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Values, can be one of:
- Derive: used for values where a change in the value since it’s last been read is of interest. Can be used to calculate and store a rate.
- Counter: similar to derive values, but take the possibility of a counter wrap around into consideration.
- Gauge: used for values that are stored as is.
- Absolute: used for counters that are reset after reading collectd consist of a value list.
collectd Data Sets
Values lists are often accompanied by data sets that describe the values in more detail. Data sets consist of:
- A type: a name which uniquely identifies a data set.
- One or more data sources (entries in a data set) which include:
- The name of the data source. If there is only a single data source this is set to “value”.
- The type of the data source, one of: counter, gauge, absolute or derive.
- A min and a max value.
Examples of types in collectd
Examples of types in types.db:
bitrate value:GAUGE:0:4294967295
counter value:COUNTER:U:U
if_octets rx:COUNTER:0:4294967295,tx:COUNTER:0:4294967295
In the example above if_octets has two data sources: tx and rx.
collectd notifications
Notifications in collectd are generic messages containing:
- An associated severity, which can be one of OKAY, WARNING, and FAILURE.
- A time.
- A Message
- A host.
- A plugin.
- A plugin instance (optional).
- A type.
- A types instance (optional).
- Meta-data.
Notifications and thresholds
References
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References
•Value length: the number of values in the data set.
•Time: timestamp at which the value was collected.
•Interval: interval at which to expect a new value.
•Host: used to identify the host.
•Plugin: used to identify the plugin.
•Plugin instance (optional): used to group a set of values together. For e.g. values belonging to a DPDK interface.
•Type: unit used to measure a value. In other words used to refer to a data set.
•Type instance (optional): used to distinguish between values that have an identical type.
•meta data: an opaque data structure that enables the passing of additional information about a value list. “Meta data in the global cache can be used to store arbitrary information about an identifier”
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