Log files are very useful during the system development process to find problems, conflicts, and identify malfunctions.

Magento offers 3 (three) log controls:

1. Navigation monitoring log. View post: Clear Log’s table.

2. System failure log. View post: Error log record number.

3. Log events and exceptions. What we will see in this post.

Why should I

While you are setting up your store, developing modules, customizing pages, installing extensions, it is very important that you monitor the events and exceptions that occur on your system.

It is very common for people to start customizing the entire store, and “out of the blue” something to work as it should, whether it is an address book, a means of payment, or product evaluation.

You may have problems/conflicts in the code that fail to generate a system crash, so you do not have the famous Error log record number. Which does not mean that there are no mistakes.

How to use

As soon as you install Magento, the event and exception log control is turned off. For it is not something essential for the functioning of the system.

But fundamental for those who are developing. So go to:

System > Configuration > Advanced > Developer [Log Settings]

And change the Enabled option to “Yes” and click Save.

Also see that you can customize the name of the files. And below the name it indicates the directory where these files will be managed.

How to read

Now that your system is generating log files, you can track the files to identify possible problems, just go to the indicated directory:

your installation > var > log

Both files will be listed system.log and exception.log.

Where you can use the system.log to generate a debug of the code, with messages of type “method called and returning value X“. Or generate an alert of type “invalid value for calculation on method signature“.

And the exception.log file is where errors are monitored. They are errors similar to those generated by Error log record number, the difference is that they do not even prevent the system from continuing to function. Example:

2013-07-24T07:23:14+00:00 ERR (3): 
exception 'Exception' with message 'Strict Notice: Non-static method Mage_Core_Model_Locale::date() should not be called statically, assuming $this from incompatible context in /Users/mariosam/app/design/frontend/base/default/template/catalog/product/widget/new/content/new_list.phtml on line 74' in /Users/mariosam/app/code/core/Mage/Core/functions.php:245
Stack trace:
#0 /Users/mariosam/app/design/frontend/base/default/template/catalog/product/widget/new/content/new_list.phtml(74): mageCoreErrorHandler(2048, 'Non-static meth...', '/Users/mariosam...', 74, Array)
#1 /Users/mariosam/app/code/core/Mage/Core/Block/Template.php(216): include('/Users/mariosam...')

It continues until the number #20, #30, #40 {main}. But what really matters are the first few lines.

And if you do not know how to interpret the message, copy the information and take to the Bragento forum for help.

Using the log

If you are a developer, you can use the log files to debug your code. Just use the code below:

Exception log:

...
} catch(Exception $e) {
    Mage::logException($e);
}

The signature of the method is this:

public static function logException(Exception $e)

Event Log:

Mage::log('your msg here...');

The signature of the method is this:

public static function log($message, $level = null, $file = '', $forceLog = false)

Note that it is possible to tell the message, an important (level) degree, the name of a (file) to save the log, and if you should force the recording of the same file with log’s system off.

Want other tips on how to use the log file for debugging? See the wiki on the official website: Magento Debugging Tips.

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