The page describes Istio attributes, what they are and how they are used.
Istio uses attributes to control the runtime behavior of services running in the mesh. Attributes are named and typed pieces of metadata describing ingress and egress traffic and the environment this traffic occurs in. An Istio attribute carries a specific piece of information such as the error code of an API request, the latency of an API request, or the original IP address of a TCP connection. For example:
request.path: xyz/abc
request.size: 234
request.time: 12:34:56.789 04/17/2017
source.ip: 192.168.0.1
destination.service: example
A given Istio deployment has a fixed vocabulary of attributes that it understands. The specific vocabulary is determined by the set of attribute producers being used in the deployment. The primary attribute producer in Istio is Envoy, although specialized Mixer adapters can also generate attributes.
The common baseline set of attributes available in most Istio deployments is defined here.
Istio attributes use Java-like fully qualified identifiers as attribute names. The allowed characters are [_.a-z0-9]. The character "." is used as namespace separator. For example, request.size and source.ip.
Istio attributes are strongly typed. The supported attribute types are defined by ValueType.