以编程方式从systemd的日志中读取消息

Question

更新,2013-09-12:

我已经深入挖掘了systemd它journal,而且,我偶然发现了这一点,它说:

systemd-journald将所有收到的日志消息转发到AF_UNIX SOCK_DGRAM套接字/run/systemd/journal/syslog(如果存在),Unix syslog守护程序可以使用它来进一步处理数据.

根据联机帮助页,我确实设置了我的环境以下面还有syslog,我相应地调整了我的代码:

define('NL', "\n\r");

$log = function ()
{
    if (func_num_args() >= 1)
    {
        $message = call_user_func_array('sprintf', func_get_args());

        echo '[' . date('r') . '] ' . $message . NL; 
    }
};

$syslog = '/var/run/systemd/journal/syslog';

$sock = socket_create(AF_UNIX, SOCK_DGRAM, 0);
$connection = socket_connect($sock, $syslog);

if (!$connection)
{
    $log('Couldn\'t connect to ' . $syslog);
}
else
{
    $log('Connected to ' . $syslog);

    $readables = array($sock);

    socket_set_nonblock($sock);

    while (true)
    {
        $read = $readables;
        $write = $readables;
        $except = $readables;

        $select = socket_select($read, $write, $except, 0);

        $log('Changes: %d.', $select);
        $log('-------');
        $log('Read: %d.', count($read));
        $log('Write: %d.', count($write));
        $log('Except: %d.', count($except));

        if ($select > 0)
        {
            if ($read)
            {
                foreach ($read as $readable)
                {
                    $data = socket_read($readable, 4096, PHP_BINARY_READ);

                    if ($data === false)
                    {
                        $log(socket_last_error() . ': ' . socket_strerror(socket_last_error()));
                    }
                    else if (!empty($data))
                    {
                        $log($data);
                    }
                    else
                    {
                        $log('Read empty.');
                    }
                }
            }

            if ($write)
            {
                foreach ($write as $writable)
                {
                    $data = socket_read($writable, 4096, PHP_BINARY_READ);

                    if ($data === false)
                    {
                        $log(socket_last_error() . ': ' . socket_strerror(socket_last_error()));
                    }
                    else if (!empty($data))
                    {
                        $log($data);
                    }
                    else
                    {
                        $log('Write empty.');
                    }
                }
            }
        }
    }
}

这显然只能看到(选择)write套接字上的更改.好吧,可能是这里的东西是错的,所以我试图从他们读,没有运气(也不应该):

[Thu, 12 Sep 2013 14:45:15 +0300] Changes: 1.
[Thu, 12 Sep 2013 14:45:15 +0300] -------
[Thu, 12 Sep 2013 14:45:15 +0300] Read: 0.
[Thu, 12 Sep 2013 14:45:15 +0300] Write: 1.
[Thu, 12 Sep 2013 14:45:15 +0300] Except: 0.
[Thu, 12 Sep 2013 14:45:15 +0300] 11: Resource temporarily unavailable

现在,这让我疯了一点.syslog文档说这应该是可能的.代码有什么问题？

原版的:

我有一个工作原型,简单地说:

while(true)
{
    exec('journalctl -r -n 1 | more', $result, $exit);

    // do stuff
}

但是这感觉不对,并且消耗了太多的系统资源,然后我发现了带有套接字的journald.

我试图连接和阅读:

AF_UNIX, SOCK_DGRAM : /var/run/systemd/journal/socket
AF_UNIX, SOCK_STREAM : /var/run/systemd/journal/stdout

给定的套接字.

随着/var/run/systemd/journal/socket,socket_select看到0变化.随着/var/run/systemd/journal/stdout我总是(每个循环)获得1个更改,0字节数据.

这是我的"读者":

<?php

define('NL', "\n\r");

$journal = '/var/run/systemd/journal/socket';
$jSTDOUT = '/var/run/systemd/journal/stdout';

$journal = $jSTDOUT;

$sock = socket_create(AF_UNIX, SOCK_STREAM, 0);
$connection = @socket_connect($sock, $journal);

$log = function ($message)
{
    echo '[' . date('r') . '] ' . $message . NL; 
};

if (!$connection)
{
    $log('Couldn\'t connect to ' . $journal);
}
else
{
    $log('Connected to ' . $journal);

    $readables = array($sock);

    while (true)
    {
        $read = $readables;

        if (socket_select($read, $write = NULL, $except = NULL, 0) < 1)
        {
            continue;
        }

        foreach ($read as $read_socket)
        {
            $data = @socket_read($read_socket, 1024, PHP_BINARY_READ);

            if ($data === false)
            {
                $log('Couldn\'t read.');

                socket_shutdown($read_socket, 2);
                socket_close($read_socket);

                $log('Server terminated.');
                break 2;
            }

            $data = trim($data);

            if (!empty($data))
            {
                $log($data);
            }
        }
    }

    $log('Exiting.');
}

在读取套接字中没有数据,我认为我做错了什么.

问题,想法:

我的目标是阅读消息,并在其中一些消息上执行回调.

有人能指出我如何以编程方式阅读期刊信息的正确方向吗？

Answer 1

下面的套接字/run/systemd/journal/不适用于此 - …/socket并且…/stdout实际上是只写的(即用于将数据馈送到日志中),而…/syslog套接字不应该由真正的syslogd之外的任何其他东西使用,更不用说journald不​​发送任何元数据.(事实上​​,…/syslog默认情况下套接字甚至不存在 - syslogd实际上必须监听它,并且journald连接到它.)

官方方法是直接从日志文件中读取,并使用inotify监视更改(这是相同的事情journalctl --follow,甚至tail -f /var/log/syslog用于代替轮询).在C程序中,您可以使用libsystemd-journal中的函数,它们将为您进行必要的解析甚至过滤.

在其他语言中,您有三种选择:调用C库; 自己解析日志文件(格式记录); 或者journalctl --follow可以告诉他们输出JSON格式的条目(或更详细的日记导出格式).第三个选项实际上非常有效,因为它只为整个流分配一个进程; 我为它编写了一个PHP包装器(见下文).

最新的systemd版本(v193)也随之而来systemd-journal-gatewayd,它本质上是基于HTTP的版本journalctl; 也就是说,您可以获取JSON或日记 - 导出流http://localhost:19531/entries.(gatewayd和journalctl甚至支持服务器发送的事件,用于从HTML 5网页访问流.)但是,由于明显的安全问题,gatewayd默认是禁用的.

附件:PHP包装器 journalctl --follow

<?php
/* © 2013 Mantas Mikul?nas <grawity@gmail.com>
 * Released under the MIT Expat License <https://opensource.org/licenses/MIT>
 */

/* Iterator extends Traversable {
    void    rewind()
    boolean valid()
    void    next()
    mixed   current()
    scalar  key()
}
calls:  rewind, valid==true, current, key
    next, valid==true, current, key
    next, valid==false
*/

class Journal implements Iterator {
    private $filter;
    private $startpos;
    private $proc;
    private $stdout;
    private $entry;

    static function _join_argv($argv) {
        return implode(" ",
            array_map(function($a) {
                return strlen($a) ? escapeshellarg($a) : "''";
            }, $argv));
    }

    function __construct($filter=[], $cursor=null) {
        $this->filter = $filter;
        $this->startpos = $cursor;
    }

    function _close_journal() {
        if ($this->stdout) {
            fclose($this->stdout);
            $this->stdout = null;
        }
        if ($this->proc) {
            proc_close($this->proc);
            $this->proc = null;
        }
        $this->entry = null;
    }

    function _open_journal($filter=[], $cursor=null) {
        if ($this->proc)
            $this->_close_journal();

        $this->filter = $filter;
        $this->startpos = $cursor;

        $cmd = ["journalctl", "-f", "-o", "json"];
        if ($cursor) {
            $cmd[] = "-c";
            $cmd[] = $cursor;
        }
        $cmd = array_merge($cmd, $filter);
        $cmd = self::_join_argv($cmd);

        $fdspec = [
            0 => ["file", "/dev/null", "r"],
            1 => ["pipe", "w"],
            2 => ["file", "/dev/null", "w"],
        ];

        $this->proc = proc_open($cmd, $fdspec, $fds);
        if (!$this->proc)
            return false;
        $this->stdout = $fds[1];
    }

    function seek($cursor) {
        $this->_open_journal($this->filter, $cursor);
    }

    function rewind() {
        $this->seek($this->startpos);
    }

    function next() {
        $line = fgets($this->stdout);
        if ($line === false)
            $this->entry = false;
        else
            $this->entry = json_decode($line);
    }

    function valid() {
        return ($this->entry !== false);
        /* null is valid, it just means next() hasn't been called yet */
    }

    function current() {
        if (!$this->entry)
            $this->next();
        return $this->entry;
    }

    function key() {
        if (!$this->entry)
            $this->next();
        return $this->entry->__CURSOR;
    }
}

$a = new Journal();

foreach ($a as $cursor => $item) {
    echo "================\n";
    var_dump($cursor);
    //print_r($item);
    if ($item)
        var_dump($item->MESSAGE);
}