Yii2.0 日志不存储问题

•  问题

表现形式：在定时任务的常驻进程(死循环)里 yii 配置的log 文件日志无法存储。

在带有终止(exit , die ) 的调试里日志写入正常。

启动循环后（进程常驻）时，无法写入日志。

•  分析

分析源码后得出，日志写入过程是先写入内存，程序终止时用函数

register_shutdown_function 监测到后，调用flush 函数 将日志消息存入指定日志。

•  解决

 手动触发 flush

Yii::$app->log->getLogger()->flush(true);

• 后遗症

若有使用自定义文件存储 app.log 和 自定义路径 都会存储

• 部分源码

 * @since 2.0
 */
class Logger extends Component
{
    /**
     * Error message level. An error message is one that indicates the abnormal termination of the
     * application and may require developer's handling.
     */
    const LEVEL_ERROR = 0x01;
    /**
     * Warning message level. A warning message is one that indicates some abnormal happens but
     * the application is able to continue to run. Developers should pay attention to this message.
     */
    const LEVEL_WARNING = 0x02;
    /**
     * Informational message level. An informational message is one that includes certain information
     * for developers to review.
     */
    const LEVEL_INFO = 0x04;
    /**
     * Tracing message level. An tracing message is one that reveals the code execution flow.
     */
    const LEVEL_TRACE = 0x08;
    /**
     * Profiling message level. This indicates the message is for profiling purpose.
     */
    const LEVEL_PROFILE = 0x40;
    /**
     * Profiling message level. This indicates the message is for profiling purpose. It marks the
     * beginning of a profiling block.
     */
    const LEVEL_PROFILE_BEGIN = 0x50;
    /**
     * Profiling message level. This indicates the message is for profiling purpose. It marks the
     * end of a profiling block.
     */
    const LEVEL_PROFILE_END = 0x60;

    /**
     * @var array logged messages. This property is managed by [[log()]] and [[flush()]].
     * Each log message is of the following structure:
     *
     * ```
     * [
     *   [0] => message (mixed, can be a string or some complex data, such as an exception object)
     *   [1] => level (integer)
     *   [2] => category (string)
     *   [3] => timestamp (float, obtained by microtime(true))
     *   [4] => traces (array, debug backtrace, contains the application code call stacks)
     *   [5] => memory usage in bytes (int, obtained by memory_get_usage()), available since version 2.0.11.
     * ]
     * ```
     */
    public $messages = [];
    /**
     * @var int how many messages should be logged before they are flushed from memory and sent to targets.
     * Defaults to 1000, meaning the [[flush]] method will be invoked once every 1000 messages logged.
     * Set this property to be 0 if you don't want to flush messages until the application terminates.
     * This property mainly affects how much memory will be taken by the logged messages.
     * A smaller value means less memory, but will increase the execution time due to the overhead of [[flush()]].
     */
    public $flushInterval = 1000;
    /**
     * @var int how much call stack information (file name and line number) should be logged for each message.
     * If it is greater than 0, at most that number of call stacks will be logged. Note that only application
     * call stacks are counted.
     */
    public $traceLevel = 0;
    /**
     * @var Dispatcher the message dispatcher
     */
    public $dispatcher;


    /**
     * Initializes the logger by registering [[flush()]] as a shutdown function.
     */
    public function init()
    {
        parent::init();
        register_shutdown_function(function () {
            // make regular flush before other shutdown functions, which allows session data collection and so on
            $this->flush();
            // make sure log entries written by shutdown functions are also flushed
            // ensure "flush()" is called last when there are multiple shutdown functions
            register_shutdown_function([$this, 'flush'], true);
        });
    }

    /**
     * Logs a message with the given type and category.
     * If [[traceLevel]] is greater than 0, additional call stack information about
     * the application code will be logged as well.
     * @param string|array $message the message to be logged. This can be a simple string or a more
     * complex data structure that will be handled by a [[Target|log target]].
     * @param int $level the level of the message. This must be one of the following:
     * `Logger::LEVEL_ERROR`, `Logger::LEVEL_WARNING`, `Logger::LEVEL_INFO`, `Logger::LEVEL_TRACE`,
     * `Logger::LEVEL_PROFILE_BEGIN`, `Logger::LEVEL_PROFILE_END`.
     * @param string $category the category of the message.
     */
    public function log($message, $level, $category = 'application')
    {
        $time = microtime(true);
        $traces = [];
        if ($this->traceLevel > 0) {
            $count = 0;
            $ts = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
            array_pop($ts); // remove the last trace since it would be the entry script, not very useful
            foreach ($ts as $trace) {
                if (isset($trace['file'], $trace['line']) && strpos($trace['file'], YII2_PATH) !== 0) {
                    unset($trace['object'], $trace['args']);
                    $traces[] = $trace;
                    if (++$count >= $this->traceLevel) {
                        break;
                    }
                }
            }
        }
        $this->messages[] = [$message, $level, $category, $time, $traces, memory_get_usage()];
        if ($this->flushInterval > 0 && count($this->messages) >= $this->flushInterval) {
            $this->flush();
        }
    }

    /**
     * Flushes log messages from memory to targets.
     * @param bool $final whether this is a final call during a request.
     */
    public function flush($final = false)
    {
        $messages = $this->messages;
        // https://github.com/yiisoft/yii2/issues/5619
        // new messages could be logged while the existing ones are being handled by targets
        $this->messages = [];
        if ($this->dispatcher instanceof Dispatcher) {
            $this->dispatcher->dispatch($messages, $final);
        }
    }

    .....
    
    其他部分已省略