openstack/openstack-manuals
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openstack-manuals/doc/ha-guide/source/controller-ha-telemetry.rst
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Highly available Telemetry API

The Telemetry service provides a data collection service and an alarming service.

Telemetry central agent

The Telemetry central agent can be configured to partition its polling workload between multiple agents. This enables high availability (HA).

Both the central and the compute agent can run in an HA deployment. This means that multiple instances of these services can run in parallel with workload partitioning among these running instances.

The Tooz library provides the coordination within the groups of service instances. It provides an API above several back ends that can be used for building distributed applications.

Tooz supports various drivers including the following back end solutions:

  • Zookeeper:

    Recommended solution by the Tooz project.

  • Redis:

    Recommended solution by the Tooz project.

  • Memcached:

    Recommended for testing.

You must configure a supported Tooz driver for the HA deployment of the Telemetry services.

For information about the required configuration options to set in the ceilometer.conf, see the coordination section in the OpenStack Configuration Reference.

Note

Only one instance for the central and compute agent service(s) is able to run and function correctly if the backend_url option is not set.

The availability check of the instances is provided by heartbeat messages. When the connection with an instance is lost, the workload will be reassigned within the remaining instances in the next polling cycle.

Note

Memcached uses a timeout value, which should always be set to a value that is higher than the heartbeat value set for Telemetry.

For backward compatibility and supporting existing deployments, the central agent configuration supports using different configuration files. This is for groups of service instances that are running in parallel. For enabling this configuration, set a value for the partitioning_group_prefix option in the polling section in the OpenStack Configuration Reference.

Warning

For each sub-group of the central agent pool with the same partitioning_group_prefix, a disjoint subset of meters must be polled to avoid samples being missing or duplicated. The list of meters to poll can be set in the /etc/ceilometer/pipeline.yaml configuration file. For more information about pipelines see the Data collection and processing section.

To enable the compute agent to run multiple instances simultaneously with workload partitioning, the workload_partitioning option must be set to True under the compute section in the ceilometer.conf configuration file.