.. only:: not (epub or latex or html)

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.. _gs_gateway_splitting:

Traffic Splitting Example

HTTP traffic splitting is the process of sending incoming traffic to multiple backend services, based on predefined weights or other criteria. The Cilium Gateway API includes built-in support for traffic splitting, allowing users to easily distribute incoming traffic across multiple backend services. This is very useful for canary testing or A/B scenarios.

This particular example uses the Gateway API to load balance incoming traffic to different backends, starting with the same weights before testing with a 99/1 weight distribution.

.. include:: ../echo-app.rst

Deploy the Cilium Gateway

You can find an example Gateway and HTTPRoute definition in splitting.yaml:

.. literalinclude:: ../../../../examples/kubernetes/gateway/splitting.yaml :language: yaml

Notice the even 50/50 split between the two Services.

Deploy the Gateway and the HTTPRoute:

.. parsed-literal::

$ kubectl apply -f \ |SCM_WEB|\/examples/kubernetes/gateway/splitting.yaml

The preceding example creates a Gateway named cilium-gw that listens on port 80. A single route is defined and includes two different backendRefs (echo-1 and echo-2) and weights associated with them.

.. code-block:: shell-session

$ kubectl get gateway cilium-gw
NAME        CLASS    ADDRESS          PROGRAMMED   AGE
cilium-gw   cilium   172.18.255.200                8s

.. Note::

Some providers like EKS use a fully-qualified domain name rather than an IP address.

Even traffic split

Now that the Gateway is ready, you can make HTTP requests to the services.

.. code-block:: shell-session

$ GATEWAY=$(kubectl get gateway cilium-gw -o jsonpath='{.status.addresses[0].value}')
$ curl --fail -s http://$GATEWAY/echo

Hostname: echo-1-7d88f779b-m6r46

Pod Information:
    node name:      kind-worker2
    pod name:       echo-1-7d88f779b-m6r46
    pod namespace:  default
    pod IP: 10.0.2.15

Server values:
    server_version=nginx: 1.12.2 - lua: 10010

Request Information:
    client_address=10.0.2.252
    method=GET
    real path=/echo
    query=
    request_version=1.1
    request_scheme=http
    request_uri=http://172.18.255.200:8080/echo

Request Headers:
    accept=*/*  
    host=172.18.255.200  
    user-agent=curl/7.81.0  
    x-forwarded-proto=http  
    x-request-id=ee152a07-2be2-4539-b74d-ebcebf912907  

Request Body:
    -no body in request-

Notice that the reply includes the name of the Pod that received the query. For example:

.. code-block:: shell-session

Hostname: echo-2-5bfb6668b4-2rl4t

Repeat the command several times. You should see the reply balanced evenly across both Pods and Nodes. Verify that traffic is evenly split across multiple Pods by running a loop and counting the requests:

.. code-block:: shell-session

while true; do curl -s -k "http://$GATEWAY/echo" >> curlresponses.txt ;done

Stop the loop with Ctrl+C. Verify that the responses are more or less evenly distributed.

.. code-block:: shell-session

$ cat curlresponses.txt| grep -c "Hostname: echo-1"
1221
$ cat curlresponses.txt| grep -c "Hostname: echo-2"
1162

Uneven (99/1) traffic split

Update the HTTPRoute weights, either by using kubectl edit httproute or by updating the value in the original manifest before reapplying it to. For example, set 99 for echo-1 and 1 for echo-2:

.. code-block:: shell-session

backendRefs:
- kind: Service
  name: echo-1
  port: 8080
  weight: 99
- kind: Service
  name: echo-2
  port: 8090
  weight: 1

Verify that traffic is unevenly split across multiple Pods by running a loop and counting the requests:

.. code-block:: shell-session

while true; do curl -s -k "http://$GATEWAY/echo" >> curlresponses991.txt ;done

Stop the loop with Ctrl+C. Verify that responses are more or less evenly distributed.

.. code-block:: shell-session

$ cat curlresponses991.txt| grep -c "Hostname: echo-1"
24739
$ cat curlresponses991.txt| grep -c "Hostname: echo-2"
239