.1.min.js",!
"http://cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.min.js",!
"http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js",!
"http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.9.1.min.js"} {!
go get(url, first)!
}!
!
r := <- first!
// ... do something!
}!
www.cloudflare.com!
18. range!
• Can be used to consume all values from a channel
func generator(strings chan string) {!
strings <- "Five hour's New York jet lag"!
strings <- "and Cayce Pollard wakes in Camden Town"!
strings <- "to the dire and ever-decreasing circles"!
strings <- "of disrupted circadian rhythm."!
close(strings)!
}!
!
func main() {!
strings := make(chan string)!
go generator(strings)!
!
for s := range strings {!
fmt.Printf("%s ", s)!
}!
fmt.Printf("n");!
}!
www.cloudflare.com!
19. Passing a ‘response’ channel
type work struct {!
url string!
resp chan *http.Response!
}!
!
func getter(w chan work) {!
for {!
do := <- w!
resp, _ := http.Get(do.url)!
do.resp <- resp!
}!
}!
!
func main() {!
w := make(chan work)!
!
go getter(w)!
!
resp := make(chan *http.Response)!
w <- work{"http://cdnjs.cloudflare.com/jquery/1.9.1/jquery.min.js",!
resp}!
!
r := <- resp!
}!
www.cloudflare.com!
20. Buffered channels
• Can be useful to create queues
• But make reasoning about concurrency more difficult
c := make(chan bool, 100) !
www.cloudflare.com!
21. Example: an HTTP load balancer
• Limited number of HTTP clients can make requests for
URLs
• Unlimited number of goroutines need to request URLs
and get responses
• Solution: an HTTP request load balancer
www.cloudflare.com!
22. A URL getter
type job struct {!
url string!
resp chan *http.Response!
}!
!
type worker struct {!
jobs chan *job!
count int!
}!
!
func (w *worker) getter(done chan *worker) {!
for {!
j := <- w.jobs!
resp, _ := http.Get(j.url)!
j.resp <- resp!
done <- w!
}!
}!
www.cloudflare.com!
23. A way to get URLs
func get(jobs chan *job, url string, answer chan string) {!
resp := make(chan *http.Response)!
jobs <- &job{url, resp}!
r := <- resp!
answer <- r.Request.URL.String()!
}!
!
func main() {!
jobs := balancer(10, 10)!
answer := make(chan string)!
for {!
var url string!
if _, err := fmt.Scanln(&url); err != nil {!
break!
}!
go get(jobs, url, answer)!
}!
for u := range answer {!
fmt.Printf("%sn", u)!
}!
}!
www.cloudflare.com!
24. A load balancer
func balancer(count int, depth int) chan *job {!
jobs := make(chan *job)!
done := make(chan *worker)!
workers := make([]*worker, count)!
!
for i := 0; i < count; i++ {!
workers[i] = &worker{make(chan *job,
depth), 0}!
go workers[i].getter(done)!
}!
! !
go func() {! select {!
for {! case j := <- jobsource:!
var free *worker! free.jobs <- j!
min := depth! free.count++!
for _, w := range workers {! !
if w.count < min {! case w := <- done:!
free = w! w.count—!
min = w.count! }!
}! }!
}! }()!
! !
var jobsource chan *job! return jobs!
if free != nil {! }!
jobsource = jobs!
}!
www.cloudflare.com!