feat: add Delve remote debugging support by creydr · Pull Request #201 · kubernetes-sigs/mcp-lifecycle-operator

creydr · 2026-05-27T14:41:55Z

Summary

Adds debug-builder and debug stages to the Dockerfile with Delve and debug-compiled binary
Adds config/manager-debug/ kustomize overlay with minimal patches (remove probes, disable leader election, override entrypoint, increase memory)
Adds docker-build-debug and deploy-debug Makefile targets
Documents the debugging workflow in CONTRIBUTING.md

Hint: This came out, while I was debugging through the operator. I thought this might be helpful for others too.

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k8s-ci-robot · 2026-05-27T14:42:03Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: creydr
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k8s-ci-robot · 2026-05-27T14:42:07Z

Hi @creydr. Thanks for your PR.

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Cali0707 · 2026-05-27T14:52:42Z

@creydr these changes look super useful for debugging in cluster, but I'm wondering if maybe it would be simpler to just debug the make run target (runs on your host, connecting to the cluster) rather than changing the in cluster deployment for debugging? That way the dockerfile default entrypoint also doesn't have delve in it

creydr · 2026-05-27T14:58:49Z

@creydr these changes look super useful for debugging in cluster, but I'm wondering if maybe it would be simpler to just debug the make run target (runs on your host, connecting to the cluster) rather than changing the in cluster deployment for debugging? That way the dockerfile default entrypoint also doesn't have delve in it

Ah. I didn't see the make run command. Sure this would be easier in case it behaves like in-cluster. Let me test it that way.

creydr · 2026-05-27T14:59:04Z

/hold

creydr · 2026-05-27T15:23:22Z

Seems we can also debug it locally (I didn't know that it will pick up the correct kubeconfig). And as we don't have any specific volumes or such, this should be enough and we can close this one here.
Thanks @Cali0707 for pointing me to it

creydr · 2026-05-28T10:52:40Z

@Cali0707 I run into some issues with the local debugging. When I create an MCP server (e.g. like in the example), I run into a reconcile loop, because it can't resolve locally the MCP url for the handshake:

{"level":"info","ts":"2026-05-28T12:13:48+02:00","msg":"MCP endpoint handshake failed","controller":"mcpserver","controllerGroup":"mcp.x-k8s.io","controllerKind":"MCPServer","MCPServer":{"name":"test-server","namespace":"default"},"namespace":"default","name":"test-server","reconcileID":"fd73f131-1e8e-46f6-ab9d-020e666b46a3","url":"http://test-server.default.svc.cluster.local:8080/mcp","error":"calling \"initialize\": sending \"initialize\": rejected by transport: Post \"http://test-server.default.svc.cluster.local:8080/mcp\": dial tcp: lookup test-server.default.svc.cluster.local: no such host"}

#208 should address the endless loop on reconciles, but I still have the issue with the handshake. Did you solve this locally (e.g. with something like telepresence)?

Cali0707 · 2026-05-28T18:55:59Z

@creydr I chatted with @matzew this morning and we both realized we hadn't used the local run target since the handshake merged. IMO let's re-open and clean up this PR, and go forwards with the approach you have here

creydr · 2026-05-29T06:14:22Z

@creydr I chatted with @matzew this morning and we both realized we hadn't used the local run target since the handshake merged. IMO let's re-open and clean up this PR, and go forwards with the approach you have here

sure 👍

creydr · 2026-05-29T06:14:53Z

/unhold

creydr · 2026-05-29T06:15:17Z

/cc @Cali0707 @matzew

matzew · 2026-06-01T14:26:57Z

/ok-to-test
/retest

matzew · 2026-06-01T14:27:07Z

@creydr can u rebase?

Adds a debug build target and kustomize overlay to enable remote debugging of the controller running inside a Kubernetes cluster using Delve.

creydr · 2026-06-01T15:07:54Z

@creydr can u rebase?

@matzew rebased

Copilot

Pull request overview

Adds an opt-in “debug build + debug deploy” workflow for running the controller under Delve inside a Kubernetes cluster, making it easier to remote-debug the operator without running it locally.

Changes:

Adds Dockerfile debug-builder / debug stages (Delve + debug-compiled manager) and names the distroless stage production.
Adds config/manager-debug kustomize overlay to deploy a debug-friendly controller manager configuration.
Adds docker-build-debug / deploy-debug Make targets and documents the workflow in CONTRIBUTING.md.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

File	Description
Makefile	Adds `docker-build-debug` and `deploy-debug`; adjusts `docker-build` to target the `production` stage.
Dockerfile	Introduces debug build stages and a Delve-based debug runtime stage.
CONTRIBUTING.md	Documents how to build/deploy and connect an IDE debugger via port-forward.
config/manager-debug/*	Adds a kustomize overlay to disable probes, disable leader election, override entrypoint, and increase memory for debugging.

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creydr · 2026-06-02T10:12:55Z

+# Debug image with Delve
+FROM golang:1.26.3 AS debug
+RUN go install github.com/go-delve/delve/cmd/dlv@latest


Good point. I'll check on the buildx issue

creydr · 2026-06-02T10:13:43Z

+
+# Debug image with Delve
+FROM golang:1.26.3 AS debug
+RUN go install github.com/go-delve/delve/cmd/dlv@latest


As this is only used for development and won't be pushed, we should be fine IMO

creydr · 2026-06-02T10:15:22Z

+      containers:
+      - name: manager
+        command: null


We have some other patches in place too. Regarding potential missing patches: I was able to run the debug image with the current config

Move the production stage after the debug stage so that tools defaulting to the last Dockerfile stage (e.g. docker-buildx) produce the production image. Also add --target production to docker-buildx for explicitness.

creydr · 2026-06-03T12:48:54Z

@aliok can you recheck?

k8s-ci-robot requested a review from ArangoGutierrez May 27, 2026 14:42

k8s-ci-robot requested a review from jaideepr97 May 27, 2026 14:42

k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels May 27, 2026

k8s-ci-robot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label May 27, 2026

k8s-ci-robot added the do-not-merge/hold Indicates that a PR should not merge because someone has issued a /hold command. label May 27, 2026

creydr closed this May 27, 2026

creydr reopened this May 29, 2026

k8s-ci-robot removed the do-not-merge/hold Indicates that a PR should not merge because someone has issued a /hold command. label May 29, 2026

k8s-ci-robot requested review from Cali0707 and matzew May 29, 2026 06:15

creydr force-pushed the feat/delve-debug-support branch from 5b2e03d to 71e56b2 Compare May 29, 2026 10:27

k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Jun 1, 2026

feat: add Delve remote debugging support for in-cluster controller

bbaff53

Adds a debug build target and kustomize overlay to enable remote debugging of the controller running inside a Kubernetes cluster using Delve.

creydr force-pushed the feat/delve-debug-support branch from 71e56b2 to bbaff53 Compare June 1, 2026 14:50

aliok requested a review from Copilot June 2, 2026 10:02

Copilot started reviewing on behalf of aliok June 2, 2026 10:02 View session

Copilot AI reviewed Jun 2, 2026

View reviewed changes

fix: move production stage last in Dockerfile

14aba8e

Move the production stage after the debug stage so that tools defaulting to the last Dockerfile stage (e.g. docker-buildx) produce the production image. Also add --target production to docker-buildx for explicitness.

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creydr commented May 27, 2026

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