I am working on Debian and I have this server we want to monitor.
The application is ours and there are around a hundred real-time counters we want to export for monitoring purposes, graphs and alarms.
I've been looking at the Debian way of doing this because we do use Debian packaging to install the app, and Debian uses snmpd daemon, based on net-snmp, to export SNMP.
So far every approach I've seen looks very complicated, from recompiling snmpd to load a dynamic library into it, and compiling a form of subagent that replicates what snmpd does.
While all of those options make me think I should go for something else than SNMP I don't want to give up that early and I was wondering if anybody has found a feasible implementation.
Ideally it should be coded in C or C++ as the app is in C++, but I'm open to wrappers or other kind of suggestions.
net-snmp supports both the smux and agentx agent extension protocols, allowing sub-agents to live in different processes. They also have a tutorial on writing AgentX subagents in C.
An often overlooked solution is Agent++ API, which to me looks pretty nice and is under the Apache license. As far as I understand, you can modify that agent to answer to your own MIBs.
That said, doing a subagent isn't such a bad choice. You start the standard unpatched snmpd (from net-snmp). Then you connect to it with your subagent, which only adds those OIDs you want it to add. The net-snmp kit for coding AgentX (as the protocol is called) sub-agents is not dead simple to use, but not very hard either. There is also a Perl module for sub-agent development: https://metacpan.org/pod/NetSNMP::agent
The traditional way to do this in linux is to use the net-snmp package. Make sure you write the MIB first. Everything is based on the MIB and changes to the MIB usually results in lots of changes in the code. Coding for net-snmp is not difficult and there is lots of documentation to get you started, eg: http://www.net-snmp.org/wiki/index.php/Tutorials#Coding_Tutorials
Have you tried net-snmp?
Related
I've already written some backend *.dll files that I intend to use in a project. I need to visualize a simulation of the code, for which I intend to use charts and graphs from Chart.JS, by using it along with TideSDK for a desktop application.
I have no clue on how to call the C libraries via JS though. And I want to avoid creating wrapper classes in Python and going through that circuitous route. Any other options? Or are there any alternatives when trying to create an HTML/CSS/JS desktop application connected to a backend C/C++ library? Will AppJS make things easier?
TideSDK is capable of extension with modules that can be compiled and included in its runtime. It was written to be extended but I would recommend waiting for TideKit. TideSDK is a bit old and setting up a toolchain could be problematic at this point.
We've been investing in a broader vision with TideKit that is getting ready for release. You will be able to extend it with native modules and you won't need to wait too much longer to see what we've been up to. http://youtu.be/aE7gN-d0GhUthat
If you have started anything with TideSDK, you will be able to migrate your code easily to TideKit. The ability to work with with native or JavaScript modularity, and to develop for all screens from a single project code base is where all our efforts have been going.
Note that AppJS was discontinued earlier this year. An alternative is writing C extensions in node through node-webkit. Note that if you are going cross platform on this and you needed OSX as well, you cannot achieve Apple AppStore compliance with node-webkit due to private APIs as a result of its port of webkit.
I'm working on a project that needs a simple, lightweight event server (i.e. a server that passes events between different client applications implemented in Javascript). At first Node.js and Socket.io seemed like the perfect solution but the amount of dependencies and config involved took some of the shine off (see below for details on the project and why configuration is an issue). Is there some tested and reliable way to package all those dependencies into a single executable that can be run with no additional configuration? If not are there any good C/C++ Websockets libraries that could be combined with something like Mongoose to create a standalone executable?
Project Details
Basic use case:
A moderator turns on the server on their OSX machine.
A group of 10-20 users point their mobile devices to a site hosted on the moderator's machine
Communication ensues for the duration of the session (about an hour)
Basic requirements:
Simple setup: The moderator will not be a developer and may have little to no technical expertise. Anything that requires the terminal or fiddling with configuration files or package managers is a non-starter.
Unreliable Configuration: The moderator's machine will be used in a lot of different contexts and by a lot of different users. Therefore the system shouldn't rely on very specific or pristine settings (i.e. would like to avoid something with lots of dependencies that requires special environment variables to be set)
Performance and security are not a concern: The server will run locally with small number of trusted users for a short time so security and high performance aren't important.
Interesting question.
I know there are some C and/or C++ WebSocket libraries under development in the WebSocket community (mentioned on the IETF discussion list) if you want to go in that direction.
It might interest you to know that some parts of Node.js are actually written in javascript and compiled during the build process as built-in modules, but I don't know of any way to accomplish that for your own code short of hacking up the build.
Since this is OSX you could package Node alongside your own code and any modules, built against a static v8 library, in your .app. This would be a fairly tight coupling though not quite what you are asking for.
It's also possible to build your extension (or part of it) as a C++ module loaded by Node and v8.
I'm looking to create a "driver" I guess for a custom file system on physical disk for Windows. I don't exactly know the best way to explain it, but the device already has proper drivers and everything like that for Windows to communicate with it, but what I want to happen is for the user to be able to plug the device in to their PC, have it show up in My Computer, and give them full support for browsing the device.
I realize it's probably a little scary thinking about someone who doesn't know the basics of doing something like this even asking the question, but I already have classes and everything constructed for reading it within my own app... I just want everything to be more centralized and without more work from the end user. Does anyone have a good guide for creating a project like this?
The closest thing I know of to what I understand from your description is an installable file system, like the Ext2 installable file system that allows Windows computers to work with
Linux originating ext2 (and to a certain degree ext3) filesystems.
Maybe that can serve as a starting point for your investigations.
As an alternative approach there's the Shell extension which is a lot less complicated than the IFS. The now-defunct GMail shell extension used that approach, and even though it's become nonfunctional due to changes in GMail, it can still serve as inspiration.
Your options are:
Create a kernel mode file system driver. 9-12 months of work for experienced developer.
Use a framework and do everything in user mode. A couple of weeks of work to get the prototype working. The only drawback of this approach is that it's slower, than kernel-mode driver. You can play with Dokan mentioned above, or you can use our Callback File System for commercial-grade development.
I think you need to look through the Windows Driver Kit documentation (and related subjects) to figure out exactly what you're looking to create.
If you're intending to rely on the drivers that already exist, i.e. you don't need to actually execute your code in kernel land to communicate with it, I would recommend you take a look at FUSE for windows Dokan
If you indeed need to run in kernel space, and communicate directly with the hardware, you probably want to download windows DDK (driver development kit). Keep in mind that drivers for communicating with a block device and filesystems are separated, and it sound like you're talking about the filesystem itself. I believe that anything you run in kernel space will not have access to the c++ runtime, which means you can only use a subset of c++ for kernel drivers.
I want to write a C++ application with Qt, but build a prototype first using Python and then gradually replace the Python code with C++.
Is this the right approach, and what tools (bindings, binding generators, IDE) should I use?
Ideally, everything should be available in the Ubuntu repositories so I wouldn't have to worry about incompatible or old versions and have everything set up with a simple aptitude install.
Is there any comprehensive documentation about this process or do I have to learn every single component, and if yes, which ones?
Right now I have multiple choices to make:
Qt Creator, because of the nice auto completion and Qt integration.
Eclipse, as it offers support for both C++ and Python.
Eric (haven't used it yet)
Vim
PySide as it's working with CMake and Boost.Python, so theoretically it will make replacing python code easier.
PyQt as it's more widely used (more support) and is available as a Debian package.
Edit: As I will have to deploy the program to various computers, the C++-solution would require 1-5 files (the program and some library files if I'm linking it statically), using Python I'd have to build PyQt/PySide/SIP/whatever on every platform and explain how to install Python and everything else.
I want to write a C++ application with Qt, but build a prototype first using Python and then gradually replace the Python code with C++. Is this the right approach?
That depends on your goals. Having done both, I'd recommend you stay with Python wherever possible and reasonable. Although it takes a bit of discipline, it's very possible to write extremely large applications in Python. But, as you find hotspots and things that can be better handled in C++, you can certainly port relevant parts to C++.
Is there any comprehensive documentation about this process or do I have to learn every single component, and if yes, which ones?
Here's what I'd recommend for the various pieces:
EDITOR/IDE: Use any editor/IDE you're comfortable with, but I'd highly recommend one that supports refactoring. If you're comfortable with Eclipse, use it. If you want to mainly go the C++ route and you're not too familiar with any editors, you might be better off with QtCreator. Eric is an extremely good Python IDE with support for refactoring, unless you're going to be doing lots of C++, take a look at it. Even better, its source code is an example of good PyQt usage and practices.
PROCESS:
The quick summary:
Write your application in Python using PyQt
When identified as hotspots, convert decoupled Python classes to C++
Create bindings for those classes using SIP
Import the newly defined libraries in Python in place of their Python counterparts
Enjoy the speed boost
General details:
Write the application in Python using PyQt. Be careful to keep a good separation of concerns so that when you need to port pieces to C++ they will be separate from their dependencies. When you finally need to port something to C++, write it in C++/Qt and then create bindings for it using SIP. SIP has a good reference manual on the process, and you have all of PyQt as an example.
DEPLOYMENT:
C++ - For many applications the dependencies are sufficiently simple that it's not too difficult to create an installer using a tool like NullSoft's Installer or InnoSetup.
Python/PyQt - PyQt applications are a bit more difficult to install because of the dependency on Python and its dependence on the presence of the Qt libraries. One person documented his efforts on this post at ARSTechnica. py2exe works pretty well on Windows and should work fine. IME, freeze.py, which comes with the Python source, sometimes has problems determining which shared libraries are truly necessary and will sometimes end up creating a binary whose dependencies aren't present. Py2app can be made to work on Mac OS X.
But worse, however, is the PyQt/Qt licensing. If you are developing a commercial application, you need to have a commercial PyQt (and Qt) license and make sure to prevent the users from easily modifying the source or otherwise writing code against the PyQt/Qt API because of licensing restrictions. Because of that, the PyQt author created a tool called VendorId (although it has a Python license). Within VendorId is a tool called SIB that can be used to create an executable which depends only on the Python interpreter. But, if you're going to go this far, you might want to install a custom Python along with your application.
DISCLAIMER: I haven't used PySide at all, so I'm not sure how it compares to PyQt. Also, note the following warning on their website:
PySide is a work in progress and is not yet suited for application development requiring production-level stability.
But, on a good note, they intend, at least for the initial release to "maintain API compatibility with PyQt." So, aside from the C++ bindings, you could easily switch between the two later.
If you are just learning Qt and want to leverage the speed of prototyping that Python gives you, then I would recommend you make a sample project using PyQt. As you said, there is a debian package, so you are just a simple apt-get away from making your first application.
I personally use gVim as my Python/Qt editor, but you can really use any Python-friendly editor without much trouble. I liked WingIDE and they have auto-complete for Qt but once you sip from the vim kool-aid it's hard to switch.
I would say that PySide is 95%+ compatible with PyQt and the LPGL license is nice, but if you are just trying to prototype your first Qt app, then I don't think there is a real reason to use PySide. Although, I do like the PySide docs better, you can also just use them and replace all the library references with PyQt.
Depending on the complexity of the application you are building, it might be better off to just start from scratch with a C++ version than to try to do a bunch SIP refactoring black magic. Once you have a solid grasp of the Qt framework, you should be able to switch between the C++ and Python bindings pretty effortlessly.
I would draw UI mockups before starting to code prototypes. Here are some benefits:
Quicker than coding prototypes as there is no programming involved
Quickly fill widgets, such as tables and trees, with data
Add descriptions and notes to your screens
Easily integrate mockups into specification documents without having to capture screens
Validate UI design concepts before implementing
There are a lot of tools that can help you do that, but if you are going to use Qt, MockupUI may be a good choice as it renders Qt widgets with native styles for Windows 7,8 or 10 which makes your mockup look more realistic.
I want to create a web application that runs with very little RAM and I think C++ can help me achieve that.
Now, many people say C++ is unsuited for web development because:
there is no easy string manipulation
is an unsafe language (overflows, etc)
long change / build / test cycles
etc.
But I'm sure the C++ community have found ways to alleviate all those (maybe not the compile time) however since I'm not a regular so it is hard for me to put a value on what I find in Google.
So I'm asking for some guidance. I would appreciate if you share what works, what tools/libs are current and alive. What strategies can help with web dev in C++? FastCGI or embedded server (Asio / POCO / Pion / etc.)? How do you address security concerns?
Thanks a lot for any help
Have you looked at http://www.tntnet.org/. They have created a... well let me cut and paste from their website:
Tntnet is a modular, multithreaded,
high performance webapplicationserver
for C++. To create webapplications
Tntnet has a template-language called
ecpp similar to php, jsp or mason,
where you can embed c++-code inside a
html-page to generate active content.
The ecpp-files are precompiled to
c++-classes called components and
compiled and linked into a shared
library. This process is done at
compiletime.
I've used it and it has quite a small overhead plus it has screamingly fast dynamic page generation. Makes PHP, Ruby etc snails in comparison because with tntnet you are running compiled C/C++ code.
There's the Wt Project. It uses a paradigm similar to Qt's signals/slots.
There is nothing wrong with trying to build a web app in C++. It's actually a lot of fun. What you need is a:
Templating system
A CGI lib
A database API wrapper, most likely, to avoid dealing with something like the low-level MySQL API
A logger
ATL Server is a library of C++ classes that allow developers to build internet based applications.
ATL Server. It's open source too! And of course there is always ISAPI. Ah, the bad old days. :)
In your other question you mention that your embedded system is openwrt. As this router firmware already comes with a embedded web server (for it's administration UI), why don't you use that for you app as well?
Our web app backend is in C++ via CGI and we use Clearsilver templates along with the HDF that comes with it.
Give us some more hints about what you're trying to do.
You can write a good old-fashioned cgi program in C++ easily enough, and run it with FastCGI. We used to do that all the time.
You could write a C++ program embedding a lightweight HTTP server as well.
Both of them are much bigger PITAs than using something like perl or ruby.
So for why C++?
Update
Okay, got it. The main thing about FastCGI is that it avoids a fork-exec to run your CGI program, but it is a little bit different API. That's good, but you still have the problem of handling the HTTP stuff.
There are, however, several very lightweight HTTP servers, like Cherokee and Lighttpd. In similar situations (building web interfaces for appliances) I've seen people use one of these and run their C/C++ programs under them as a CGI. Lighttpd in particular seems to concentrate on making CGI-like stuff fast and efficient.
Another update. I just had cgicc pointed out to me: http://www.gnu.org/software/cgicc/
That might solve some problems.
You can try Cutelyst a C++11 built with Qt, with one of the best positions on TechEmpower Benchmarks.
Even though it requires Qt 5.6+ a full CMS (CMlyst) uses around 6MB of RAM while serving around 3000 requests per seconds on a single core.
And for your string manipulation issue QString is just an amazing class for that.