Say my team is working on a polyglot project where different devs are contributing using various JVM-based (Scala, Kotlin) or dynamic languages (JavaScript, Ruby, Python) languages. As a Devops engineer I would like to know what types of languages are being used for a given project that gets run/executed with GraalVM.
Is there any support built in GraalVM SDK that I can leverage and hash out a quick script?
JVM based languages are, practically speaking, indistinguishable after they are compiled, i.e. they are all just bytecode.
As far as dynamic languages go, you can check which languages are installed (usign https://www.graalvm.org/truffle/javadoc/org/graalvm/polyglot/Engine.html#getLanguages-- for example) but that does not mean they are all (or any of them) actually used.
To check which languages are actually used during execution, one could develop a Truffle Instrument (https://www.graalvm.org/truffle/javadoc/com/oracle/truffle/api/instrumentation/TruffleInstrument.html) which would, on loading of new sources (https://www.graalvm.org/truffle/javadoc/com/oracle/truffle/api/instrumentation/LoadSourceListener.html), make a note of the language of the source (https://www.graalvm.org/truffle/javadoc/com/oracle/truffle/api/source/Source.html#getLanguage--), allowing one to check at any point which Truffle languages have been in use thus far.
I would like to provide a very simple scripting interface for a program I'm working on. My program would expose some functions that could be called from the script. I don't need much, maybe just variables, if/else, and loops. The two most popular languages seem to be lua, and python. I really do not like lua from my days of writing World of Warcraft plugins and both seem a lot more complicated than I need. What other languages are available?
Try the Ring programming language (http://ring-lang.net)
The compiler + The Virtual Machine are 15,000 lines of C code
The Ring can be embedded in C/C++ projects, extended using C/C++ code and/or used as standalone language.
The language is simple, trying to be natural, encourage organization and comes with transparent implementation. It comes with compact syntax and a group of features that enable the programmer to create natural interfaces and declarative domain-specific languages in a fraction of time. It is very small, fast and comes with smart garbage collector that puts the memory under the programmer control. It supports many programming paradigms, comes with useful and practical libraries. The language is designed for productivity and developing high quality solutions that can scale.
Learn about embedding the language from
https://en.wikibooks.org/wiki/Ring/Lessons/Embedding_Ring_Interpreter_in_C/C%2B%2B_Programs
I'm starting to dive into Erlang for the first time, and OTP is held aloft by lovers and critics alike as being the gold standard for highly available, distributed processing.
Given that OTP has been around for decades and is openly documented, why is it that other languages supporting lightweight threads/processes haven't adopted versions of their own? Are there technical/political challenges? Or does everyone just shrug and learn Erlang?
Thanks!
The largest issue is that most language runtimes don't have built-in lightweight concurrency and error isolation with exit signal propagation. Without those things you would have a really hard time properly porting OTP.
For the languages that do have the right kind of runtime, I am seeing some effort or at least plans to build OTP inspired frameworks. Cloud Haskell is the first that comes to mind. I also expect that Go and Rust will eventually have something like OTP if they don't already.
There are technical challenges, as Erlang itself is designed for the same features OTP is known for. Case in point, Basho Riak is a distributed fault-tolerant key/value store written in Erlang. One might be able to port it to Haskell or some similar functional language, but it would probably be a lot of work. Just for fun, you might look into OTP stuff written in the Elixir language.
Actually, it has been (tried).
Akka is the library which takes some OTP features and implements them in Scala for JVM.
Given the principles underlying JVM and BEAM (the Erlang VM) are very different (mainly GC, scheduling and message passing are radically different), I can't say how successful that implementation is and how many benefits of the original OTP it preserves. There's a lot of (heated) debate on that in the internets.
I want to write actor style code for embedded processors and I am trying to decide between writing everything in Erlang vs writing everything in zeromq+any language. Using zeromq looks to be very powerful in the sense that I can use any programming language and make my development a lot easier(many available libs) but then I am not sure if there is any gotcha in this power? I understand that Erlang represent actor model much better especially with OTP concepts but then it seems easy to represent similar actor model with zeromq? Am I looking at this correctly?
1.What do I really lose not using Erlang for embedded applications (where distributed processing, a power point of Erlang, is NOT required) and just build things on top a generic messaging framework like zeromq?
2.Is Erlang offering more than a coordinated messaging framework for a non-distributed embedded application?
3.What specific capabilities of Erlang could took too long to implement with zeromq?
You're comparing apples and oranges. Part of the advantage of using Erlang is the language; if you're going to put it up against zmq + some other language, the other language in that comparison really matters. zmq + ARM assembly? Erlang brings all the wonderful advantages of not hand-coding ASM.
As for what else Erlang brings to the table, Embedded Erlang? Absolutely argues that Erlang has advantages in fault tolerance, hot code loading, rapid development by leveraging Erlang and OTP, easy interaction with C libraries, and simple debugging by live REPL and copy-paste of terms.
Some of those things, such as hot reload, on-device REPL, and established libraries, will definitely take some real hacking to reproduce from the ground up.
My point would be that you will have to work very hard to get the same kind of error handling in Zmq. Erlang has some really nice built-in error handling when things begins to go bad. There has been considerable time spent in Erlang optimizing that part and making it robust.
Zmq on the other hand, is probably faster in some combinations with some languages when you make simple benchmarks. There is less overhead, so it may process messages faster than what Erlang can provide.
But chances are that you will end up re-implementing large parts of Erlang in the language of your choice. And you will probably not do a job as good as 6-10 developers working on Erlang/OTP for 15 years.
On the other hand, Erlang is not a simple language to learn. There is way more to it than just learning how to program in a functional style. Especially the concurrency patterns and failure handling can take some time getting used to.
ZeroMQ =/= Erlang covers many differences. The claim there is that ZeroMQ only provides the messaging aspect, not the light-weight processes, process monitoring and other aspects.
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I would like to know a list of the most common application/websites/solutions where Erlang is used, successfully or not.
Explaining why it is used into a specific solution instead of others programming languages would be very much appreciated, too.
Listing BAD Erlang case studies (cases in which Erlang is misused) it would be interesting, as well.
From Programming Erlang:
(source: google.com)
Many companies are using Erlang in their production systems:
• Amazon uses Erlang to implement SimpleDB, providing database services as a part
of the Amazon Elastic Compute Cloud (EC2).
• Yahoo! uses it in its social bookmarking service, Delicious, which has more than
5 million users and 150 million bookmarked URLs.
• Facebook uses Erlang to power the backend of its chat service, handling more than
100 million active users.
• WhatsApp uses Erlang to run messaging servers, achieving up to 2 million connected users per server.
• T-Mobile uses Erlang in its SMS and authentication systems.
• Motorola is using Erlang in call processing products in the public-safety industry.
• Ericsson uses Erlang in its support nodes, used in GPRS and 3G mobile networks
worldwide.
The most popular open source Erlang applications include the following:
• The 3D subdivision modeler Wings 3D, used to model and texture polygon
meshes.
• The Ejabberd system, which provides an Extensible Messaging and Presence Protocol
(XMPP) based instant messaging (IM) application server.
• The CouchDB “schema-less” document-oriented database, providing scalability
across multicore and multiserver clusters.
• The MochiWeb library that provides support for building lightweight HTTP servers.
It is used to power services such as MochiBot and MochiAds, which serve
dynamically generated content to millions of viewers daily.
• RabbitMQ, an AMQP messaging protocol implementation. AMQP is an emerging
standard for high-performance enterprise messaging.
ejabberd is one of the most well know erlang application and the one I learnt erlang with.
I think it's the one of most interesting project for learning erlang because it is really building on erlang's strength. (However some will argue that it's not OTP, but don't worry there's still a trove of great code inside...)
Why ?
An XMPP server (like ejabberd) can be seen as a high level router, routing messages between end users. Of course there are other features, but this is the most important aspect of an instant messaging server. It has to route many messages simultaneously, and handle many a lot of TCP/IP connections.
So we have 2 features:
handle many connections
route messages given some aspects of the message
These are examples where erlang shines.
handle many connections
It is very easy to build scalable non-blocking TCP/IP servers with erlang. In fact, it was designed to solve this problem.
And given it can spawn hundreds of thousand of processes (and not threads, it's a share-nothing approach, which is simpler to design), ejabberd is designed as a set of erlang processes (which can be distributed over several servers) :
client connection process
router process
chatroom process
server to server processes
All of them exchanging messages.
route messages given some aspects of the message
Another very lovable feature of erlang is pattern matching.
It is used throughout the language.
For instance, in the following :
access(moderator, _Config)-> rw;
access(participant, _Config)-> rw;
access(visitor, #config{type="public"})-> r;
access(visitor, #config{type="public_rw"})-> rw;
access(_User,_Config)-> none.
That's 5 different versions of the access function.
Erlang will select the most appropriate version given the arguments received. (Config is a structure of type #config which has a type attribute).
That means it is very easy and much clearer than chaining if/else or switch/case to make business rules.
To wrap up
Writing scalable servers, that's the whole point of erlang. Everything is designed it making this easy. On the two previous features, I'd add :
hot code upgrade
mnesia, distributed relational database (included in the base distribution)
mochiweb, on which most http erlang servers are built on
binary support (decoding and encoding binary protocol easy as ever)
a great community with great open source projects (ejabberd, couchdb but also webmachine, riak and a slew of library very easy to embed)
Fewer LOCs
There is also this article from Richard Jones. He rewrote an application from C++ to erlang: 75% fewer lines in erlang.
The list of most common applications for Erlang as been covered (CouchDb, ejabberd, RabbitMQ etc) but I would like to contribute the following.
The reason why it is used in these applications comes from the core strength of Erlang: managing application availability.
Erlang was built from ground up for the telco environment requiring that systems meet at least 5x9's availability (99.999% yearly up-time). This figure doesn't leave much room for downtime during a year! For this reason primarily, Erlang comes loaded with the following features (non-exhaustive):
Horizontal scalability (ability to distribute jobs across machine boundaries easily through seamless intra & inter machine communications). The built-in database (Mnesia) is also distributed by nature.
Vertical scalability (ability to distribute jobs across processing resources on the same machine): SMP is handled natively.
Code Hot-Swapping: the ability to update/upgrade code live during operations
Asynchronous: the real world is async so Erlang was built to account for this basic nature. One feature that contributes to this requirement: Erlang's "free" processes (>32000 can run concurrently).
Supervision: many different strategies for process supervision with restart strategies, thresholds etc. Helps recover from corner-cases/overloading more easily whilst still maintaining traces of the problems for later trouble-shooting, post-mortem analysis etc.
Resource Management: scheduling strategies, resource monitoring etc. Note that the default process scheduler operates with O(1) scaling.
Live debugging: the ability to "log" into live nodes at will helps trouble-shooting activities. Debugging can be undertaken live with full access to any process' running state. Also the built-in error reporting tools are very useful (but sometimes somewhat awkward to use).
Of course I could talk about its functional roots but this aspect is somewhat orthogonal to the main goal (high availability). The main component of the functional nature which contributes generously to the target goal is, IMO: "share nothing". This characteristic helps contain "side effects" and reduce the need for costly synchronization mechanisms.
I guess all these characteristics help extending a case for using Erlang in business critical applications.
One thing Erlang isn't really good at: processing big blocks of data.
We built a betting exchange (aka prediction market) using Erlang. We chose Erlang over some of the more traditional financial languages (C++, Java etc) because of the built-in concurrency. Markets function very similarly to telephony exchanges. Our CTO gave a talk on our use of Erlang at CTO talk.
We also use CouchDB and RabbitMQ as part of our stack.
Erlang comes from Ericsson, and is used within some of their telecoms systems.
Outside telecoms, CouchDb (a document-oriented database) is possibly the best known Erlang application so far.
Why Erlang ? From the overview (worth reading in full):
The document, view, security and
replication models, the special
purpose query language, the efficient
and robust disk layout and the
concurrent and reliable nature of the
Erlang platform are all carefully
integrated for a reliable and
efficient system.
I came across this is in the process of writing up a report: Erlang in Acoustic Ray Tracing.
It's an experience report on a research group's attempt to use Erlang for Acoustic Ray Tracing. They found that while it was easier to write the program, less buggy, etc. It scaled worse, and performed 10x slower than a comparable C program. So one spot where it may not be well suited is CPU intensive scenarios.
Do note though, that the people wrote the paper were in the stages of first learning Erlang, and may not have known the proper development procedures for CPU intensive Erlang.
Apparently, Yahoo used Erlang to make something it calls Harvester. Article about it here: http://www.ddj.com/architect/220600332
What is erlang good for?
http://beebole.com/en/blog/erlang/why-erlang/
http://www.aquabu.com/2008/2/15/erlang-pragmatic-studio-day-3-notes
http://www.reddit.com/r/programming/comments/9q0lr/erlang_and_highfrequency_trading/
(jerf's answer)
It's important to realize that Erlang's 4 parts: the language itself, the VMs(BEAM, hipe) standard libs (plus modules on github, CEAN, etc.) and development environment are being steadily updated / expanded/improved. For example, i remember reading that the floating point performance improved when Wings3d's author realized it needed to improve (I can't find a source for this). And this guy just wrote about it:
http://marian-dan.com/wordpress/?p=324
A couple years ago, Tim Bray's Wide Finder publicity and all the folks starting to do web app frameworks and HTTP servers lead (at least in part) to improved regex and binaries handling. And there's all the work integrating HiPE and SMP, the dialyzer project, multiple unit testing and build libs springing up, ..
So its sweet spot is expanding, The difficult thing is that the official docs can't keep up very well, and the mailing list and erlang blogosphere volume are growing quickly
We are using Erlang to provide the back-end muscle power for our really real-time browser-based multi-player game Pixza. We don't use Flash or any other third-party plugins, though the game is real-time multi-player. We use pure JS and COMET techniques instead. And Erlang supports the "really realtimeliness" of Pixza.
I'm working for wooga, a social game company and we use Erlang for some of our game backends (basically http apis for millions of daily users) and auxiliary services like ios push notification provider, payment etc.
I think it really shines in network related tasks and it makes it kind of straight forward to structure and implement simple and complex network services alike in it. Distribution, fault tolerance and performance are easy to achieve because Erlang already has some of the key ingredients built in and they are being used for a long time in critical production infrastructure. So its not like "the new hip technology thing 0.0.2 alpha".
I know that other game companies use Erlang as well. You should be able to find presentations on slideshare about that.
Erlang draws its strength from being a functional language with no shared memory. Hence IMO, Erlang won't be suitable for applications that require in place memory manipulations. Image editing for example.