01
Confirm the Service and namespace
Check the actual Service object and its intended namespace. An identically named Service elsewhere can lead to a convincing but irrelevant comparison. Also confirm that the application Pod is Ready before treating an empty backend set as purely a label problem.
The controlled test had a Ready HTTP server with app=selector-api. The Service initially selected app=wrong-label. A request from a separate Pod through the Service name failed even though the application process itself was running.
kubectl -n your-namespace get service your-service -o yaml
kubectl -n your-namespace get pods --show-labels02
Ask the same label question as the controller
Copy the Service selector into a Pod listing. Multiple selector entries are combined, so matching one label is not sufficient if another differs. Compare spelling and values rather than assuming a Deployment name becomes a Pod label automatically.
Do not solve the mismatch by broadening the Service until it catches unrelated workloads. Decide which Pods should receive these requests, then make the smallest consistent change in the intended Service or workload labels.
# Replace this selector with the actual Service selector.
kubectl -n your-namespace get pods -l app=your-app --show-labels
kubectl -n your-namespace get endpointslices \
-l kubernetes.io/service-name=your-service -o yaml03
Separate no matching addresses from not-ready addresses
EndpointSlices show addresses and readiness conditions. A slice can exist with no endpoints, or contain endpoints marked not ready. The latter can indicate a readiness problem even when the selector is correct.
Our wrong selector produced no matching endpoint records. After selecting the intended label, one ready backend appeared. That transition isolated backend selection; it did not require a DNS configuration change or a new Service IP.
04
Repair the intended selector and test traffic
The following is a Service specification fragment rather than a complete manifest. Apply the correct selector through your normal delivery mechanism. Keep its port mapping unchanged during this diagnosis so a separate variable does not obscure the result.
After the controller updated EndpointSlices in our test, the same request through Service DNS returned HTTP 200 with the expected application marker. We checked both the backend record and the actual request.
spec:
selector:
app: your-app05
Continue down the path if endpoints exist but traffic fails
A ready endpoint does not prove that targetPort, application binding, NetworkPolicy, or the Service dataplane is correct. Test those separately once selection is established. A Service that selects the wrong healthy application can also return a misleading success response.
Verify a recognizable application result, not merely any HTTP response. Record the intended labels, the resulting endpoint addresses, and the request outcome so the repair can be reviewed without relying on a screenshot of a green Pod.
Sınırları bil
Reproduced on Kubernetes v1.32.2 with an ordinary selector-based ClusterIP Service and one HTTP Pod. A deliberately wrong app label produced no matching backends. Selectorless Services, external backends, and publishNotReadyAddresses need different interpretation.
Kaynaklar ve ileri okuma
CoreTrailKit tarafından hazırlanan teknik yayın.
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