Monitoring Overview 4.4

This guide provides an overview of the OpenNebula monitoring subsystem. The monitoring subsystem gathers information relative to the hosts and the virtual machines, such as the host status, basic performance indicators, as well as VM status and capacity consumption. This information is collected by executing a set of static probes provided by OpenNebula. The output of these probes is sent to OpenNebula in two different ways: using a push or a pull paradigm. Below you can find a brief description of the two models and when to use one or the other.

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The UDP-push Model

:!: Default. This is the default IM for KVM and Xen in OpenNebula >= 4.4.

In this model, each host periodically sends monitoring data via UDP to the frontend which collects it and processes it in a dedicated module. This distributed monitoring system resembles the architecture of dedicated monitoring systems, using a lightweight communication protocol, and a push model.

This model is highly scalable and its limit (in terms of number of VMs monitored per second) is bounded to the performance of the server running oned and the database server.

Please read the UDP-push guide for more information.

When to Use the UDP-push Model

This mode can be used only with Xen and KVM (VMware only supports the SSH-pull mode).

This monitoring model is adequate when:

  • You are using KVM or Xen (VMware is not supported in this mode)
  • Your infrastructure has a medium-to-high number of hosts (e.g. more than 50)
  • You need a high responsive system
  • You need a high frequently updated monitor information
  • All your hosts communicate through a secure network (UDP packages are not encrypted and their origin is not verified)

The Pull Model

When using this mode OpenNebula periodically actively queries each host and executes the probes via ssh. In KVM and Xen this means establishing an ssh connection to each host and executing several scripts to retrieve this information. Note that VMware uses the VI API for this, instead of a ssh connection.

This mode is limited by the number of active connections that can be made concurrently, as hosts are queried sequentially.

Please read the KVM and Xen SSH-pull guide or the ESX-pull guide for more information.

When to Use the SSH-pull Model

This mode can be used with VMware, Xen and KVM.

This monitoring model is adequate when:

  • Your infrastructure has a low number of hosts (e.g. 50 or less)
  • You are communicating with the hosts through an insecure network
  • You do not need to update the monitoring with a high frequency (e.g. for 50 hosts the monitoring period would be typically of about 5 minutes)

Other Monitorization Systems

OpenNebula can be easily integrated with other monitorization system. Please read the Information Manager Driver integration guide for more information.

The Monitor Metrics

The information manage by the monitoring system includes the typical performance and configuration parameters for the host and VMs, e.g. CPU or network consumption, Hostname or CPU model.

These metrics are gathered by specialized programs, called probes, that can be easily added to the system. Just write your own program, or shell script that returns the metric that you are interested in. Please read the Information Manager Driver integration guide for more information.