I would like to run Erlang application on a centOS server for stress testing. I would like to know what I must accomplish to deploy a Erlang application before I send it to the server admin to install and run.
What will I need to tell my admin to properly run an Erlang app on a server? (Basically how can I send him a file and give him an really stupid easy instructions to install it?)
Is their a way to send my app in a executable format that the admin can easily install with? Kinda like PyPy?
How can I perform code swapping? Will the app need to be in it's code state still in order to do this?
I would appreciate any help to make this process easy. Thank you!
For anyone just passing by: Even though this is my first Erlang app, I highly recommend anyone wanting to build a easy to scale server user Erlang. The benefits are amazing, if you know how to use Erlang properly.
Cheers!
The usual way of deploying an Erlang program (I'm avoiding the word application here, as it's somewhat ambiguous in an Erlang context) involves building a release (see this for some background). A release is essentially a packaging of your Erlang code (which often consists of multiple applications - hence the ambiguity) and the parts of the runtime system required to run it. The Erlang release system was designed with code upgrades in mind.
If you are using Rebar to build your program, you may find this article helpful. In addition to describing how to build a release (the process is a bit tricky) it also explains how you can deploy an upgrade.
A similar guide is also available for users of erlang.mk. If you're not using one of them already, or a comparable build tool, I strongly encourage you to do so as it makes release handling much less painful.
You may also find the answers to this question helpful. They list some additional options.
Related
I just wonder. Is there anybody in the world, using TDD or BDD to write an OS? And is this even posible? I've tried to google it, but didn't find any kind of information.
So, guys. Is it possible to build an entire OS using TDD? And BDD?
It is possible to use TDD for most of OS development and for most of the code. It may get tricky at certain times/places due to limited testability of low-level, especially CPU/hardware-specific, code. These parts either may receive less direct test coverage (if that's OK) or can be tested in virtual machines or CPU/PC simulators.
It is definitely possible. I don't know anyone who is doing it.
As a proof point, I would point out what people are doing with test driven infrastructure with Chef and unit and behavioral testing there. For more info, see TestKitchen for Chef.
I've built a set of tools I use in my day-to-day work and I would like to make them look a bit more "professional" in order to sell them to financial institutions.
At the moment these tools are written in Perl and are executed from a DOS command line, it's extremely efficient but it doesn't look very attractive.
So, I would like to add a user interface to it but I don't really know what to use for language knowning that :
A Perl CGI interface hosted on the web is not an option since the information to be given as input is quite sensitive.
It would be ideal to sell it as a package/executable.
I don't really like the Perl/Tk interface.
I'm ok with rewritting the application in another language but I would prefere to reuse the main modules in Perl since it's very powerful with regular expressions and lists/arrays.
What would you advise me to do ?
Thanks,
Lory
If you want a non-web-based GUI, and don't like Tk, there's also Wx, which is a wrapper for the wxWidgets GUI toolkit.
However, web applications nowadays can be really easy to create (using a modern framework). Take a Mojolicious application, for example: Mojolicious carries no dependencies other than Perl 5.12.x, and provides its own web server (Hypnotoad). You can start by generating a "Lite::App", which is a simple self-contained single-file application, and then grow it to a bigger distribution later on as the need arises. It even comes with tools to convert your application to a conveniently packaged distribution that can be installed as easily as any CPAN module.
So that leaves the issue of security. User authentication, IP whitelisting, local network only... there are many ways to make a web application "for internal use only" if that's what you need.
You might just throw together a web-application prototype, and once you determine customer interest in your product, invest the substantial time in writing it as a Windows GUI application.
Continuing on from DavidO's answer, because the current web microframeworks for Perl (I prefer Dancer over his suggestion of Mojolicious, but both are good and largely equivalent) contain their own bundled web mini-servers, they also allow for the app to easily run entirely on the local machine.
Since these mini-servers default to a non-standard port (usually 3000 or 5000) by default and you can easily set them to a different port, they can be isolated by firewalls relatively easily, ensuring that nobody can connect to them remotely. You can also, of course, include and IP address check in the app and have it reject any requests that don't originate from localhost.
My guess is that the target system will be Windows. Use a RAD (Rapid Application Development) platform to develop a GUI. Examples for such a platform are Delphi or .NET with C# or VB. For bundling the Perl part, consider using a tool called perl2exe.
It doesn't sound like your scripts should require a web server. Also, consider the installation hassle. Only guessing as you're not giving much information about what your scripts are doing.
I am using the Cava packager to deploy my Perl-written tools. You can even generate an installer executable with just some mouse-clicks. It works pretty well with strawberry Perl and wxPerl on Windows.
I am going to need to set up a production server to host some Scala Lift web services and applications but I've never dealt with JavaEE/servlet technologies. Could you point to a Scala/Lift-specific HOWTO on setting up a production server or, if you don't know of such a publication, explain it in more-or-less simple way?
Lift runs on any regular servlet container; so there's nothing particularly Lift-specific you need to do when building you're environment. That being said, chapter 15 of Lift in Action should help you out with the more general case of taking a Lift application to deployment.
Hope that helps.
Not sure if you are asking this, but you can set up server with Debian Lenny to serve Lift application using this reference in the Lift wiki, with a Jetty container, and PostgreSQL database. Usually the setup varies depending on the requirements of your application (which database, etc), so eventually will need to provide more information on what you need to setup for a given environment. Apart from this, reinforcing what Tim Perret said, chapter 15 in his book is really good detailing the servlet container to choose, and deployment techniques, tools, and options.
I have been trying to decide if my web project is a candidate for implementation using PSGI, but I don't really see what good it would do for my application at this stage.
I don't really understand all the fuss. To me PSGI seems like a framework that provides a common interface between different Apache modules which lets you move your application between them. e.g Easily move your application from running on mod_perl to fastcgi, and provide the application support for running on both options.
Is that right, or have I missed something?
As I and the team I am a part of not only develop the application, but also pretty much do maintenance and setup of servers I don't see the value for us of being able to run on fastcgi, cgi, and mod_perl, we do just fine with just mod_perl.
Have I misunderstood the PSGI functionality, or is it just not suitable for my project?
Forget the Apache bit. It's a way of writing your application so that the choice of webserver becomes less relevant. At $work we switched to Plack/PSGI after finding our app running with very high CPU load after upgrading to Apache2 - benchmarking various Apache configs and NYTProf'ing were unable to determine the reason, and using PSGI and the Starman webserver worked out much better for us.
Now everything is handled in one place by our PSGI app (URL re-writes, static content, expiry headers, etc) rather than Apache configuration, so it's a) Perl, and b) easily tested via our standard /t/ scripts. Also our tests are now testing exactly what a user sees, rather than just the basic app itself.
It may well not be relevant to you if you're happy with Apache and mod_perl, and I'm sure others will be able to give much better answers, but for us not having to deal with anything Apache-related again is such a relief in itself. The ease of testing, and the ability to just stick in a Data::Dumper and see what's going on rather than wrestling with ModRewrite and friends, is a great boon.
Borrowing from a recent blog post by chromatic, Why PSGI/Plack Matters (Testing), here's what it is:
It's a good idea borrowed from Python's WSGI and Ruby's Rack but made Perlish; it's a simple formalizing of a pattern of web application development, where the entry point into the application is a function reference and the exit point is a tuple of header information and a response body.
That's it. That's as simple as it can be, and that simplicity deceives a lot of people who want to learn it.
An important benefit is, ibid.,
Given a Plack application, you don't have to deploy to a web server—even locally—to test your application as if it were deployed … Plack and TWMP (and Plack::Test) use the well-defined Plack pattern to make something which was previously difficult into something amazingly easy. They're not the first and they won't be the last, but they do demonstrate the value of Plack.
Started wrote an answer and after 50 lines I deleted it. Simply because it is impossible tell (in short) why is PSGI extremely cool. I'm new in PSGI too, but zilion things now are much easier as before in my apache/mod_perl era.
I can give you next advices:
read the Plack advent calendar - all days, step-by-step. You must understand the basic philosophy, what is good on onions and so on... :)
search CPAN for "Plack::Middleware::" - and read the first few lines in each. Here are MANY. (Really should be somewhere some short overview for each one, unfortunately don't know any faster way. Simply it is good to know, what middlewares are already developed. (For example, you sure will need the Plack::Middleware::Session, or Plack::Middleware::Static and so on...)
read about Plack::Builder (already done, when you done with the advent calendar) :)
try write some apps with it and will find than Plack is like the first sex - now you didn't understand that you could live without it.
ps:
If was here something like "Perl Oscar", will sure nominating MyiagavaSan. :)
The only place where I found informations on G-WAN web server was the project web site and it looked very much like advertisement.
What I would really know is, for someone who is proficient with C, if it is as easy to use and extend that other architectures. For now I would mostly focus on scripting abilities.
Are C scripts on GWAN easy to write ?
Can you easily update and upload new C scripts to the server (say as easily than some PHP or Java pages on other architectures) ? Do you have to restart the server when doing so ?
Can you easily extend it with third party or existing C libraries ?
Any other feedback welcome.
Well, now G-WAN is available under Linux, I am using it for more than 6 months.
The C scripts are fully-ANSI C compatible so there is no difference for any seasonned C programmer.
To update them on the server, you can edit them directly in the /csp folder (remotely via SSH) or locally on a test machine (and copy them later): G-WAN reloads scripts on-the-fly when they have been changed on disk (no server stop required).
G-WAN C scripts can use any existing library (starting with all those under /usr/lib) without any configuration or interface: you just have to write a '#pragma link' followed by the name of the library at the top of your script.
What I found really useful is the ability to edit C scripts and refresh the view in the Internet browser to see how my code works.
If there is a compilation error, then G-WAN outputs the line in the source code (just like any C compiler).
But where it enters the extraordinary area, is when you have a C script crash: here also it gives you THE LINE NUMBER IN THE SOURCE CODE (with the faulty call and the backtrace).
Kind of black-magic when you are used to Apache modules.
My experience with G-WAN and its C scripts are:
The G-WAN community is very small. Questions you have are mostly answered by its single developer.
I consider the API not mature: it's not as "clean" as Java APIs.
The limitation, but at the same time the power, of C: it's a systems programming language. So writing application logic in it must be done carefully.
You generally need to be a good developer to get good results: if you do something wrong, the server crashes fast and hard (Unix-style).
I've written some scripts now, to try out G-WAN. Overall, it's been very "productive": not much bugs and it works if you follow the guidelines and don't want to do too much funky stuff you expect it to have, like mature web servers. However, I have got the feeling I'm reinventing the wheel a lot of times.
G-WAN also support scripts written in other programming languages (C++, Objective-C, Java, etc.) so you will benefit from whatever native libraries each language implements.
For C scripts, well, the /usr/lib directory lists more than 1,500 libraries that G-WAN can re-use with a simple #pragma link "library".
I found it neat to be able to write a Web application with a part in C, another in C++ and a third one in Java!
Benchmark shown how G-wan fare poorly at handling these tests.
http://joshitech.blogspot.sg/2012/04/performance-nginx-netty-cppcms.html
I have been using G-Wan for about two years. I consider it highly stable and production ready for static files. I have a number of static sites running for over a year with no issues.
I have built some small scale dynamic sites in C with it as demos/test projects. A bittorrent tracker and a real time analytics platform both using the KV Store for data backing.
In my view building large scale dynamic sites in G-Wan is possible but only with a significant investment in development and support. G-Wan is better suited to building robust highly scalable "enterprise grade" applications than tossing something together over a weekend.
I use G-Wan for a CMS http://solicms.com but for now, I use Ruby as primary language.
I have used G-wan for some preliminary testing and it does benchmark well. I have found a few points of concern that make it so that I will not likely use it for any of my projects. I have found that it seems to cache responses for about 0.5secs to speedup the responses/second and I can't have only some of the responses hitting the application code. Also the key/value store is great for cache and temporary data storage but I'm not sure how well it will work as a real back-end storage method.