Query parameter-based routing

Emissary can route to target services based on HTTP query parameters with the query_parameters and regex_query_parameters specifications. Multiple mappings with different annotations can be applied to construct more complex routing rules.

The query_parameters annotation

The query_parameters attribute is a dictionary of query_parameter: value pairs. Emissary will only allow requests that match the specified query_parameter: value pairs to reach the target service.

You can also set the value of a query parameter to true to test for the existence of a query parameter.

A basic example

---
apiVersion: getambassador.io/v3alpha1
kind:  Mapping
metadata:
  name:  quote-backend
spec:
  prefix: /backend/
  service: quote
  query_parameters:
    quote-mode: backend
    random-query-parameter: datawire

This will allow requests to /backend/ to succeed only if the quote-mode query parameter has the value backend and the random-query-parameter has the value datawire.

regex_query_parameters

The following mapping will route requests with the quote-mode header that contain values that match the regex.

---
apiVersion: getambassador.io/v3alpha1
kind:  Mapping
metadata:
  name:  quote-backend
spec:
  regex_query_parameters:
    quote-mode: "^[a-z].*"
  prefix: /backend/
  service: quote

A conditional example

---
apiVersion: getambassador.io/v3alpha1
kind:  Mapping
metadata:
  name:  quote-mode
spec:
  prefix: /backend/
  service: quote-mode
  regex_query_parameters:
    quote-mode: .*
---
apiVersion: getambassador.io/v3alpha1
kind:  Mapping
metadata:
  name:  quote-regular
spec:
  prefix: /backend/
  service: quote-regular

This will send requests that contain the quote-mode query parameter (with any value) to the quote-mode target, while routing all other requests to the quote-regular target.