CakePHP3 のログで$contextを宜しくロギング

FileLog.php

<?php
/*
 *
 * Copyright 2017 ELASTIC Consultants Inc.
 *
 */

namespace Elastic\ContextLogEngine\Log\Engine;

use Cake\Http\ServerRequest;
use Cake\Log\Engine\FileLog as BaseLogEngine;
use Exception;
use JsonSerializable;

/**
 * FileLog with context
 */
class FileLog extends BaseLogEngine
{

    /**
     * Default config for this class
     *
     * - `levels` string or array, levels the engine is interested in
     * - `scopes` string or array, scopes the engine is interested in
     * - `file` Log file name
     * - `path` The path to save logs on.
     * - `size` Used to implement basic log file rotation. If log file size
     *   reaches specified size the existing file is renamed by appending timestamp
     *   to filename and new log file is created. Can be integer bytes value or
     *   human readable string values like '10MB', '100KB' etc.
     * - `rotate` Log files are rotated specified times before being removed.
     *   If value is 0, old versions are removed rather then rotated.
     * - `mask` A mask is applied when log files are created. Left empty no chmod
     *   is made.
     * - `jsonOptions` json_encode options.
     * - `deepStackTrace` When `exception` is included in the $context, a detailed stack trace is output.
     *
     * @var array
     */
    protected $_defaultConfig = [
        'path' => null,
        'file' => null,
        'types' => null,
        'levels' => [],
        'scopes' => [],
        'rotate' => 10,
        'size' => 10485760, // 10MB
        'mask' => null,
        'jsonOptions' => null,
        'deepStackTrace' => false,
    ];

    /**
     * json_encode options.
     *
     * @var int|null
     */
    protected $_jsonOptions;

    /**
     * When `exception` is included in the $context,
     * a detailed stack trace is output.
     *
     * @var bool
     */
    protected $_deepStackTrace = false;

    /**
     * Sets protected properties based on config provided
     *
     * @param array $config Configuration array
     */
    public function __construct(array $config = [])
    {
        parent::__construct($config);

        if (isset($this->_config['jsonOptions'])) {
            $this->_jsonOptions = $this->_config['jsonOptions'];
        } else {
            $this->_jsonOptions = JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE |
                JSON_PRETTY_PRINT | JSON_PARTIAL_OUTPUT_ON_ERROR;
        }

        if (isset($this->_config['deepStackTrace'])) {
            $this->_deepStackTrace = $this->_config['deepStackTrace'];
        }
    }

    /**
     * {@inheritdoc}
     *
     * @param mixed $data The data to be converted to string and logged.
     * @param array $context Additional logging information for the message.
     * @return string
     */
    protected function _format($data, array $context = [])
    {
        $message = parent::_format($data, $context);

        $dataWithContext = $this->_injectContext($message, $context);

        return parent::_format(json_encode($dataWithContext, $this->_jsonOptions));
    }

    /**
     * merge context data
     *
     * @param string $message
     * @param array $context
     * @return array
     */
    protected function _injectContext($message, array $context)
    {
        $data = compact('message');

        if (isset($context['request']) && $context['request'] instanceof ServerRequest) {
            $data['request'] = [
                'url' => $context['request']->getRequestTarget(),
                'clientIp' => $context['request']->clientIp(),
                'query' => $context['request']->getQuery(),
                'data' => $context['request']->getData(),
            ];
            unset($context['request']);
        }

        if (isset($context['exception']) && $context['exception'] instanceof Exception) {
            $data['exception'] = [
                'message' => $context['exception']->getMessage(),
                'code' => $context['exception']->getCode(),
                'trace' => $this->_deepStackTrace ? $context['exception']->getTrace() : $context['exception']->getTraceAsString(),
            ];
            unset($context['exception']);
        }

        foreach ($context as $key => $value) {
            if ($value instanceof JsonSerializable || is_array($value)) {
                $data[$key] = $value;
            } else {
                $data[$key] = parent::_format($value);
            }
        }

        return $data;
    }
}

プラグインで公開する予定は未定。