Skupper expose - UDP Service

[dot-1q]

Hi!
I was wondering what's the procedure if we want to expose a service/deployment that uses the UDP Protocol.
In the documentation i've only found option for HTTP/S and TCP.

Thanks in advance!

[jiridanek]

Skupper router does not support UDP. You can try to use the --bridge-image option and specify an udp bridge there. I never tried it, so I'd be myself interested in how it goes!

skupper/cmd/skupper/skupper.go

Line 714 in d9aaf1c

cmd.Flags().StringVar(&serviceToCreate.BridgeImage, "bridge-image", "", "The image to use for a bridge running external to the skupper router")

See example at https://github.com/skupperproject/skupper-test-udp-bridge for how it might be used.

skupper expose deployment udp-server --port 8000 --protocol udp --bridge-image=quay.io/skupper/bridge-server

The bridge itself lives at https://github.com/grs/skupper-udp-bridge.

[dot-1q]

Hi @jiridanek, thank you for your help!
Although I followed the example and it did work, with the logs of the udp server showing the messages from the udp client, when I followed the same steps for the my UDP service, sadly there was no connectivity.

Services on VM A:

~$ kubectl get svc -o wide
NAME                   TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)                          AGE   SELECTOR
skupper                NodePort    192.168.87.157           8081:18941/TCP                   44m   app.kubernetes.io/name=skupper-service-controller, ...
skupper-router         NodePort    192.168.87.61            55671:6280/TCP,45671:14063/TCP   44m   app.kubernetes.io/name=skupper-router,app.kubernetes.io/part-of=skupper,...
skupper-router-local   ClusterIP   192.168.87.17            5671/TCP                         44m   app.kubernetes.io/name=skupper-router,app.kubernetes.io/part-of=skupper,...
upf                    ClusterIP   192.168.87.236           8805/UDP                         41m   app=upf,release=upf1
upf-http               ClusterIP   192.168.87.28            8000/TCP,8080/TCP                41m   app=upf,release=upf1

I want to expose upf service, so I did the following:

skupper expose service upf --protocol udp --bridge-image=quay.io/skupper/bridge-server --address upf1

With the new service being created:

~$ kubectl get svc -o wide

NAME                   TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)                          AGE     SELECTOR
skupper                NodePort    192.168.87.157           8081:18941/TCP                   52m     app.kubernetes.io/name=skupper-service-controller,...
skupper-router         NodePort    192.168.87.61            55671:6280/TCP,45671:14063/TCP   52m     app.kubernetes.io/name=skupper-router,...
skupper-router-local   ClusterIP   192.168.87.17            5671/TCP                         52m     app.kubernetes.io/name=skupper-router,app.kubernetes.io/part-of=skupper,...
upf                    ClusterIP   192.168.87.236           8805/UDP                         49m     app=upf,release=upf1
upf-http               ClusterIP   192.168.87.28            8000/TCP,8080/TCP                49m     app=upf,release=upf1
upf1                   ClusterIP   192.168.87.100           8805/UDP                         3m12s   skupper.io/external-bridge=upf1

After this VM B had the following services:

~$ kubectl get svc

NAME                         TYPE        CLUSTER-IP       EXTERNAL-IP     PORT(S)                                       AGE
...
skupper                      NodePort    192.168.85.48              8010:9279/TCP,8080:16592/TCP,8081:20086/TCP   51m
skupper-prometheus           ClusterIP   192.168.85.71              9090/TCP                                      51m
skupper-router               NodePort    192.168.85.200             55671:21087/TCP,45671:20552/TCP               51m
skupper-router-local         ClusterIP   192.168.85.50              5671/TCP                                      51m
smf                          ClusterIP   192.168.85.5               8805/UDP,9089/TCP,29502/TCP                   56m
udm                          ClusterIP   192.168.85.142             29503/TCP                                     56m
udr                          ClusterIP   192.168.85.202             29504/TCP                                     56m
upf1                         ClusterIP   192.168.85.31              8805/UDP                                      84s
webui                        NodePort    192.168.85.168             5000:30002/TCP,9876:32581/TCP                 56m

In my case, the smf is the one who will be connecting with the upf1 service, and checking the logs I can see that the smf pod is sending packets to the correct service address, but nothing arrives in VM A.

On VM A, this is the logs output of the UDP Bridge, which are do not have the same output as the UDP Client-Server example:

~$ kubectl logs skupper-upf1-bridge-848589b8d8-2rg6k

create_udp_listener({ port: 8805, address: 'upf1_8805', multicast: undefined })
Healthz served on port 9090

I don't know how to debug further. Let me know if there's something more I should add!

[grs]

We would expect to see a connect being created on VM A. That is what will direct traffic at the intended target. What does your skupper-services configmap contain?

If you expose the deployment backing the service, instead of the service itself, does that make any difference?

[dot-1q]

Hi @grs , thank you for your reply.
Making the change from exposing service to exposing statefulset solved the UDP bridge issue. Now the pods can communicate via UDP using Skupper.

Thank you both for your help!