PHP日志代码不稳定，有时只写

Question

I created a logger method on a class, the basic logging code is this:

    // maximum length of file (in characters / bytes)
    $maxlength = 40000;
    $filename = "logs/$this->account_id.log";

    // add to the first line
    $fileContent = file_exists($filename) ? file_get_contents($filename, NULL, NULL, NULL, $maxlength) : "";
    file_put_contents($filename, '['.date('d-m-Y- H:i:s').'] - '.$message.PHP_EOL. $fileContent);

It makes sure the most recent log entries appear first. All works fine, except some messages are logged then reverted back to 3 days ago after a while.

File has write permissions, any ideas what could be going on?

Answer 1

It is highly probable that it is a concurrency issue. You have a separate log file for each user, but a user might send several requests in a short period of time, reaching to the undesired result that several logs are issued in the same time. You need to form some kind of queue either in a database or a standalone service which will receive the messages and will be the only thing responsible to write into the log file.

Example solution:

• you create an RDBMS table user_log(account_id, message, timestamp) whenever a new log is needed. This will actually let the system know that you intend to store some logs
• you create a cron job which will periodically see what users' log files need to be changed and change them