# Laravel Logging

https://laravel.com/docs/8.x/logging#introduction

> 日誌紀錄是基於 channel，利用 monolog library

# 設定

- 設定檔 `config/logging.php`
- 預設是使用 stack channel，將多個 log channel 變成單一個

## 設定 channel name

'stack' => [
    'driver' => 'stack',
    'name' => 'channel-name',
    'channels' => ['single', 'slack'],
],

可以用的 [drivers](https://laravel.com/docs/8.x/logging#available-channel-drivers)

## Channel Prerequisites

需要一些前置作業

- [single 和 daily](https://laravel.com/docs/8.x/logging#configuring-the-single-and-daily-channels)
- [Papertrail](https://laravel.com/docs/8.x/logging#configuring-the-papertrail-channel)
- [slack](https://laravel.com/docs/8.x/logging#configuring-the-slack-channel)

## Logging Deprecation Warnings

有時候需要通知某些功能在未來會背棄用

'deprecations' => env('LOG_DEPRECATIONS_CHANNEL', 'null'),

# 建立 Log Stacks

'channels' => [
    'stack' => [
        'driver' => 'stack',
        'channels' => ['syslog', 'slack'],
    ],

    'syslog' => [
        'driver' => 'syslog',
        'level' => 'debug',
    ],

    'slack' => [
        'driver' => 'slack',
        'url' => env('LOG_SLACK_WEBHOOK_URL'),
        'username' => 'Laravel Log',
        'emoji' => ':boom:',
        'level' => 'critical',
    ],
],

看 stack 那一部分有兩個 channel，syslog 和 slack 當logging的時候這兩個都有機會去log message

## Log Levels

[RFC 5424](https://datatracker.ietf.org/doc/html/rfc5424) specification 定義的 log level
- emergency
- alert
- critical
- error
- warning
- notice
- info
- debug

所以當我們 log 一個 debug 的訊息 `syslog` channel 會寫入一筆訊息到系統LOG但是部會寫入到 `slack` 因為不是 critical 等級的 LOG

// debug log level
Log::debug('An informational message.');

// emergency log level
Log::emergency('The system is down!');

# Writing Log Messages

use Illuminate\Support\Facades\Log;

Log::emergency($message);
Log::alert($message);
Log::critical($message);
Log::error($message);
Log::warning($message);
Log::notice($message);
Log::info($message);
Log::debug($message);

## Contextual Information

帶參數

use Illuminate\Support\Facades\Log;

Log::info('User failed to login.', ['id' => $user->id]);

需要接下來的 log 都有 request id

Log::withContext([
    'request-id' => $requestId
]);

## Writing To Specific Channels

// 單一
Log::channel('slack')->info('Something happened!');


// 多個
Log::stack(['single', 'slack'])->info('Something happened!');

## On-Demand Channels

不需要先 logging configuration file

use Illuminate\Support\Facades\Log;

Log::build([
  'driver' => 'single',
  'path' => storage_path('logs/custom.log'),
])->info('Something happened!');

You may also wish to include an on-demand channel in an on-demand logging stack.

use Illuminate\Support\Facades\Log;

$channel = Log::build([
  'driver' => 'single',
  'path' => storage_path('logs/custom.log'),
]);

Log::stack(['slack', $channel])->info('Something happened!');

###### tags: `2021` `laravel` `log` `monolog`

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