I need advice on converting a desktop C++ application to a web app. (This is my first web app.) The desktop app currently has a C# GUI, but the functionality I need to use all resides in an unmanaged, non-threadsafe C++ DLL.
The web-app uses Rails, and will run on a Linux server. Mostly, it needs to pass a list of strings to the DLL and get a winnowed-down list in return. The DLL will need to run on a Windows server. It has a significant load time, so I want it to run persistently. And I'll need multiple instances to handle simultaneous requests in a timely manner. I need it to scale reasonably well. (In case it's relevant: The Windows server will be on Amazon Web Services.)
So I have to determine: (1) How to interact between Ruby and C++, and (2) how to manage concurrent requests.
Ruby to C++
I could use Ruby Extensions (perhaps with Swig or Rb++ to make it easier) to call the library from Ruby. But is that an option when they're running on separate servers?
Regardless, with the relative simplicity of the interactions, I should probably just go with HTTP requests. Right?
From what I've read, it sounds like FastCGI is the way to go. I'll just have to wrap my DLL in a process with a FastCGI interface. Is there any other option I should consider?
Multiple Processes
First I should clarify: The C++ DLL is not threadsafe. So I need the server to spawn a configurable number of processes, and route requests to an idle process (or hold it in a queue till one becomes idle).
If I've understood correctly, FastCGI in general supports this, and IIS in particular does too. (Apparently IIS doesn't support multithreaded FastCGI applications, but that's fine for me.)
So will this just be a matter of configuring the FastCGI Process Manager?
Look up ISAPI for IIS, then go Rails -> 'net -> Windows Server -> IIS -> ISAPI -> your ISAPI DLL plugin -> your HTTP webservice -> this DLL.
But that's a heck of a lot of hoops to jump through. Don't you have the source to the DLL?
If not, I would write a Windows test script which calls this DLL. Then I would writes tests that cover every single one of its behaviors. Then I would start a new project (maybe in Ruby, maybe in Gnu C++), and I would pass each one of those tests on the new project. I like to call this "extract algorithm refactor"; the result should be fresh code that does the same thing, more portably.
Related
I have 2 application running on the same machine.
Editor, is a Windows 8 application developed with WinRT and is sand-boxed. (Client)
Integrator is a C++ application for reading hardware devices over serial COM ports. (Server)
I have done a lot of searches about how to get client/server communication to work on Windows 8,
and can only find posts that say it is not possible using standard WinRT classes, etc.
What I need is a solution where by the Windows 8 application works as a client, and the standalone
executable works as a server.
Can someone please suggest a mechanism that can be used to do client/server communication.
If we cannot find a good solution for this, then we will have to resort to using files, which
I would rather not have to do.
Clarification: I am aware of the many mechanism that can be used to do client/server communication.
What I am looking for is a workaround to the problem, where the these techniques will not work on
a Windows 8 application, developed with WinRT. As the sand-boxing explicitly prohibits the client
and server being on the same host machine.
Well, the posts stating that such communication is not possible, are mostly right. There are 2 reasons, why this is prevented:
Being able to communicate to an application outside the sandbox effectively breaks the sandbox. The Windows Store app is now suddenly able to do everything the desktop application can do: access file system, registry... Windows Store apps live in a sandbox for reason - to be safe for the user.
The Windows Store app won't work after it is installed from the the store or from a package. It needs to have a desktop application installed and set up correctly as well.
I would suggest you try to move your server part to a different machine and make it a proper server. If for some reason you really can't do that, you still have the following options available:
You can use TCP/IP to connect local network resources if you remove the isolation for your Windows Store app. You will need to use CheckNetIsolation.exe, but since you already need to separately install the desktop application, this shouldn't be that much of a problem.
You can create files with a specific extension. Then register the desktop app for one extension and the Windows Store app for another extension. You can now shell execute files with these extensions to use them as a message for the other app.
Is it possible to write C++ code to interface with a server, but to be executed on client side, but on the browser instead of native?
Like, for example, imagine using open source classes so that you produce a file.
But because you don't want all this work to be done on the server, you run it on the browser.
So that the client gives a file or two or more as inputs, then the code runs on his machine, the final result is produced, then this file is uploaded to database on the server.
please see google native client project. http://code.google.com/p/nativeclient/
This is strange question.
You can prepare binaries that do task that you want done on client side and make server send proper binary to client when asked for it. Client then runs this binary and returns results to server.
It is possible if you know configurations of client machines (binaries must work on them). Also it have to be some security layer implemented - you don't want to allow every binary run on client (imagine man-in-the-middle attack when some malicious code is run on client).
I think your request contradicts with the idea behind server-side programming. The main purpose in using server-side programs is to make use of infrastructural components like database, network, etc. in a controlled manner. (The most typical usage of server-side applications are web sites with server side coding like JSP and ASP.)
Since servers are machines that are to be kept secure, a remote application should not be permitted to make changes or access filesystem freely. If you want to do changes on a server like doing database operations or reading/writing files, you should use applications that run on the server or provide interfaces like web services or web sites to remote client applications.
So there are a couple solutions when if you want to do work on the browser, then have the results posted in a server database.
First of all, you must set up your server ready for database work. I have done this using the MEAN stack, set up a MongoDB and interfaced it with the Mongoose API.
Now, for the meat of the question, there are many examples of browsers doing intensive work. The majority of these applications thought is not C++, but it is Javascript.
If you really want to focus on C++ (like i did in the past, in the time i asked this question, wanting to make something big for college), then you could do one of the following:
*Use Google Native Client (NaCl). This is a sandbox for running compiled C and C++ code in the browser efficiently and securely, independent of the user’s operating system.
*Maybe you should want to check out Emscripten, which is a framwork for translating C and C++ code to jaascript. This way, you can have your C or C++ binaries that worked, and have them translated to Javascript, in order to have them work in the browser too.
What C++ software stack do developers use to create custom fast, responsive and not very resource hungry web services?
I'd recommend you to take a look on CppCMS:
http://cppcms.com
It exactly fits the situation you had described:
performance-oriented (preferably web service) software stack
for C++ web development.
It should have a low memory footprint
work on UNIX (FreeBSD) and Linux systems
perform well under high server load and be able to handle many requests with great efficiency
[as I plan to use it in a virtual environment] where resources will be to some extent limited.
So far I have only come across Staff WSF, Boost, Poco libraries. The latter two could be used to implement a custom web server...
The problem that web server is about 2% of web development there are so much stuff to handle:
web templates
sessions
cache
forms
security-security-security - which is far from being trivial
And much more, that is why you need web frameworks.
You could write an apache module, and put all your processing code in there.
Or there's CppCMS, or Treefrog or for writing web services (not web sites) use gSOAP or Apache Axis
But ultimately, there's no "easy to use framework" because C++ developers like to build apps from smaller components. There's no Ruby-style framework, but there is all manner of libraries for handling xml or whatever, and Apache offers the http protocol bits in the module spec so you can build up your app quite happily using whatever pieces make sense to you. Now whether there's a market for bundling this up to make something easier to use is another matter.
Personally, the best web app system I wrote (for a company) used a very think web layer in the web server (IIS and ASP, but this applies to any webserver, use php for example) that did nothing except act as a gateway to pass the data from the requests through to a C++ service. The C++ service could then be written completely as a normal C++ command line server with well-defined entry points, using as thin an RPC system as possible (shared memory, but you may want to check out ZeroMQ), which not only increased security but allowed us to easily scale by shifting the services to app servers and running the web servers on different hardware. It was also really easy to test.
Here is my problem: I have a C++ application that consists of Qt GUI and quite a lot of backend code. Currently it is linked into one executable and runs on Solaris. Now, I would like to run the GUI on Windows and leave the rest of the code running on Solaris (porting it will be a huge effort). The interface between GUI and backend is pretty clean and consists of one C++ abstract class (also uses some stl containers). This is the part I would like to turn into webservice.
The problem is that our backend code is not thread safe therefore I will need to run a separate process on Solaris for every GUI on Windows. However, for performance reasons I cannot start and finish process for every request from the GUI.
This design means that I need to take care of several problems:
there must be a single point of contact for the GUI code,
the communication must happen with the instance started during first call (it should either be routed or the first call should return address of the actual server instance),
there must be some keep-alive messages sent between GUI and server process to manage lifetime of server process (server process cannot run forever).
Could you recommend a framework that would take care of these details (message routing/dispatching and lifetime management)?
You could technically configure Apache httpd to spawn a new instance per connection. The configuration also allows you to manage the time the processes stay alive when idle, and how many processes to leave running at a minimum. This would work well as long as the web service is stateless. A little weird, but technically feasible.
If you use something like gSoap, you can compile your C++ classes in Solaris directly into a gSoap mod and won't have to adapt it to any front-end like PHP or Java. It'll just plug into Apache httpd and start working.
Edit:
I just thought about it, and you could probably use HTTP 1.1 keep-alives to manage the life of the process too. Apache lets you configure how long it will allow the keep-alive to remain open, which keeps the thread/process for the connection active.
i am writing an program in c++ and i need an web interface to control the program and which will be efficient and best programming language ...
Your application will just have to listen to messages from the network that your web application would send to it.
Any web application (whatever the language) implementation could use sockets so don't worry about the details, just make sure your application manage messages that you made a protocol for.
Now, if you want to keep it all C++, you could use CPPCMS for your web application.
If it were Windows, I could advice you to register some COM component for your program. At least from ASP.NET it is easily accessible.
You could try some in-memory exchange techniques like reading/writing over a localhost socket connection. It however requires you to design some exchange protocol first.
Or data exchange via a database. You program writes/reads data from the database, the web front-end reads/writes data to the database.
You could use a framework like Thrift to communicate between a PHP/Python/Ruby/whatever webapp and a C++ daemon, or you could even go the extra mile (probably harder than just using something like Thrift) and write language bindings for the scripting language of your choice.
Either of the two options gives you the ability to write web-facing code in a language more suitable for the task while keeping the "heavy lifting" in C++.
Did you take a look at Wt? It's a widget-centric C++ framework for web applications, has a solid MVC system, an ORM, ...
The Win32 API method.
MSDN - Getting Started with Winsock:
http://msdn.microsoft.com/en-us/library/ms738545%28v=VS.85%29.aspx
(Since you didn't specify an OS, we're assuming Windows)
This is not as simple as it seems!
There is a mis-match between your C++ program (which presumibly is long running otherwise why would it need controlling) and a typical web program which starts up when it receives the http request and dies once the reply is sent.
You could possibly use one of the Java based web servers where it is possible to have a long running task.
Alternatively you could use a database or other storage as the communication medium:-
You program periodically writes it current status to a well know table, when a user invokes the control application it reads the current status and gives an appropriate set of options to the user which can then be stored in the DB, and actioned by your program the next time it polls for a request.
This works better if you have a queuing mechanism avaiable, as it can then be event driven rather than polled.
Go PHP :) Look at this Program execution Functions