The importance of trace types must be chosen not because of where the trace is in code, but because the traced message is more or less important. Example:
Trace a "Start" event when beginning a method, which should represent a single logical operation or a pipeline, along with a string representation of the parameter values passed in to the method.
Use start type when you start a logical operation. This doesn't mean that the start trace must be at the beginning of a method, nor does it mean that a method must have a start trace.
This being said, in most cases, a logical operation will actually start at the beginning of the method. Otherwise, you should ask yourself if the code is refactored correctly.
Tracing parameters may also be a bad idea. You have to think what to trace, case by case. For example it is really bad to trace parameters of a method void Authenticate(string userName, string plainPassword).
Trace an "Information" event when inserting an item into the database.
It depends. Some items must be traced, but not every item.
- For example imagine you are actually inserting a log item into your database. Would you trace logs? And then log traces? And then trace the logging of the trace?
- Another example: you're inserting a sensitive data. This requires auditing. Since you audited the insertion, why tracing it?
Trace an "Information" event when taking one path or another in an important if/else statement.
Again, it depends.
Trace a "Critical" or "Error" in a catch block depending on weather this is a recoverable error.
The action taken after a non-recoverable error can be more than tracing. For example server-side, you would like to store the exception in the database for further analysis. Also, some exceptions are less important than others, and does not require tracing.
Trace a "Stop" event when finishing the execution of the method.
See the first point.
please clarify when best to trace Verbose and Warning event types.
Verbose:
Verbose is used to trace what you need to trace when something goes really wrong. It means that in most cases, you will disable the tracing of verbose messages, but sometimes, you have to debug some parts of your code to understand why something fails on an edge case.
You usually have lots of verbose messages which let you understand really well the application flow. It also means that those messages must be disabled most of the time because:
- otherwise, the log will grow really fast,
- you don't need them most of the time,
- they may contain sensitive data about the application flow.
Think about verbose as a tool you have to use when you don't have an access to the debugger.
Warning:
Warning type trace is used when something wrong and important happens, but is not too crucial to be treated as an error. For example low RAM may emit a warning, but there is no reason to trace an error, since your application can continue, even if it will be slower than usual.
Examples:
Example 1: the application failed to open the file the user requested to open. The file exists and is not in use, permissions are set correctly, but something blocks the opening of a file. In this case, you will trace an error, since your application cannot manage this case and continue to work as expected by the user (i.e. actually read the file).
Example 2: after inspection of the error in the first example, you find that the error is caused by the fact that the file path is longer than 259 characters. So you refactor your code to catch PathTooLongException. When, the next time, the user tries to open the same file, the new version of the application shows a message explaining that the file is too long and must be moved to another folder to shorten the full path in order to open this file in this application. You also trace a message.
Example 3: your application spent twenty seconds opening and parsing a small file while most files take ten to one hundred milliseconds to open and parse. You trace a warning with relevant info: the type of disk where the file actually is, the file system, the size of the file, the exact time spent, the time the computer was on, etc. When the user complains that it takes twenty seconds to open the file, you take the trace to find what happens. You find for example that it takes so long to load the files from a network share when the computer have just started. You explain to the user that the delay is due to the network and is not related to your application.
Example 4: the opened file is displayed incorrectly. You enable verbose trace where you actually see how the data is loaded from file and then parsed, step by step.
We went for Java (Swing) plus some native parts via JNI. While the commercial demand for multiplatformness may be marginal today, the situation may be different in 5 years, and the app's (a scientific measurement app) life cycle is going to be more like 10+ years (its C++ predecessor, still used today, has source files dated 1991). As you wrote, Java beats .NET hands down in non-Windows environments, and if we ever need to switch away from Windows, it's just a matter of re-compiling some native parts, maybe fine-tuning the GUI looks, and checking that everything works.
If you're sure you'll be Windows only, and your app is going to live just few years, then .NET may be preferred - it looks and behaves more like a native app because it is. But as a long term investment I trust Java more. Swing may look a little less than perfect, the start-up time may be longer, everything is a bit sub-optimal because of the multiplatform abstraction layer, but at least it "just works".
Best Answer
Two main things in production system are:
Use some kind of a logging infrastructure. If the exception can occur during the normal operation, report it in debug level. If it is a real problem, report it in error level. Either way you will have a way to troubleshoot the system by raising the log level.
Also - when you report an exception always make sure the the entire stack trace + inner exceptions are printed.