Blog
Engineering
Kubernetes
3
minutes

Kubernetes Tips: How to find the Port of a Service with a DNS request

Last week I created a guide for our users to set up an NGINX service as an API Gateway with Qovery. The API gateway must redirect the incoming traffic to the appropriate service with the correct port. My problem is that the API Gateway does not know the ports exposed for every service. In this post, I will show you a quick tip on finding the port of a Kubernetes service with a single DNS request. Let's go!
Romaric Philogène
CEO & Co-founder
Summary
Twitter icon
linkedin icon

The tip

As you probably know, DNS service runs on Kubernetes to resolve the local service names. When your app A needs access to an app B from the same namespace, you will use it as a root domain "app-b.svc". Then your app will look at the nameserver to target (the one running on Kubernetes) and request to resolve "app-b.svc" into an IP address. For your application, it is transparent.

I don't want to make it too long, so here is the DNS request to get the port of a Kubernetes service:

dig +answer srv *._tcp.app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local

You should get an output similar to this one:

; <<>> DiG 9.16.22 <<>> +answer srv *._tcp.app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local
;; global options: +cmd
;; Got answer:
;; WARNING: .local is reserved for Multicast DNS
;; You are currently testing what happens when an mDNS query is leaked to DNS
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 12263
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 2
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 9f7c41b86a20fb70 (echoed)
;; QUESTION SECTION:
;*._tcp.app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local. IN SRV

;; ANSWER SECTION:
*._tcp.app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local. 5 IN SRV 0 100 80 app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local.

;; ADDITIONAL SECTION:
app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local. 5 IN A 172.20.46.46

;; Query time: 4 msec
;; SERVER: 172.20.0.10#53(172.20.0.10)
;; WHEN: Mon Jan 24 12:13:15 UTC 2022
;; MSG SIZE  rcvd: 295

Not clear enough? Here is a request to get only the port

dig +noall +answer srv \*._tcp.app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local | awk '{print $7}'
80

Yes, the port is 80!

How does it work

A DNS service is a database of records. You can see it as a KV store (it is a bit more complex, of course). You can store and return much more than just the IP address. This is what happens here. By asking the DNS service to resolve the SRV record of "*._tcp.app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local" I get the following answer.

;; ANSWER SECTION:
*._tcp.app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local. 5 IN SRV 0 100 80 app-z082e36c4.z489e9616-z209c3fd6.svc.cluster.local.

The SRV record is used as a Service Discovery record. The structure is the following: "IN SRV 0 100 <port> <service>.<ns>.svc.<zone>."

Conclusion

Thanks to Romain Gerard - Software Engineer @ Qovery, for this tip that saves my day 😍

This trick is directly used in my API Gateway run.sh script and is super helpful for our customers. You know how to get the port of one of Kubernetes services right from one of your apps now.

Share on :
Twitter icon
linkedin icon
Tired of fighting your Kubernetes platform?
Qovery provides a unified Kubernetes control plane for cluster provisioning, security, and deployments - giving you an enterprise-grade platform without the DIY overhead.
See it in action

Suggested articles

DevOps
Kubernetes
 minutes
February 2, 2026
Top 10 Platform9 Alternatives: Best managed Kubernetes solutions for scale

Need a better way to manage on-prem Kubernetes? Review 10 alternatives to Platform9, categorized by "Infrastructure Ops" (Rancher) vs. "Developer Experience" (Qovery).

Mélanie Dallé
Senior Marketing Manager
DevOps
Kubernetes
 minutes
February 2, 2026
Top 10 Rafay alternatives for enterprise Kubernetes operations

Is Rafay's complexity slowing you down? Compare the top 10 Rafay alternatives for 2026. From fleet managers like Rancher to developer platforms like Qovery, find the balance between control and velocity.

Mélanie Dallé
Senior Marketing Manager
DevOps
Kubernetes
 minutes
February 2, 2026
Top 10 Spectro Cloud alternatives for multi-cluster fleet management

Don't just manage clusters. Modernize your stack. Compare Spectro Cloud vs. Qovery vs. Rancher to decide between "Fleet Operations" and "Developer Self-Service.

Mélanie Dallé
Senior Marketing Manager
DevOps
Kubernetes
 minutes
February 2, 2026
Top 10 VMware alternatives after the Broadcom acquisition

Hit by Broadcom's VMware price hikes? Compare the top 10 alternatives for 2026, from direct replacements like Proxmox and Nutanix to modernization platforms like Qovery.

Mélanie Dallé
Senior Marketing Manager
DevOps
Kubernetes
Platform Engineering
6
 minutes
February 2, 2026
10 Red Hat OpenShift alternatives to reduce licensing costs

Is OpenShift too expensive? Discover the best alternatives for 2026. Whether you need Developer Self-Service (Qovery) or Hybrid Cluster Ops (Rancher), find the right fit for your team.

Morgan Perry
Co-founder
Kubernetes
 minutes
January 29, 2026
Kubernetes management: Best practices for enterprise scaling and cost optimization

Master enterprise Kubernetes management in 2026. Learn best practices for security, FinOps, and reliability, and see how AI-agentic platforms simplify operations.

Mélanie Dallé
Senior Marketing Manager
Kubernetes
Platform Engineering
Infrastructure Management
 minutes
January 28, 2026
The top 3 OpenShift pains in 2026 (and how platform teams respond)

Is OpenShift becoming too expensive or complex for your team? Discover the top 3 OpenShift pain points; from the "pricing inversion" to vendor lock-in and see why agile platform teams are migrating to modular, developer-first alternatives like Qovery.

Mélanie Dallé
Senior Marketing Manager
AI
Qovery
3
 minutes
January 28, 2026
How Qovery uses Qovery to speed up its AI project

Discover how Qovery leverages its own platform to accelerate AI development. Learn how an AI specialist deployed a complex stack; including LLMs, QDrant, and KEDA - in just one day without needing deep DevOps or Kubernetes expertise. See how the "dogfooding" approach fuels innovation for our DevOps Copilot.

Romain Gérard
Staff Software Engineer

It’s time to change
the way you manage K8s

Turn Kubernetes into your strategic advantage with Qovery, automating the heavy lifting while you stay in control.

Talk to an expertGet Qovery free