10 ms·

Forgive me, I'm ignorant -- what's erlang for. "Concurrent applications" is the raison d'etre I see espoused. What's that mean? Does it make concurrent applica

by MrLeap 7y ago

Forgive me, I'm ignorant -- what's erlang for. "Concurrent applications" is the raison d'etre I see espoused. What's that mean? Does it make concurrent applications easier to write? Does it make it easier to use the SIMD instruction set, how hard is it to get a function written in erlang to run on a gpu? Is it like nodejs but more performant? I appreciate anyone who has answers here, I try to position all the relatively interesting things I don't have much time to dive in to in a mental model with opportunities for future promotion.

lliamander 7y ago
Fair Question! It's not a language oriented at maximum throughput of parallel operations. It is a language that is oriented at providing very low latency (soft real-time) handling of lots of events. When you write in Erlang, you decompose your program into lots (think upwards of millions) of small user-space processes, that communicate using asynchronous messages. One side-effect of this architecture is that your application will scale in performance as you add more cores without having to change the code. It's a great language for server applications, like NodeJS. It also has a number of features that make it great for embedded and IoT type applications (which is why it was created in the first place).
- deleted 7y ago
  [deleted]
zelphirkalt 7y ago
Afaik, Erlang is all about that actor model, message passing and abstracting the lower levels away, so that ideally does not even notice that an actor is running on another machine. All of that of course with automatic restarting of failed actors. Basically it is Kubernetes done right and probably has way more functionality, as it predates all the Kubernetes stuff by a long shot and development hasn't stopped.
deleted 7y ago
[deleted]
mrkeen 7y ago
> Forgive me, I'm ignorant -- what's erlang for Since one computer can fail, your programming language should be designed to be run on multiple computers. Erlang's the only language I know about that puts this philosophy first and foremost.
- eggy 7y ago
  See https://en.wikipedia.org/wiki/Tandem_Computers https://en.wikipedia.org/wiki/Tandem_Computers This proceeded Erlang by 24 years or so. I know it's not the language, and a combination of hardware and software, but they did change the instruction set of the HP 3000 to have paged virtual memory and "share-nothing" messaging system. Also see the Pony language: https://www.ponylang.io/ https://www.ponylang.io/
  - macintux 7y ago
    Correction: about 10 years. Erlang was created in the mid-80s.
eggy 7y ago
Erlang is the functional language, but the OTP (Open Telecom Platform)is the collection of Erlang libraries or middleware that give it its concurrency prowess. It runs on the BEAM, a VM for Erlang. It goes back to 1998 or thereabouts, and was mainly implemented Ericcson by Joe Armstrong and Robert Virding and some others to handle telecom switches hence the Telecom in OTP. Joe passed away just last 20 April 2019.
- thomasfortes 7y ago
  > It goes back to 1998 or thereabouts It goes way back, 1998 was when they open sourced it, the language was in development and use inside Ericsson since 1986.
  - eggy 7y ago
    Thanks, I'm getting senile! 1986 is 8 years after my first computer. I have used Erlang's venerability in other Erlang postings, but for some reason I guess the open sourcing date stuck in my head.
gens 7y ago
Concurrency.. the way i understand it, it is about making parts of the program run independent of each other and thus can run at the same time. But you might want to check out someone who knows better, like Rob Pike: https://www.youtube.com/watch?v=cN_DpYBzKso https://www.youtube.com/watch?v=cN_DpYBzKso Yes, Erlang makes concurrent programs easier to write. Again it is better to listen to someone who knows more, like the creator of Erlang Joe Armstrong: https://www.youtube.com/watch?v=bo5WL5IQAd0 https://www.youtube.com/watch?v=bo5WL5IQAd0 Any talk by him is great. Erlang, in how i see it, makes it easier to write concurrent programs because: 1. Parts of a program communicate with other parts by passing messages 2. Every variable is static, as in if you declare that A is 12 you can not change it to be 13 Joe Armstrong had a way of explaining these things so that even i could understand, so i do recommend watching every talk you can find of him. I also recommend the interview he did of Alan Kay https://www.youtube.com/watch?v=fhOHn9TClXY https://www.youtube.com/watch?v=fhOHn9TClXY . But if you want to really get into concurrency i recommend a paper called "Communicating Sequential Processes" by C. A. R. Hoare. See http://www.usingcsp.com/ http://www.usingcsp.com/ It's a "formal language" for dealing with concurrency. Go, and some other languages, implement a "CSP style" way of doing concurrency. Erlang doesn't do SIMD, nor GPU. However, it does world scale low latency systems. Of course, it's still up to the programmer to do everything correctly and Erlang is just a tool. I don't quite like *JS, so i won't say anything about that.
derefr 7y ago
> What's that mean? "Concurrent applications" as in the C10M problem (http://c10m.robertgraham.com/p/manifesto.html http://c10m.robertgraham.com/p/manifesto.html): servers serving a lot of clients at once; usually with the added assumption of a diverse request workload (i.e. some requests are IO-bound, some are CPU-bound, some are long, some are short, etc.) • WhatsApp used Erlang (on FreeBSD) to scale 50 engineers and ~1000 boxes to handling billions of chat-message transactions per second. (https://www.infoq.com/presentations/whatsapp-scalability/ https://www.infoq.com/presentations/whatsapp-scalability/) • A lot of modern financial infrastructure (banks, exchanges, etc.) is built on Erlang. If there's a financial system that can get away with not being hard-real-time, chances are someone's considered writing it in Erlang. • Many massively-multiplayer games have Erlang in their backends or their networking middleware. • And, of course, the original point of Erlang was to route (millions of concurrent) calls in Ericsson backbone telecom routers. It can be deduced from Ericsson's continued work on Erlang's "megaco" H.248 application, that they're using Erlang in their LTE IPMS gateway appliances, to route cell-subscribers' VoLTE audio- and video-call frames. > Is it like nodejs but more performant? Node.js is decidedly bad at this type of concurrency (although its libuv is used successfully in software like Nginx—it is rather Javascript's thread-isolation semantics that bottlenecks Node.js code, not V8 as a runtime.) A better comparison is with Golang. If you put Node and Golang on a spectrum of "ability to handle highly-concurrent heterogenous workloads", then Erlang is a point much further along that spectrum than either of them. (Golang gets pretty far if the workload is homogenous, though. And you can get even further still on that spectrum with custom C or JVM code; but in the process, you'll likely sacrifice either 99th-percentile latency, or lock yourself into coding in terms of state machines. Erlang sits an an optimum where you can just write blocking code in actors and it does the right thing, predictably, even when you have millions of actors.)
- jeremyw 7y ago
  Can you say more about Go and homogeneous workloads? You might be referring to mixed IO- & CPU-bound tasks, and Go's former inability to preemptively schedule tightly written loops? (Solved along the way: https://github.com/golang/go/issues/10958 https://github.com/golang/go/issues/10958) Or something else?
lawik 7y ago
It is well suited to running concurrently as in, many cores, and in a distributed fashion, across many computers. It was built to run telephone switches and similar highly available, high performance gear in a way that is resilient to failures. Node is mostly single-threaded still, right? The Erlang VM, Beam, runs truly concurrently. Also, a few large pieces of CPU work cannot block the scheduler indefinitely. I'm not aware of a runtime that works quite like it. Suits me well. I use it throigh Elixir. It is not the fastest in any given metric from what I know but I think it delivers enormously well in real life scenarios.
lostcolony 7y ago
Probably a better description is that Erlang's raison d'etre is -fault tolerant- applications. Concurrency and distribution are just natural results of prioritizing that (because to isolate faults you need strong concurrency primitives, lest some number of bad behaving processes prevent others from being able to succeed, and you also need distribution, lest hardware faults lead to system failure). But, yeah, there are lots of good links attached. For what it means for concurrency, it's not intended to be a high performant number crunching system, but rather one built to to make concurrency safe (which ends up being extremely performant for I/O bound workloads, and extremely predictable for CPU bound ones) - M:N threading model, immutable data, shared almost nothing, achieved via the actor model.
epelesis 7y ago
Since no one has mentioned it so far, I'll go ahead and link a very insightful paper that the creator of Erlang actually wrote about how fault tolerance from the actor model make concurrent programming a breeze: https://erlang.org/download/armstrong_thesis_2003.pdf https://erlang.org/download/armstrong_thesis_2003.pdf

by MrLeap 7y ago

lliamander 7y ago

Fair Question! It's not a language oriented at maximum throughput of parallel operations. It is a language that is oriented at providing very low latency (soft real-time) handling of lots of events. When you write in Erlang, you decompose your program into lots (think upwards of millions) of small user-space processes, that communicate using asynchronous messages. One side-effect of this architecture is that your application will scale in performance as you add more cores without having to change the code. It's a great language for server applications, like NodeJS. It also has a number of features that make it great for embedded and IoT type applications (which is why it was created in the first place).

deleted 7y ago
[deleted]

zelphirkalt 7y ago

Afaik, Erlang is all about that actor model, message passing and abstracting the lower levels away, so that ideally does not even notice that an actor is running on another machine. All of that of course with automatic restarting of failed actors. Basically it is Kubernetes done right and probably has way more functionality, as it predates all the Kubernetes stuff by a long shot and development hasn't stopped.

deleted 7y ago

[deleted]

mrkeen 7y ago

> Forgive me, I'm ignorant -- what's erlang for Since one computer can fail, your programming language should be designed to be run on multiple computers. Erlang's the only language I know about that puts this philosophy first and foremost.

eggy 7y ago
See https://en.wikipedia.org/wiki/Tandem_Computers https://en.wikipedia.org/wiki/Tandem_Computers This proceeded Erlang by 24 years or so. I know it's not the language, and a combination of hardware and software, but they did change the instruction set of the HP 3000 to have paged virtual memory and "share-nothing" messaging system. Also see the Pony language: https://www.ponylang.io/ https://www.ponylang.io/
- macintux 7y ago
  Correction: about 10 years. Erlang was created in the mid-80s.

eggy 7y ago

Erlang is the functional language, but the OTP (Open Telecom Platform)is the collection of Erlang libraries or middleware that give it its concurrency prowess. It runs on the BEAM, a VM for Erlang. It goes back to 1998 or thereabouts, and was mainly implemented Ericcson by Joe Armstrong and Robert Virding and some others to handle telecom switches hence the Telecom in OTP. Joe passed away just last 20 April 2019.

thomasfortes 7y ago
> It goes back to 1998 or thereabouts It goes way back, 1998 was when they open sourced it, the language was in development and use inside Ericsson since 1986.
- eggy 7y ago
  Thanks, I'm getting senile! 1986 is 8 years after my first computer. I have used Erlang's venerability in other Erlang postings, but for some reason I guess the open sourcing date stuck in my head.

gens 7y ago

Concurrency.. the way i understand it, it is about making parts of the program run independent of each other and thus can run at the same time. But you might want to check out someone who knows better, like Rob Pike: https://www.youtube.com/watch?v=cN_DpYBzKso https://www.youtube.com/watch?v=cN_DpYBzKso Yes, Erlang makes concurrent programs easier to write. Again it is better to listen to someone who knows more, like the creator of Erlang Joe Armstrong: https://www.youtube.com/watch?v=bo5WL5IQAd0 https://www.youtube.com/watch?v=bo5WL5IQAd0 Any talk by him is great. Erlang, in how i see it, makes it easier to write concurrent programs because: 1. Parts of a program communicate with other parts by passing messages 2. Every variable is static, as in if you declare that A is 12 you can not change it to be 13 Joe Armstrong had a way of explaining these things so that even i could understand, so i do recommend watching every talk you can find of him. I also recommend the interview he did of Alan Kay https://www.youtube.com/watch?v=fhOHn9TClXY https://www.youtube.com/watch?v=fhOHn9TClXY . But if you want to really get into concurrency i recommend a paper called "Communicating Sequential Processes" by C. A. R. Hoare. See http://www.usingcsp.com/ http://www.usingcsp.com/ It's a "formal language" for dealing with concurrency. Go, and some other languages, implement a "CSP style" way of doing concurrency. Erlang doesn't do SIMD, nor GPU. However, it does world scale low latency systems. Of course, it's still up to the programmer to do everything correctly and Erlang is just a tool. I don't quite like *JS, so i won't say anything about that.

derefr 7y ago

> What's that mean? "Concurrent applications" as in the C10M problem (http://c10m.robertgraham.com/p/manifesto.html http://c10m.robertgraham.com/p/manifesto.html): servers serving a lot of clients at once; usually with the added assumption of a diverse request workload (i.e. some requests are IO-bound, some are CPU-bound, some are long, some are short, etc.) • WhatsApp used Erlang (on FreeBSD) to scale 50 engineers and ~1000 boxes to handling billions of chat-message transactions per second. (https://www.infoq.com/presentations/whatsapp-scalability/ https://www.infoq.com/presentations/whatsapp-scalability/) • A lot of modern financial infrastructure (banks, exchanges, etc.) is built on Erlang. If there's a financial system that can get away with not being hard-real-time, chances are someone's considered writing it in Erlang. • Many massively-multiplayer games have Erlang in their backends or their networking middleware. • And, of course, the original point of Erlang was to route (millions of concurrent) calls in Ericsson backbone telecom routers. It can be deduced from Ericsson's continued work on Erlang's "megaco" H.248 application, that they're using Erlang in their LTE IPMS gateway appliances, to route cell-subscribers' VoLTE audio- and video-call frames. > Is it like nodejs but more performant? Node.js is decidedly bad at this type of concurrency (although its libuv is used successfully in software like Nginx—it is rather Javascript's thread-isolation semantics that bottlenecks Node.js code, not V8 as a runtime.) A better comparison is with Golang. If you put Node and Golang on a spectrum of "ability to handle highly-concurrent heterogenous workloads", then Erlang is a point much further along that spectrum than either of them. (Golang gets pretty far if the workload is homogenous, though. And you can get even further still on that spectrum with custom C or JVM code; but in the process, you'll likely sacrifice either 99th-percentile latency, or lock yourself into coding in terms of state machines. Erlang sits an an optimum where you can just write blocking code in actors and it does the right thing, predictably, even when you have millions of actors.)

jeremyw 7y ago
Can you say more about Go and homogeneous workloads? You might be referring to mixed IO- & CPU-bound tasks, and Go's former inability to preemptively schedule tightly written loops? (Solved along the way: https://github.com/golang/go/issues/10958 https://github.com/golang/go/issues/10958) Or something else?

lawik 7y ago

It is well suited to running concurrently as in, many cores, and in a distributed fashion, across many computers. It was built to run telephone switches and similar highly available, high performance gear in a way that is resilient to failures. Node is mostly single-threaded still, right? The Erlang VM, Beam, runs truly concurrently. Also, a few large pieces of CPU work cannot block the scheduler indefinitely. I'm not aware of a runtime that works quite like it. Suits me well. I use it throigh Elixir. It is not the fastest in any given metric from what I know but I think it delivers enormously well in real life scenarios.

lostcolony 7y ago

Probably a better description is that Erlang's raison d'etre is -fault tolerant- applications. Concurrency and distribution are just natural results of prioritizing that (because to isolate faults you need strong concurrency primitives, lest some number of bad behaving processes prevent others from being able to succeed, and you also need distribution, lest hardware faults lead to system failure). But, yeah, there are lots of good links attached. For what it means for concurrency, it's not intended to be a high performant number crunching system, but rather one built to to make concurrency safe (which ends up being extremely performant for I/O bound workloads, and extremely predictable for CPU bound ones) - M:N threading model, immutable data, shared almost nothing, achieved via the actor model.

epelesis 7y ago

Since no one has mentioned it so far, I'll go ahead and link a very insightful paper that the creator of Erlang actually wrote about how fault tolerance from the actor model make concurrent programming a breeze: https://erlang.org/download/armstrong_thesis_2003.pdf https://erlang.org/download/armstrong_thesis_2003.pdf