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How to Configure Routes using Expressions
Configuring routes using expressions allows for more flexibility and better performance when dealing with complex or large configurations. This how-to guide explains how to switch to the expressions router and how to configure routes with the new expressive domain specific language. Familiar yourself with the Expressions Language Reference before proceeding through the rest of this guide.
Prerequisites
Edit the kong.conf to contain the line router_flavor = expressions
and restart Kong Gateway.
Note: Once you enable expressions, the match fields that traditionally exist on the route object (such as
paths
andmethods
) will no longer be configurable and you must specify Expressions in theexpression
field. A new fieldpriority
will be made available that allows specifying the order of evaluation of configured Expression routes.
Create routes with expressions
To create a new route object using expressions, send a POST
request to the services endpoint:
curl --request POST \
--url http://localhost:8001/services/example-service/routes \
--form-string expression='http.path == "/mock"'
In this example, you associated a new route object with the path /mock
to the existing service example-service
.
The Expressions DSL also allows you to create complex router match conditions:
curl --request POST \
--url http://localhost:8001/services/example-service/routes \
--header 'Content-Type: multipart/form-data' \
--form-string 'expression=(http.path == "/mock" || net.protocol == "https")'
Create complex routes with expressions
You can describe complex route objects using operators within a POST
request:
curl --request POST \
--url http://localhost:8001/services/example-service/routes \
--header 'Content-Type: multipart/form-data' \
--form-string name=complex_object \
--form-string 'expression=(net.protocol == "http" || net.protocol == "https") &&
(http.method == "GET" || http.method == "POST") &&
(http.host == "example.com" || http.host == "example.test") &&
(http.path ^= "/mock" || http.path ^= "/mocking") &&
http.headers.x_another_header == "example_header" && (http.headers.x_my_header == "example" || http.headers.x_my_header == "example2")'
See the expressions language overview page for common use cases and how to write expressions routes for them.
For a list of all available language features, see the expressions language reference.
Matching fields
The following table describes the available matching fields, as well as their associated type when using an expressions based router.
Field | Type | Available in HTTP Subsystem | Available in Stream Subsystem | Description |
---|---|---|---|---|
net.protocol |
String |
✅ | ✅ | Protocol of the route. Roughly equivalent to the protocols field on the Route entity. Note: Configured protocols on the Route entity are always added to the top level of the generated route but additional constraints can be provided by using the net.prococol field directly inside the expression. |
tls.sni |
String |
✅ | ✅ | If the connection is over TLS, the server_name extension from the ClientHello packet. |
http.method |
String |
✅ | ❌ | The method of the incoming HTTP request. (for example, "GET" or "POST" ) |
http.host |
String |
✅ | ❌ | The Host header of the incoming HTTP request. |
http.path |
String |
✅ | ❌ | The normalized request path according to rules defined in RFC 3986. This field value does not contain any query parameters that might exist. |
http.headers.<header_name> |
String[] |
✅ | ❌ | The value(s) of request header <header_name> . Note: The header name is always normalized to the underscore and lowercase form, so Foo-Bar , Foo_Bar , and fOo-BAr all become values of the http.headers.foo_bar field. |
http.queries.<query_parameter_name> |
String[] |
✅ | ❌ | The value(s) of query parameter <query_parameter_name> . |
net.src.ip |
IpAddr |
❌ | ✅ | IP address of the client. |
net.src.port |
Int |
❌ | ✅ | The port number used by the client to connect. |
net.dst.ip |
IpAddr |
❌ | ✅ | Listening IP address where Kong Gateway accepts the incoming connection. |
net.dst.port |
Int |
❌ | ✅ | Listening port number where Kong Gateway accepts the incoming connection. |