The Problem With Logging

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#145

There can definitely be a performance hit to overlogging, however, the decision is not a yes or no answer. When all is well, an ERROR level makes sense. Sometimes however, you may want to open the gates to DEBUG or INFO, ex. an alpha/beta release of a new feature or architecture change.

I believe the key here is flexibility, you want to have the ability to flip the switch for better forensics, but don’t want to become a slave to the data.

Interesting note, where I work, there have been more than a few ocassions where full logging would have helped isolate and track down intermittent nasties that we often see in prod but not in dev.

#146

I’m with you, Jeff, on this one about logging. I program for embedded systems and most embedded systems software are timing sensitive, so the more traces/logs, the more the logs may skew the software performance. I have many colleagues who do the info level type of trace at the start and end of a method which generates a lot of noise. I think it’s a just a lazy way of bypassing the debugger and debugging software directly from the log. Otherwise they are just copying the previous guy’s code and modifying it. Anyway I have always made it a point to question this practice when I am in the position, and the answer was always Eh, it is useful to have the trace there for debugging… Oh well, they are going to have to deal with the performance problems and the unreadability of logfile.

#147

The thing about logging is there is no right answer that is applicable for every problem.

When it comes to logging those logging hooks in your code still take time to run even when you turn that particular log off. If that’s a huge impact on your program then you are better off having debug builds and use one of those if you have a problem (or ship one to the customer when they have a problem).

When it comes to production code. I’ve got a couple of rules of thumb.

  1. Log when it’s cheap compared to the operation.
  2. Log when an exception occurs.
  3. Log when it’s really important and you need to pay the price.

If those logs aren’t enough then I use an alternative, such as conditional logs , debug builds or a debugger. Which I choose depends upon the systems constraints.

#148

Hello,

I believe the main problem with logging is that we cannot know at coding time what is going to go wrong at runtime, so we cannot know what to log … That’s why some of us end up logging everything. If you have an easy access to the running software, you can little by little log your way out of the outages, you should end up with meaningfull logs on critical parts.

DTrace and runtime weaving AOP techniques provide another way. Define what you want to log at runtime when facing the bug.

#150

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#151

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#152

At least as far as my experience goes, with embedded real time coding logging should be minimized as possible. On real time application the logging itself change the outcome. with multi threaded scenarios locking the log mechanism is a suicide. At least from my limited prospective logging other than exceptions and basic keep alive info is must NOT.
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#153

If it’s worth saving to a logfile, it’s worth showing in the user interface
Here I have a few problems, A few years back (around 2006 or so), I worked with Pharmaceutical software (21CFR-Part11 anyone?); and we used to bubble major errors to the user. Typically we’d get a call from a customer saying they had a weird bug(bear in mind this is software they’d paid millions for their couple thousand seats). Asking what it said on the screen usually turned up blanks (and often non-repeatable-yet-significant bugs turned out this way).

I’m all for bubbling up to the interface so that it can be read and noted by an intelligent user, but so far I’ve had no luck. Until that unhappy state of affairs changes, logs will have to do.

#154

After looking at the original post on stackoverflow, it appears that this comment was made with an additional caveat that you have failed to mention in your post. In fact a lot of people posting comments seem to be looking at this problem from various different perspectives.

From the original comment, I tend to be a little verbose on logging because when you have to change to debug mode, the more info you have, the better.

This poster doesn’t seem to be considering applying this level of active logging to the live system, but instead when it comes to him attempting to debug the solution. As some have commented, the log becomes a diary of what was occurring at any particular point before an error was encountered.

Maybe the question we need to ask is, The Problem With Logging As A Method Of Debugging. Since it seems that there is a common attitude amongst some developers to just as easily replace one with the other.

#155

Where the system is deployed makes a difference. A server in your data center can be subjected to probing and analysis to track down a problem. An embedded system deployed halfway across the world cannot be.

#156

I do a ton of logging during development phases, and I use a variable to determine what levels of logging I want to accomplish. When I am done developing an app, I just kill the extensive logging by changing the value of the variable.

#157

I agree with ctacke, and building in logging as needed is precisely what I do, however I use a variable to turn it off rather than having to hunt down each logging statement. I am not writing software that millions of people use, most of the software I write is to reduce manhours, so that a job previously took 100 hours now only takes a few minutes. The reduced of efficiency due to condition checking for logging really is miniscule considering the performance of the task has been time efficiency improved by a factor of over 100x in some cases.

#158

I think you only need exception plus a stack trace to solve problems, so just log those as a default.

To me, if you have logging and tracing all over the place, the application design and code is probably in rough shape, thus the need for logging.

Selective logging may come in handy in certain situations and developers should put in logging when necessary.

For example, say you have an import process where it was doing 10 major tasks, you would probably want to log what is was doing (report back to user) and you could monitor each task within the import. In cases like that it would come in useful if there was a problem.

But overall it adds clutter to the code. The performance cost is small unless you are tracing every other line of code.

I always found that using sample Debug.Write (or Trace.Write in release mode) with a debug listeners installed should be sufficient. In some cases that is not feasible due to client a restraint so a file is required. .Net comes System.Diagnotics built in, why go log crazy?

A lot of people bash log4net, but it does have the ability to define what and who gets logged, which if you have 100s of classes and lots of assemblies can help out with large scale applications.

#159

I think you only need exception plus a stack trace to solve problems, so just log those as a default.

To me, if you have logging and tracing all over the place, the application design and code is probably in rough shape, thus the need for logging.

Selective logging may come in handy in certain situations and developers should put in logging when necessary.

For example, say you have an import process where it was doing 10 major tasks, you would probably want to log what is was doing (report back to user) and you could monitor each task within the import. In cases like that it would come in useful if there was a problem.

But overall it adds clutter to the code. The performance cost is small unless you are tracing every other line of code.

I always found that using sample Debug.Write (or Trace.Write in release mode) with a debug listeners installed should be sufficient. In some cases that is not feasible due to client a restraint so a file is required. .Net comes System.Diagnotics built in, why go log crazy?

A lot of people bash log4net, but it does have the ability to define what and who gets logged, which if you have 100s of classes and lots of assemblies can help out with large scale applications.

#160

Excessive logging is really just a symptom of not doing TDD.

http://carltonnettleton.com/blog/?p=260

#161

Regarding how logging might cause deadlocks, I’m not familiar with Log4Net, but the scenario I envisage would be that some complex object has been passed to the logger, the logger has attempted to convert it to a string, and the object’s method for obtaining a string representation is doing complex stuff - maybe causing object state to be lazy-loaded from the database, that kind of thing.

#162

I have started using Aspects to weave in the log statements in the code at run time. The advantage I get is I can weave at class or package level and it allows me to switch off the logging if not required. The amount of code to be written also gets reduced by 20% leading to smaller code base and improved productivity.

#163

There is no substitute for step debugging and gleaning the code.

I recently contracted a job now that it is done. The companies on boarding wants me to write all of the tools for them. That will make their life’s as the tech support easier. That’s all fine and dandy, but me building them a bug tracking, log error reporting system, was not what I was contracted to do.

And to top that off, they want me to write so many comments, that my code will look like the incredible Hulk.

#164

@Gilbert If a tree falls in a forest, it was probably caused by logging X)

couldn’t help myself.

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#165

I completely agree with this. people get very carried away with excessive logging. Logging has to be meaningful, but to be able to create meaningful logs you need to have people who understand the meaning of logging. Excessive logging is an expensive problem, and in even in case of critical errors there is still excessive logging: You don’t need to see a 100 line stack dump when the error can be told in a single line of text. The other 99 lines are not only completely unnecessary but they’re cluttering up the screen. Log smart, log concise, log what you need to know to help the program run efficiently, not what you want know to satisfy some morbid curiosity about how the program is being used. The latter should never be the responsibility of logging. There are other systems much better suited to user activity tracking that can get a lot more detailed use-case information than logging can ever hope to accomplish.

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