I was told by someone with a lot of experience that there is at least one alternate way to monitor Windows OS calls, in the context of for example, creating Process Monitor-like functionality or developing an anti-virus scanner, which is not "hooking" and that this alternate method is more efficient than hooking. However, I am unsure of which alternatives to hooking there are in the context of developing a filter driver to perform this task.
No. There is no equivalent for SSDT hooking but this does't mean you can not monitor events. We have several CBs in KM which can be used for monitoring and altering the data/access rights, etc. If you're talking about AV scanner those CBs are sufficient most of the time. I think it's better to describe for what you need this. Then it's easier to say what to use instead.
side note this has be put as a comment. I think it's crazy that you have to earn more than 50 rep to be able to put comments!!! Comments are useful for better understanding the questions and clarify things. Why someone needs to have rep for that?!
I'm currently working on a Backup Application, and I have received a lot of requests for features to be added recently, and the top one of them is adding a checkbox like "Back Up when on Battery Power" like Time Machine has.
So, is there a way I can get the status of the Power Adapter (plugged in and plugged in)? I assume that if one had a Desktop Mac, like iMac, etc, I would probably just get Plugged In all the time. Therefore, I need means of detecting if the computer is a portable or not.
I assume IOKit would be a library to look at, but I simply could not find anything in the docs, that are barely existent anyways on that Framework. Then, since it is an older Carbon Framework, is there a way to register a callback that gets called when that power state changes? That way I can properly implement this checkbox's functionality.
I'd appreciate help in clarifying this subject.
IOPowerSources.h has the functions you need. Start with IOPSNotificationCreateRunLoopSource() to create a run loop source and in your callback interrogate the power source info starting with IOPSCopyPowerSourcesInfo() and working your way down. There may be better examples, but this file appears to be a reasonable demonstration of how it's done; enough to get you started.
I know blocking a website is a popular question but none of the answers I've seen address my particular situation:
I want to block a website (to be selected by the user, which must also have Admin rights, on Windows XP), without forcing her to restart her browser.
The well known technique of modifying the hosts file requires some browsers to be restarted. I want to accomplish that in a way that is browser-independent (e.g. Content Advisor works in IE but not in FF) and which doesn't require the user to restart his browser.
Please note that I am interested in knowing how to do this programmatically, so http://superuser.com or http://serverfault.com aren't really the right places for this question, as they mostly suggest tools and services, while I am interested in the underlying knowledge so that I can implement it myself.
Ideas?
Thanks.
Please note that I am interested in
knowing how to do this
programmatically, so
http://superuser.com or
http://serverfault.com aren't really
the right places for this question, as
they mostly suggest tools and
services, while I am interested in the
underlying knowledge so that I can
implement it myself.
Such tools would filter traffic by implementing a NDIS Intermediate Driver. See also this other question.
Very occasionally, despite all testing efforts, I get hit with a bug report from a customer that I simply can't reproduce in the office.
(Apologies to Jeff for the 'borrowing' of the badge)
I have a few "tools" that I can use to try and locate and fix these, but it always feels a bit like I'm knife-and-forking it:-
Asking for more and more context from the customer: (systeminfo)
Log files from our application
Ad-hoc tests with the customer to attempt to change the behaviour
Providing customer with a new build with additional diagnostics
Thinking about the problem in the bath...
Site visit (assuming customer is somewhere warm and sunny)
Are there set procedures, or other techniques than anyone uses to resolve problems like this?
One of the attributes of good debuggers, I think is that they always have a lot of weapons in their toolkit. They never seem to get "stuck" for too long and there is always something else for them to try. Some of the things I've been known to do:
ask for memory dumps
install a remote debugger on a client machine
add tracing code to builds
add logging code for debugging purposes
add performance counters
add configuration parameters to various bits of suspicious code so I can turn on and off features
rewrite and refactor suspicious code
try to replicate the issue locally on a different OS or machine
use debugging tools such as application verifier
use 3rd party load generation tools
write simulation tools in-house for load generation when the above failed
use tools like Glowcode to analyse memory leaks and performance issues
reinstall the client machine from scratch
get registry dumps and apply them locally
use registry and file watcher tools
Eventually, I find the bug just gives up out of some kind of awe at my persistence. Or the client realises that it's probably a machine or client side install or configuration issue.
Extensive logging usually helps.
The easiest way is always to see the customer in action (assuming that its readily reproducible by the customer). Oftentimes, problems arise due to issues with the customer's computer environment, conflicts with other programs, etc - these are details which you will not be able to catch on your dev rig. So a site visit might be useful; but if that's not convenient, tools like RealVNC might help as well in letting you see the customer 'do their thing'.
(watching the customer in action also allows you to catch them out in any WTF moments that they might have)
Now, if the problem is intermittent, then things get somewhat more complicated. The best way to get around this problem would be to log useful information in places where you guess problems could occur and perhaps use a tool like Splunk to index the log files during analysis. A diagnostic build (i.e. with extra logging) might be useful in this case.
I'm just in the middle of implementing an automated error reporting system that sends back to me information (currently via email although you could use a webservice) from any exception encountered by the app.
That way I get (nearly) all the information that I would do if I was sitting in front of VS2008 and it really helps me to work out what the problem is.
The customers are also usually (sorta) impressed that I know about their problem as soon as they encounter it!
Also, if you use the Application.ThreadException error handler you can send back info on unexpected exceptions too!
We use all the methods you mention progressively starting with the easiest and proceeding to the harder.
However you forget that sometimes hardware is at fault. For example, memory could be malfunctioning and some computation-intensive code will behave strangely throwing exceptions with weird diagnostics. Of cource, it works on your machine, since you don't have faulty hardware.
Experience is needed to identify such errors and insist that customer tries to install the program on another machine or does hardware check. One thing that helps greatly is good error handling - when your code throws an exception it should provide details, not just indicate that something is bad. With good error indication it's easier to identify such suspicious issues related to faulty hardware.
I think one of the most important things is the ability to ask sensible questions around what the customer has reported... More often than not they're not mentioning something that they don't see as relevant, but is actually key.
Telepathy would also be useful...
We've had good success using EurekaLog with it posting directly to FogBugz. This gets us a bug report containing a call stack, along with related system info (other processes running, memory, network details etc) and a screen shot. Occasionally customers enter further info too, which is helpful. It's certainly, in most cases, made it much easier and quicker to fix bugs.
One technique I've found useful is building an application with an integrated "diagnostic" mode (enabled by a command line switch when you launch the app). That certainly avoids the need to create custom builds with additional logging.
Otherwise, it sounds like what you're doing is as good an approach as any.
Copilot (assuming customer is somewhere cold and rainy :)
The usual procedure for this is to expect something like this will happen and add a ton of logging information. Of course you don't enable it from the beginning, but only when this happens.
Usually customers don't like to have to install a new version or some diagnostic tools. It is not their job to do your debugging. And visiting a client for cases like these is rarely an option. You must involve the client as little as possible. Changing a switch and sending you a log file is OK - anything more than this is too much.
I like the alternative of thinking the problem at the bath. I will start from trying to find out the differences between my machine and the client's configuration.
As a software engineer doing webstuff (booking/shop/member systems etc) the most important thing for us is to get as much information from the customer as possible.
Going from
it's broke!
to
it's broke! & here are screenshots of
every option I picked whilst
generating this particular report
reduces the amount of time it takes us to reproduce and fix an issue no end.
It may be obvious, but it takes a fair amount of chasing to get this kind of information from our customers sometimes! But it's worth it just for those moments you find they're not actually doing what they say they are.
I had these problems also. My solution was to add lots of logging and give the customer a debug build with all the possible debug information. Then make sure dr Watson (it was on Windows NT) created a memory dump with enough information.
After loading the memory dump in the debugger I could find out where and why it crashed.
EDIT: Oh, this obviously only works if the application terminates violently...
I think following the trail of the actions user took can lead us to the reasons of failure or selective failures. But most of the times users are at loss to precisely describe the interactions with the applications, the automatic screenshot taking (if it is desktop app. for .net app you can check Jeff's UnhandledExceptionHandler). Logging all the important action which change state of the objects can also help us in understanding it.
I don't have this problem very often, but if I did, I would use a screen sharing or recorded application to watch the user in action without having to go there (unless, as you said, it's warm and sunny and the company pays the trip).
I have recently been investigating such an issue myself. Over the course of my carrier I have learnt that, while computer systems may be complex, they are predictable so have faith that you can find the problem. My approach to these kinds of issues two fold:
1) Gather as much detailed information as possible from the customer about their failure and analyse it meticulously for patterns. Gather multiple sets of data for multiple failure occurrences to build up a clearer picture.
2) Try and reproduce the failure in house. Continue to make your system more and more similar to the customers system until you can reproduce it, the system is identical or it becomes impractical to make it more similar.
While doing this consider:
1)What differences exist between this system and other working systems.
2)What has recently changed in your product or the customers configuration that has caused the problem to start occurring.
Regards
Depending on the issue you could get WinDbg dumps, they normally give a pretty good idea of what is going on. We have diagnosed quite a few problems that weren't crashed from minidumps.
For .Net apps we also was Trace.Writeline then we can get the user to fire up DbgView and send us the output.
Its very complicated issue . I was thinking writing some procedure for this . I just made some procedure for this non-reproducible bug . it might be helpful
When the Bug accorded .. There are several factors it might to occur.
I am Sure all bugs are reproducible . I always keep eye for these kind of issues..
Get the System Information
what other process the customer did before that.
Time period it occurs . its rare or frequent
its next action happened after the issue ( its always same or different )
Find the factors for this bug ( as developer )
Find the exact position where this issue happened .
Find ALL THE SYSTEM Factors on that time
check all memory leaks or user error issue or wrong condition in code
List out all facotrs to may cause this issue.
How the each factors are affected this and wat are the data is holding those factors
Check memeory issues happened
check the customer have the current update code like yours
check all log from atleast 1 month and find any upnormal operation happened . keep on note
Just a short anecdote (hence 'community wiki'): Last week I thought it was a clever idea in a Django app to import the module pprint for pretty printing Python data only if DEBUG was True:
if settings.DEBUG:
from pprint import pprint
Then I used here and there the pprint command as debugging statement:
pprint(somevar) # show somevar on the console
After finishing the work, I tested the app with setting DEBUG=False. You can guess what happened: The site broke with HTTP500 errors all over the place, and I did not know why, because there is no traceback if DEBUG is False. I was puzzled that the errors disappeared magically, if I switched back to debug mode.
It took me 1-2 hours of putting print statements all over the code to find that the code crashes at exactly the above pprint() line. Then it took me another half an hour to convince myself to stop banging my head on the table.
Now comes the moral of the story:
Not every thing that looks like a clever idea in the first view is such savvy in the end.
An important point to look at for debugging these errors are all configuration options and platform switches your code by itself makes. This can be quite a lot more than just some user preferences. Document good, if you make an assumption about the user's platform (e.g., if you test for Win/Mac/Linux only, will your code crash on BSD or Solaris?)
Cheers,
However tough a non-reproducible problem is - we can still have a structured and strategic approach to solve them - and I can say through experience that it requires out of box thinking in 50% of the cases. Generally speaking, one can categorize the problems into different types which helps to identify what tool to be used. For example if you have a non-reproducible application crash issue or a memory issue you can use profilers and nail down the issue caused in the particular functionality.
Also, one of the most important approach is inforamation rich logging. I also use a lot of enums to describe the state of the process depending on the scenario in question. for exampe, I used like Initiated, Triggered, Running, Waiting Repaired etc to describe the schedules states and saved them to DB at different stages.
Not mentioned yet, but "directed code review" is one good solution, especially if you didn't do a proper review (at least 1 hour per 100 lines of code) before release.
I have also seen impressive demos of AppSight Suite, which is basically an advanced environment monitoring and logging tool. It allows the customer to record what happens on his machine in an extensive but fairly compact log file which you can then replay.
As many have mentioned, extensive logging, and asking the client for the log files when something goes wrong. In addition, as I worked more with web apps, I'll also provide detailed, but succinct deployment documentation (e.g., deployment steps, environmental resources that need to be set up etc).
Here are common problems I've seen that lead to the types of problem you are describing:
Environment not set up properly (e.g., missing environment variables, data sources etc).
Application not fully deployed (e.g., database schema not deployed).
Difference in operating system configuration (default character encoding being the most common culprit for me).
Most of the time, these issues can be identified through the log content.
You can use tools like Microsoft SharedView or TeamViewer to connect to remote PC and inspect problem directly on site. Of course, you'll need cooperation with customer.
Background
I'm at the planning stages of a DIY project that'll help me automate some hardware at my house. It's probably also worthwhile to mention that I've got almost no experience with web-related development.
The Basics
http://img7.imageshack.us/img7/4706/drawingo.png -- I can't seem to embed the diagram.
In order to simplify management, I want to implement my UI in the browser.
The meat of my application will reside inside a Windows service or Linux daemon; this does not mean, however, that I'm after a cross-platform solution -- I'm not tied to any particular platform, so I'll pick one (probably based on the responses that I get) and stick with it.
I would prefer to use "free" tools (e.g., LAMP/WAMP), but it's not a deal breaker.
It would be nice to be able to communicate back to the user that some action is in progress (I think AJAX would be one way to go?)
Questions
The only thing that's not entirely clear to me is the implementation of step № 3. I'd like to hear possible implementation ideas (on Windows or Linux) as to how this should be done. Hopefully some of you can share how this sort of thing is done in the real world.
Miscellaneous
As always, if there's a problem with my thinking, please point it out!
There are many people better qualified to help with step 3 so I'll leave that to them.
My question is whether is you are looking forward to learning the mess of web technologies required for the front end or consider it a necessary evil on the way to what you really want to accomplish? If the latter (and assuming you are working in C/C++) consider taking a look at WT. It's a toolkit that makes the developing the web interface seem more like a desktop gui while handling much of the ugliness for you. It could potentially cut a lot of time off your development.