SNMP Results inaccurate ?

[linickx]

Hi,

I want to write my cpu usage into a database (which will eventually be graphed), I've read that you have to add up ssCpuRawUser.0, ssCpuRawSystem.0, ssCpuRawNice.0 to get total cpu usage.

I've started my poller...

[code]
<?php

# Note to me !
# Command Line snmpget -v 2c -c NOT-public localhost ssCpuRawSystem.0

// ez_sql setup.
require_once "config.php";

// SNMP Setup
$TARGET = "localhost";
$CSTRING = "public";
$OIDs = array( 1 => 'ssCpuRawUser.0', 'ssCpuRawSystem.0', 'ssCpuRawNice.0');

// The Loop
foreach($OIDs as $CURRENT_IOD) {
        // Do SNMP Stuff
        $VAL1 = snmpget($TARGET, $CSTRING, $CURRENT_IOD);
        sleep(2);
        $VAL2 = snmpget($TARGET, $CSTRING, $CURRENT_IOD);
        // Fix Values to do Maths...
        $stringlength = strlen($VAL1);
        $VAL1 = substr($VAL1, 11, $stringlength);
        $stringlength = strlen($VAL1);
        $VAL2 = substr($VAL2, 11, $stringlength);
        $DELTA = ( $VAL1 - $VAL2 );
        if ( $DELTA < 1 ) {
                $DELTA = $DELTA * -1;
        }
        $ANSWER = ( $DELTA / 200 ) * 100;

        // debuggered
        // echo "$CURRENT_IOD : $VAL1 : $VAL2 = $ANSWER% <br />";

        $NOW = time();
        // Save Results
        $db->query("INSERT INTO snmp_results (id, oid, date, result) VALUES (NULL, \"$CURRENT_IOD\", $NOW, $ANSWER)");
        // more debuggered
        #$db->debug();
}

?>
[/code]

But one of the ssCpuRawUser.0 has come back as 200% !!!!! can anyone spot what I'm doing wrong ?

[Destruction]

Could it be this part...
$stringlength = strlen($VAL1);
$VAL2 = substr($VAL2, 11, $stringlength);

If not, at least that's one thing that'd need changing perhaps.  Although realistically it sounds like it's the math that's at fault.  Also dividing by 200 then multiplying by 100 is the same as dividing by 2, so I'm wondering why the extra work?  Also, why multipy by negative 1?

Dest

[redbullmarky]

more of a maths question, but it'll depend what the MAX total could be. you'd need something like
(ACTUAL TOTAL / MAX POSSIBLE TOTAL) * 100
which you'd need to check.

[linickx]

[quote author=Destruction link=topic=123245.msg509118#msg509118 date=1169293045]
Could it be this part...
$stringlength = strlen($VAL1);
$VAL2 = substr($VAL2, 11, $stringlength);
[/quote]

This bit was to fix, the output, which by default is "Counter32: 123456", and I just wanted to grab "123456"

[quote author=Destruction link=topic=123245.msg509118#msg509118 date=1169293045]
If not, at least that's one thing that'd need changing perhaps.  Although realistically it sounds like it's the math that's at fault.  Also dividing by 200 then multiplying by 100 is the same as dividing by 2, so I'm wondering why the extra work?  Also, why multiply by negative 1?
[/quote]

You're right, the maths is rubbish ([i]& my maths[/i]), I was trying to get it readable... I've lost the reference I read, but CPU percentage, was something like, take 2 snmp_get readings, take the delta* of the two counter readings, and divide that number by the time (in ticks**) between the two readings... then finally multiply by 100 to get a percentage.

*delta, I reckon, this is a positive number between numbers, i.e. the difference between 3 & 5 is -2, where as the delta is 2... hence multiply by -1 ([i]I might be wrong[/i]).

**ticks, I think a tick is 0.01 seconds ([i]again could be wrong again[/i]).

I wonder if anyone here has tried to do anything similar ?

[Destruction]

Just to clarify:  I was pointing out that you have strlen val1 instead of val2, wondering if it made any difference.

[linickx]

[quote author=Destruction link=topic=123245.msg509352#msg509352 date=1169343275]
Just to clarify:  I was pointing out that you have strlen val1 instead of val2, wondering if it made any difference.
[/quote]

DOH !! :-[