In addition to meters, the Telemetry service collects events triggered within an OpenStack environment. This section provides a brief summary of the events format in the Telemetry service.

While a sample represents a single, numeric datapoint within a time-series, an event is a broader concept that represents the state of a resource at a point in time. The state may be described using various data types including non-numeric data such as an instance’s flavor. In general, events represent any action made in the OpenStack system.

Event configuration

By default, ceilometer builds event data from the messages it receives from other OpenStack services.


In releases older than Ocata, it is advisable to set disable_non_metric_meters to True when enabling events in the Telemetry service. The Telemetry service historically represented events as metering data, which may create duplication of data if both events and non-metric meters are enabled.

Event structure

Events captured by the Telemetry service are represented by five key attributes:

A dotted string defining what event occurred such as "compute.instance.resize.start".
A UUID for the event.
A timestamp of when the event occurred in the system.
A flat mapping of key-value pairs which describe the event. The event’s traits contain most of the details of the event. Traits are typed, and can be strings, integers, floats, or datetimes.
Mainly for auditing purpose, the full event message can be stored (unindexed) for future evaluation.

Event indexing

The general philosophy of notifications in OpenStack is to emit any and all data someone might need, and let the consumer filter out what they are not interested in. In order to make processing simpler and more efficient, the notifications are stored and processed within Ceilometer as events. The notification payload, which can be an arbitrarily complex JSON data structure, is converted to a flat set of key-value pairs. This conversion is specified by a config file.


The event format is meant for efficient processing and querying. Storage of complete notifications for auditing purposes can be enabled by configuring store_raw option.

Event conversion

The conversion from notifications to events is driven by a configuration file defined by the definitions_cfg_file in the ceilometer.conf configuration file.

This includes descriptions of how to map fields in the notification body to Traits, and optional plug-ins for doing any programmatic translations (splitting a string, forcing case).

The mapping of notifications to events is defined per event_type, which can be wildcarded. Traits are added to events if the corresponding fields in the notification exist and are non-null.


The default definition file included with the Telemetry service contains a list of known notifications and useful traits. The mappings provided can be modified to include more or less data according to user requirements.

If the definitions file is not present, a warning will be logged, but an empty set of definitions will be assumed. By default, any notifications that do not have a corresponding event definition in the definitions file will be converted to events with a set of minimal traits. This can be changed by setting the option drop_unmatched_notifications in the ceilometer.conf file. If this is set to True, any unmapped notifications will be dropped.

The basic set of traits (all are TEXT type) that will be added to all events if the notification has the relevant data are: service (notification’s publisher), tenant_id, and request_id. These do not have to be specified in the event definition, they are automatically added, but their definitions can be overridden for a given event_type.

Event definitions format

The event definitions file is in YAML format. It consists of a list of event definitions, which are mappings. Order is significant, the list of definitions is scanned in reverse order to find a definition which matches the notification’s event_type. That definition will be used to generate the event. The reverse ordering is done because it is common to want to have a more general wildcarded definition (such as compute.instance.*) with a set of traits common to all of those events, with a few more specific event definitions afterwards that have all of the above traits, plus a few more.

Each event definition is a mapping with two keys:

This is a list (or a string, which will be taken as a 1 element list) of event_types this definition will handle. These can be wildcarded with unix shell glob syntax. An exclusion listing (starting with a !) will exclude any types listed from matching. If only exclusions are listed, the definition will match anything not matching the exclusions.
This is a mapping, the keys are the trait names, and the values are trait definitions.

Each trait definition is a mapping with the following keys:

A path specification for the field(s) in the notification you wish to extract for this trait. Specifications can be written to match multiple possible fields. By default the value will be the first such field. The paths can be specified with a dot syntax ( Square bracket syntax (payload[host]) is also supported. In either case, if the key for the field you are looking for contains special characters, like ., it will need to be quoted (with double or single quotes): payload.image_meta.’org.openstack__1__architecture’. The syntax used for the field specification is a variant of JSONPath
(Optional) The data type for this trait. Valid options are: text, int, float, and datetime. Defaults to text if not specified.
(Optional) Used to execute simple programmatic conversions on the value in a notification field.

Event delivery to external sinks

You can configure the Telemetry service to deliver the events into external sinks. These sinks are configurable in the /etc/ceilometer/event_pipeline.yaml file.

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