I've got a method in my class only for testing purpose :
private void printOut(String msg, Object value)
{
System.out.println(msg + value);
}
It is a wrapper method for System.out.println();
So I hope, with the use of Annotation, I can choose not to run this method during productive environment while still keep those diagnostic output ready if I am to switch back to debugging environment.
Which Annotation shall I put on top of the method name?
As I stated above you should use logging.
Here are some of the benefits of using logging in an application:
Logging can generate detailed information about the operation of an application.
Once added to an application, logging requires no human intervention.
Application logs can be saved and studied at a later time.
If sufficiently detailed and properly formatted, application logs can provide audit trails.
By capturing errors that may not be reported to users, logging can help support staff with troubleshooting.
By capturing very detailed and programmer-specified messages, logging can help programmers with debugging.
Logging can be a debugging tool where debuggers are not available, which is often the case with multi-threaded or distributed applications.
Logging stays with the application and can be used anytime the application is run.
Read more about logging here
There are a lot of logging frameworks in java:
Log4j
java.util.logging
Logback.
And several facades, which provides abstraction for various logging frameworks:
slf4j
commons-logging
One solution is to use AspectJ to do this, as you can control the behavior based on annotations.
Here is a tutorial on how to use annotations as join points:
http://www.eclipse.org/aspectj//doc/next/adk15notebook/annotations-pointcuts-and-advice.html
What you could do is to have:
#DebugMessage
private void printOut(String msg, Object value)
{ }
Then, in your aspect you could have the aspect do the println call.
This way, in production, the aspect isn't included, but, should you ever need to have this active, then just add the aspect, even to production code, to get some debugging.
You should really follow uthark's advice and use a logging framework.
Those have been specifically designed for this situation.
Doing something "funky" will probably cause problems later on.
Related
We are planning to use open-telemetry as the logging tool in a new Spring-boot based micro-service. We have explored two ways to use otel, first is using manual instrumentation provided by Java and other is using Spring-cloud-sleuth using #NewSpan annotation
However, I could not find a way to specify different logging levels like INFO/ERROR/DEBUG. We need to have an ability to control and restrict the excessive logging. However, additional debug logs can help in troubleshooting if required.
How can we set the logging levels with open-telemetry java or spring-sleuth?
Uodate: As commented by #Jan , I was getting confused between tracing and logging. However, I can not find any documentation about support for logging with opentelemetry-java. Is there any way to do it? Also, if we use different tools for tracing and logging, will it be considered a bad practice?
So generally how do we use combination of tracing and logging? Can we use different frameworks for both? For example, if we use open-telemetry for tracing and slf4j/log4j for logging, will it be considered a bad practice?
OpenTelemetry will never have a "logging" API meant to be used by ordinary users, it is supposed to capture logs produced by actual logging libraries (like log4j or logback).
OpenTelemetry support for logs is still in the alpha state (meaning that the logging SPI/SDK might still change in non-backward compatible ways), but we already have dedicated OpenTelemetry appenders for several of the most commonly used logging libraries, like log4j or logback. You should be able to use these and expect relatively little breaking changes.
I have 3 question about logging inside srping
First:
spring documentation:
By default, If you use the ‘Starter POMs’, Logback will be used for
logging. Appropriate Logback routing is also included to ensure that
dependent libraries that use Java Util Logging, Commons Logging, Log4J
or SLF4J will all work correctly.
I don't understand that if a third-party library uses a different logger, what problem will be created in the program? If that library uses another logger, that logger is located as a dependency in its jar file, and when the library is added that logger is also added and there is no problem.
second:
I saw in a tutorial that it says that trace and debug are disabled by default in spring because it causes performance problems. I understand why trace is a problem because it must report everything that happens in the program. But why does debug cause performance problems? When I did: debug=true, it didn't take me that much time. So what's the problem?
Third:
In this tutorial, it says that logback does not have a FATAL level. Why not? Is it possible that the spring boot program does not have some of the required settings, but it can still start without the need for FATAL?
Different logging implementations require different configurations. Log4j uses XML and Java-Util-Log (JUL) uses properties. Also the xml sematics differs.
So you do not like to configure all logging implementations individually. You like to configure one logging configuration to rule them all, one source-of-truth for logging-config. This have nothing to do with the main intend of the software you are running. Later logging-frameworks generalize older logging-frameworks, so you need the latest logging-framework to rule them all.
Let me rephrase first: Why do we differ between debug and trace? Debug (or de-bug) is a special condition that let you inspect a bug for debugging purposes. Debug may show clients real-world firstname and family-name, in order to output those informations you need code under debugging-circumstances only. To log them may cause legal problems because you are processing/storing personal informations without permission in log-files. In order to de-bug a software you need the debug-log in 90% of all cases. Only in rare cases you need the trace-log. That meens they differ.
Thats a good one. Fatal for me meens the server has hardware problems (burning hard-drive, loose of power supply). This is indicated by errors. Seriously? I have no idea. I may argue that everything that is fatal-worthit should be an error.
I have been working on a project that logs using what are essentially just println statements with a prefixed string tag. I have been looking into implementing support for an actual logging library such as Logback the past few days and had some questions relating to best-practices about logging in general. I know a lot of what I'm doing is probably stupid, but I want to change :)
When I'm extending the code and adding new features, such as testing a new codec, I have been using liberal logging to ensure the code behaves as expected (instead of actual unit tests), and then using constant booleans at the top to disable that logging when the codec is finished (in case it's needed again or a bug is found, I can flip the boolean while testing). I don't know if the granularity that debug level provides would be enough and would prefer some way to define levels differently for different features. Leaving these enabled by default would really bloat the console and probably effect performance -- is this what filters are usually used for?
I've also found myself in more than one case prepending spaces to my messages so that I can better follow the flow of the code. I've found this to be really helpful. In a way, the tabbed messages are like a debug-debug level.
Doing something
Reading a file
header of file: ...
body of file: ...
Back at main
What are good practices for logging? Can someone refer me a good resource that I can dig into or explain if what I'm doing is stupid and why it's stupid? What are some alternatives? An open source project as an example would be extremely helpful. Thanks, I appreciate any guidance.
Some advice:
Never substitute unit tests for logging only.
Regarding logging you should log whatever makes you find bugs quicker.
Log libraries support async logging which will not affect the performance of your application (log4j2 async logging). Logback supports async too.
Do not use booleans inside your code to decide to log or not to log. Use the logging levels (TRACE, DEBUG, INFO, WARN, ERROR) and set them accordingly. Usually in PROD environment you will use a WARN level and in DEV you can set it on debug.
Logging on different levels depending on the package is quite useful (you can use appenders to customize this and other stuff).
In resume, the important is to read the documentation of whatever library you are using
i am currently working on a java application for some network monitoring tool. In my code i am supposed to use logging a lot. Since its a network management software, the information in logs is quite useful to the user hence its compulsory to use them. But now I am bit confused with what kind of logger method i should prefer. Right now i am using Logger.lop(...//...) since with its help we are also logging the class name and method so its becoming very easy for me (developers) to debug the code and find the error. But finally I am confused should i deliver it to the end user with the same logging mechanism??? Is it any harm to let your user know what kind of class is executing currently , in which method error has occured. I have seen many times in many product in exception handling stacktrace is used so normally we get class name as well. So is there is no problem to let enduser know what your class name and method is??
Before considering the security implications of it, consider the performance. In most logging systems, getting the actual classname and method name dynamically by the logging facility requires reflection and dramatically slows down the logging - usually a synchronous operation. My guess is that in a network monitoring application, you really don't want that.
If you're hard-coding the method name into the log message (either by making it part of the message or by the category), that's a different story. As a security person, I don't consider it to be that big of a deal - if your code is in Java, it can be reversed anyhow, so your code should operate in such a way that it would be secure even if the code was given away.
All that being said, you could either use a different logging configuration for development and production, or those fine-grained messages could go in debug, trace, etc. If you're using log4j, it's generally advisable to use isDebugEnabled to wrap any logging statements which include anything dynamically-calculated as those get calculated before the logging statement determines whether it's enabled.
log4j/logback/slf4j allow you to have different formats for different appenders. For development you can enable a console appender where you include the class name in the format, while for the end-users you can omit it (for a file appender)
It's worth mentioning that such logging is performance costly in Java, contrary to C++ where it is usually implemented with preprocessor. Fortunately, with log4j/logback you can switch it on and off — follow Bozho's advice.
I am refactoring a legacy application where the actual application is scattered in between lot of logging statements. I could immediately benefit by removing TRACE level logging (method entered/exited). However this has proven to be useful many times while debugging an app while integration testing etc. So I am wondering if there is already a working and proven (being used for a while) aspect written for this? I've gone though some online posts but they seem to simple enough (and not sure if they have ever been really used) to be used for real project.
Checkout aspects from "AspectJ in Action" (sources can be downloaded from http://manning.com/laddad2). I have used very close variations of aspects from chapter 10 on real projects.
You can use #Loggable annotation from jcabi-aspects, together with a built-in AspectJ aspect:
#Loggable(Loggable.TRACE)
public String load(URL url) {
return url.openConnection().getContent();
}
It logs through SLF4J, which you can redirect to your own logging facility like, say, log4j.