Memcached app graphs not populating

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1

Hi, I’m having issues with the memcached app in LibreNMS not drawing any graphs.
It seems identical to the issue mentioned here https://github.com/librenms/librenms/issues/5265

cat /etc/snmp/snmpd.conf

#rocommunity public
#extend redis /etc/snmp/redis.py
extend memcached /etc/snmp/memcached
extend nginx /etc/snmp/nginx
extend mysql /etc/snmp/mysql

syslocation xxx
syscontact  xxx
sysname     librenms

rwuser snmp

cat /etc/snmp/memcached

#!/usr/bin/php
<?php
$m = new Memcached();
$m->addServer('localhost', 11211);
$stats = $m->getStats();

if(is_array($stats))
{
  echo("<<<app-memcached>>>\n");
  echo(serialize($m->getStats()));
  echo("\n");
}
?>

./validate.php

====================================
Component | Version
--------- | -------
LibreNMS  | 1.67-84-g536bb8ac3
DB Schema | 2020_09_22_172321_add_alert_log_index (174)
PHP       | 7.4.10
Python    | 3.6.8
MySQL     | 10.3.17-MariaDB
RRDTool   | 1.7.0
SNMP      | NET-SNMP 5.8
====================================

[OK]    Composer Version: 1.10.13
[OK]    Dependencies up-to-date.
[OK]    Database connection successful
[OK]    Database schema correct

From the command line i can run /etc/snmp/memcached and it will return a bunch of output, which look fine to me. Memcached is also running fine and i can connect to it.
It’s just the app graphs in LibreNMS that are all showing nan.

Seems like the same bug from https://github.com/librenms/librenms/issues/5265 but i’m not so sure where to file a bug report…

The snmp extends for nginx and mysql work fine.
This is a fresh install on CentOS 8, with nginx, mysql, memcached, rrdcached.

Thanks,
JB

2

I ran the command ./poller.php -h HOSTNAME -d -r -f -m applications to look at the output.

I believe the issue is here

SNMP['/usr/bin/snmpget' '-v3' '-l' 'authPriv' '-n' "" '-a' 'SHA' '-A' 'PASSWORD' '-u' 'USER' '-x' 'AES' '-X' 'PASSWORD' '-Oqv' '-M' '/opt/librenms/mibs:/opt/librenms/mibs/supermicro - dell' 'udp:HOSTNAME:161' '.1.3.6.1.4.1.8072.1.3.2.3.1.2.9.109.101.109.99.97.99.104.101.100']
  
Error in packet
Reason: (tooBig) Response message would have been too large.  

Warning: reset() expects parameter 1 to be array, bool given in /opt/librenms/includes/polling/applications/memcached.inc.php on line 14
 memcached()SQL[UPDATE `applications` set `app_state`=?,`app_status`=?,`timestamp`=NOW() WHERE `app_id` = ? ["UNKNOWN","",8] 1.17ms]

Unfortunately i’m not knowledgeable enough with php or python, if anyone would be willing to have a look i’d be eternally grateful :smiley:

JB

3

Hmm, all is working fine on a Centos 7 installation, which has memcached version 1.4.15.
On my Centos 8 installation, which has memcached version 1.5.9 the issue is there…
I’ll try to investigate further

4

Debian Buster, memcached 1.5.6

Same issue. How can we solve this?

5

Did you manage to solve this?
I haven’t…

6

Yes, it required php and and php-memcached. The documentation doesn’t mention that. If one runs a memcached cluster or dedicated memcached node it should not be required to install php. Someone might be able to develop a memcached script that does not require php. For now it works though.

Here the Ansible task:

- name: Memcached Config
  include_tasks: memcached.yml
  when: "( librenms_agent_agentlocal|bool ) and ( 'memcached' in librenms_agent_agentlocal_scripts )"
  tags: ["librenms-agent","snmpd","memcached"]

- name: Install dependencies for memcached script
  become: yes
  package:
    name:
      - php
      - php-memcached
    state: present
  tags: ["librenms-agent","snmpd","memcached"]