Writing Configuration

This page describes how to write configuration that conforms to Istio’s schemas. All configuration schemas in Istio are defined as protobuf messages. When in doubt, search for the protos.

Translating to YAML

There’s an implicit mapping from protobuf to YAML using protobuf’s mapping to JSON. Below are a few examples showing common mappings you’ll encounter writing configuration in Istio.

Important things to note:

  • YAML fields are implicitly strings
  • Proto repeated fields map to YAML lists; each element in a YAML list is prefixed by a dash (-)
  • Proto messages map to objects; in YAML objects are field names all at the same indentation level
  • YAML is whitespace sensitive and must use spaces; tabs are never allowed

map and message fields

ProtoYAML
message Metric {
        string descriptor_name = 1;
        string value = 2;
        map<string, string> labels = 3;
}

descriptorName: request_count
value: "1"
labels:
  source: origin.ip
  target: target.service

Note that when numeric literals are used as strings (like value above) they must be enclosed in quotes. Quotation marks (") are optional for normal strings.

repeated fields

ProtoYAML
message Metric {
        string descriptor_name = 1;
        string value = 2;
        map<string, string> labels = 3;
}

message MetricsParams {
    repeated Metric metrics = 1;
}

metrics:
- descriptorName: request_count
  value: "1"
  labels:
    source: origin.ip
    target: target.service
- descriptorName: request_latency
  value: response.duration
  labels:
    source: origin.ip
    target: target.service

enum fields

ProtoYAML
enum ValueType {
    STRING = 1;
    INT64 = 2;
    DOUBLE = 3;
    // more values omitted
}

message AttributeDescriptor {
    string name = 1;
    string description = 2;
    ValueType value_type = 3;
}

name: request.duration
value_type: INT64
or
name: request.duration
valueType: INT64

Note that YAML parsing will handle both snake_case and lowerCamelCase field names. lowerCamelCase is the canonical version in YAML.

Nested message fields

ProtoYAML
enum ValueType {
    STRING = 1;
    INT64 = 2;
    DOUBLE = 3;
    // more values omitted
}

message LabelDescriptor {
    string name = 1;
    string description = 2;
    ValueType value_type = 3;
}

message MonitoredResourceDescriptor {
  string name = 1;
  string description = 2;
  repeated LabelDescriptor labels = 3;
}

name: My Monitored Resource
labels:
- name: label one
  valueType: STRING
- name: second label
  valueType: DOUBLE

Timestamp, Duration, and 64 bit integer fields

The protobuf spec special cases the JSON/YAML representations of a few well-known protobuf messages. 64 bit integer types are also special due to the fact that JSON numbers are implicitly doubles, which cannot represent all valid 64 bit integer values.

ProtoYAML
message Quota {
    string descriptor_name = 1;
    map<string, string> labels = 2;
    int64 max_amount = 3;
    google.protobuf.Duration expiration = 4;
}

descriptorName: RequestCount
labels:
  label one: STRING
  second label: DOUBLE
maxAmount: "7"
expiration: 1.000340012s

Specifically, the protobuf spec declares:

ProtoJSON/YAMLExampleNotes
Timestampstring“1972-01-01T10:00:20.021Z”Uses RFC 3339, where generated output will always be Z-normalized and uses 0, 3, 6 or 9 fractional digits.
Durationstring“1.000340012s”, “1s”Generated output always contains 0, 3, 6, or 9 fractional digits, depending on required precision. Accepted are any fractional digits (also none) as long as they fit into nano-seconds precision.
int64, fixed64, uint64string“1”, “-10”JSON value will be a decimal string. Either numbers or strings are accepted.

What’s next

  • TODO: link to overall mixer config concept guide (how the config pieces fit together)