Secure PHP Development- P126 pdf

An associative array called $ALERTdefines the load average associated with each alert level.. For example, alert condition RED is set to load average 25.. This means that a RED alert is

Listing 16-13 shows a sample configuration file for the load monitoring tool.

Listing 16-13: loadmonitor.conf

<?php define(DEBUG, TRUE);

$ALERT_CONDITIONS = array(‘RED’, ‘YELLOW’, ‘BLUE’);

// When system load has been in any of the following // alert condition for at least last 15 minutes // system is said to be at that alert level // Note: the order does not matter as loadmonitor // automatically chooses the highest alert level

$ALERT[‘RED’] = 25;

$ALERT[‘YELLOW’] = 15;

$ALERT[‘BLUE’] = 5;

$MAIL_TEMPLATE = ‘loadmonitor_mail.txt’;

// Mail every n seconds when alert condition exists // Mail is sent only if the loadmonitor is run // every n-1 seconds Recommend running loadmonitor // every 5 min and mail frequency 30 min (30 * 60 sec) // 0 = always send mail

$MAIL_FREQUENCY = 30 * 60;

// Store when was the last time mail was sent // in a file so that we don’t mail bomb the // admin

$MAIL_CONTROL_FILE = ‘/tmp/loadmonitor.out’;

// Include this program output in mail

$PS_BIN = ‘top’;

$PS_OPT = ‘ -b -n 1’;

?>

Here we have defined $ALERT_CONDITIONSas an array of alerts Currently, there are three alert conditions: RED, YELLOW, BLUE These names are arbitrary and you can choose any name you like.

An associative array called $ALERTdefines the load average associated with each alert level For example, alert condition RED is set to load average 25 This means that a RED alert is sent out when the system is experiencing a load average of 25 for at least the last 15 minutes until the current time.

average of 5 triggers a BLUE alert.

Whenever an alert condition is reached, the $MAIL_TEMPLATEfile is used to send out the alert message However, we do not want to bombard an administrator about

an alert condition that exists among multiple runs of the loadmonitor script For example, if loadmonitor were run every minute, it could note an alert condition and message the administrator every minute This would be bad, so we can use

$MAIL_FREQUENCYto control how frequently an administrator is notified when an alert condition is identified The sample setting is 1800, which is 30 minutes.

Therefore, we only resend notification about an alert condition if the last message was sent at least 30 minutes ago The $MAIL_CONTROL_FILEkeeps the timestamp information for each notification sent This information is used to determine the last delivery time of the alert mail The $PS_BINand $PS_OPT are set to the top command and its argument -b and -n 1 The output of the top command is appended in the mail message to enable an administrator get a glimpse of the trou-bled system just from the e-mail This is very useful if the main administrator receives the alert from a remote location; he or she can guide on-site junior admin-istrators to appropriately deal with the situation based on the information provided

by the top command.

Listing 16-14 shows the loadmonitor script.

Listing 16-14: loadmonitor.php

#!/usr/bin/php -q

<?php require_once(‘loadmonitor.conf’);

require_once(‘class.Linux.inc.php’);

require_once(‘common_functions.php’);

$alertInfo = array();

$system = new sysinfo;

$alertInfo[‘/<%HOST%>/’] = $system->chostname();

$alertInfo[‘/<%IP_ADDR%>/’] = $system->ip_addr();

$alertInfo[‘/<%KERNEL%>/’] = $system->kernel();

$alertInfo[‘/<%TODAY%>/’] = date(‘M-d-Y h:i:s A’);

$loadInfo = $system->loadavg();

$load0 = $loadInfo[0];

$load5 = $loadInfo[1];

$load15 = $loadInfo[2];

$alertInfo[‘/<%LOAD%>/’] = “Now: $load0 “

“Last 5 Min: $load5”

“Last 15 Min: $load15”;

Continued

Listing 16-14(Continued)

$highestAlertRange = 0;

$highestAlert = null;

foreach ($ALERT_CONDITIONS as $alertType) {

$alertRange = $ALERT[$alertType];

if (DEBUG) echo “Alert: $alertRange => “

“Current $load0 $load5 $load15\n”;

if ( ($alertRange <= $load0) &&

($alertRange <= $load5) &&

($alertRange <= $load15) )

{

if (DEBUG) echo “Alert: $alertType ($alertRange)”

“ as load for last 15 min till “

“ now is $load15 $load0 \n”;

if ($alertRange > $highestAlertRange) {

$highestAlertRange = $alertRange;

$highestAlert = $alertType; }

} }

if ($highestAlert != null) {

if (DEBUG) echo “Highest alert $highestAlert \n”;

$alertInfo[‘/<%ALERT%>/’] = $highestAlert;

$ps =execute_program($PS_BIN, $PS_OPT);

$alertInfo[‘/<%PSAUX%>/’] = $ps;

// Find out if last mail sent was // within mail frequency range // or not, if not send mail

if (isOKtoSendMail($MAIL_CONTROL_FILE,

$MAIL_FREQUENCY))

} } exit;

function isOKtoSendMail($ctrlFile = null,

$interval = null) {

$now = time();

if (DEBUG) echo “Now: “ date(‘M-d-Y h:i:s A’, $now) “\n”;

if (file_exists($ctrlFile)) {

// Read file

$lastTime = file($ctrlFile);

if (DEBUG) echo “Last time mail sent: “ date(‘M-d-Y h:i:s A’, $lastTime[0]) “\n”;

} else { // If control file does not exist // Create one and yes we can send mail

if (DEBUG) echo “Create new control file.\n”;

writeControlFile($ctrlFile);

return TRUE;

} // If current time - last time is greater than // or equal to the mail interval, we can send mail

if ($now - $lastTime[0] >= $interval) {

// Update file

if (DEBUG) echo “$now - $lastTime[0] => $interval\n”;

writeControlFile($ctrlFile);

return TRUE;

}

Continued

Listing 16-14(Continued)

// No cannot send mail as we already // did not too long ago

return FALSE;

} function writeControlFile($file = null) {

$now = time();

$fp = fopen($file, ‘w’);

if ($fp) {

if (DEBUG) echo “Writing control $file: $now\n”; fputs($fp, $now);

fclose($fp);

return TRUE;

} else { echo “Error: could not create “

“control file $file \n”;

}

return FALSE;

} function sendAlert($info = null) {

$lines = file($GLOBALS[‘MAIL_TEMPLATE’]);

$contentTypeSet = FALSE;

$message = array();

$headers = array();

foreach ($lines as $str) {

$index++;