Monitoring VMs on OpenStack (or KVM) using Graphite + Collectd
Collect metric of instances via Libvirt on all Compute node
Install Collectd on all Compute node (or KVM node) or any node that installed Libvirt to collect the metrics (ram, cpu, iops,..) of VMs, then push to a Graphite server.

Workflow: Collectd -> Graphite -> Grafana
Install on CentOS 7

```sh
yum install epel-release -y 
yum install collectd -y 
yum install collectd-virt.x86_64 -y
```

Example /etc/collectd.conf file

```sh
Hostname    "compute01"
FQDNLookup   false

LoadPlugin write_graphite
LoadPlugin unixsock
LoadPlugin virt
Interval 120

<Plugin unixsock>
    SocketFile "/var/run/collectd-unixsock"
    SocketGroup "collectd"
    SocketPerms "0770"
    DeleteSocket false
</Plugin>

<Plugin "virt">
   RefreshInterval 120
   Connection "qemu:///system"
   BlockDeviceFormat "target"
   HostnameFormat "uuid"
   InterfaceFormat "address"
   PluginInstanceFormat name
   ExtraStats "cpu_util disk_err domain_state job_stats_background perf vcpupin"
</Plugin>

<Plugin write_graphite>
  <Node "graphite">
    Host "<ip_graphite>"
    Port "2003"
    Protocol "tcp"
    LogSendErrors true
    Prefix "collectd.compute01."
    #Postfix "collectd"
    StoreRates true
    AlwaysAppendDS false
    EscapeCharacter "_"
  </Node>
</Plugin>
```

Start service

```sh
systemctl restart collectd
```

Monitoring VMs on OpenStack or KVM via Libvirt
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