runtime-logging.md

Logging

Note: This section is under development.

Yii provides flexible and extensible logger that is able to handle messages according to severity level or their type. You may filter messages by multiple criteria and forward them to files, email, debugger etc.

Logging basics

Basic logging is as simple as calling one method:

\Yii::info('Hello, I am a test log message');

You can log simple strings as well as more complex data structures such as arrays or objects. When logging data that is not a string the defaulf yii log targets will serialize the value using [[yii\helpers\Vardumper::export()]].

Message category

Additionally to the message itself message category could be specified in order to allow filtering such messages and handing these differently. Message category is passed as a second argument of logging methods and is application by default.

Severity levels

There are multiple severity levels and corresponding methods available:

• [[Yii::trace]] used maily for development purpose to indicate workflow of some code. Note that it only works in development mode when YII_DEBUG is set to true.
• [[Yii::error]] used when there's unrecoverable error.
• [[Yii::warning]] used when an error occurred but execution can be continued.
• [[Yii::info]] used to keep record of important events such as administrator logins.

Log targets

When one of the logging methods is called, message is passed to [[yii\log\Logger]] component accessible as Yii::getLogger(). Logger accumulates messages in memory and then when there are enough messages or when the current request finishes, sends them to different log targets, such as file or email.

You may configure the targets in application configuration, like the following:

[
    'components' => [
        'log' => [
            'targets' => [
                'file' => [
                    'class' => 'yii\log\FileTarget',
                    'levels' => ['trace', 'info'],
                    'categories' => ['yii\*'],
                ],
                'email' => [
                    'class' => 'yii\log\EmailTarget',
                    'levels' => ['error', 'warning'],
                    'message' => [
                        'to' => ['admin@example.com', 'developer@example.com'],
                        'subject' => 'New example.com log message',
                    ],
                ],
            ],
        ],
    ],
]

In the config above we are defining two log targets: [[yii\log\FileTarget|file]] and [[yii\log\EmailTarget|email]]. In both cases we are filtering messages handles by these targets by severity. In case of file target we're additionally filter by category. yii\* means all categories starting with yii\.

Each log target can have a name and can be referenced via the [[yii\log\Logger::targets|targets]] property as follows:

Yii::$app->log->targets['file']->enabled = false;

When the application ends or [[yii\log\Logger::flushInterval|flushInterval]] is reached, Logger will call [[yii\log\Logger::flush()|flush()]] to send logged messages to different log targets, such as file, email, web.

Profiling

Performance profiling is a special type of message logging that can be used to measure the time needed for the specified code blocks to execute and find out what the performance bottleneck is.

To use it we need to identify which code blocks need to be profiled. Then we mark the beginning and the end of each code block by inserting the following methods:

\Yii::beginProfile('myBenchmark');
...code block being profiled...
\Yii::endProfile('myBenchmark');

where myBenchmark uniquely identifies the code block.

Note, code blocks need to be nested properly such as

\Yii::beginProfile('block1');
    // some code to be profiled
    \Yii::beginProfile('block2');
        // some other code to be profiled
    \Yii::endProfile('block2');
\Yii::endProfile('block1');

Profiling results could be displayed in debugger.