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feat: add expvar debug endpoint and build version injection - #33

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emsearcy merged 5 commits into
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arch-350-debug-endpoint
Mar 20, 2026
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feat: add expvar debug endpoint and build version injection#33
emsearcy merged 5 commits into
mainfrom
arch-350-debug-endpoint

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@emsearcy emsearcy commented Mar 20, 2026 •
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Summary

Implements ARCH-350.

Changes

  • /debug/vars expvar endpoint: Registers the Go standard library expvar handler on the HTTP mux at /debug/vars (internal-only; not exposed via ingress HTTPRoute). The blank import of expvar registers its handler on http.DefaultServeMux, which is then mounted at that path.

  • Build version injection: Adds a Version package-level var as an ldflags injection target. Used as the MCP server implementation version string (visible in MCP Inspector) and in --help output.

  • Makefile: Derives version from git describe --tags --dirty --always, giving:

    • v0.4.1 on a tagged commit
    • v0.4.1-3-gabcdef0 between tags
    • v0.4.1-dirty / v0.4.1-3-gabcdef0-dirty with uncommitted changes

  • .ko.yaml: Declares the -X main.Version ldflag using {{.Env.VERSION}} templating, following the same pattern as lfx-v2-member-service.

  • CI workflows: Sets VERSION env var in both ko build steps:

    • Tagged release: VERSION=github.ref_name (e.g. v0.4.1)
    • Main branch: `VERSION=development-

emsearcy added 3 commits March 20, 2026 12:18
@emsearcy
feat: add expvar debug endpoint and build version injection
30bea3c 
Register the expvar debug endpoint on the HTTP mux at /debug/vars
(internal-only; not exposed via ingress HTTPRoute). The blank import of
expvar registers its handler on http.DefaultServeMux, which is then
mounted at that path.

Add a Version package-level var as an ldflags injection target, and use
it as the MCP server implementation version string instead of a
hardcoded literal. The Makefile derives the version from
'git describe --tags --dirty --always', which produces a clean tag on
tagged commits, a tag+offset+hash string between tags, and appends
-dirty when there are uncommitted changes.

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Signed-off-by: Eric Searcy <eric@linuxfoundation.org>
@emsearcy
feat: include version in --help output
de679d6 
Override the FlagSet Usage func to print the version string before the
flag defaults, so 'lfx-mcp-server --help' shows the running version.

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Signed-off-by: Eric Searcy <eric@linuxfoundation.org>
@emsearcy
feat: inject version via ko ldflags in CI builds
aaf135f 
Add .ko.yaml declaring the -X main.Version ldflag using the VERSION
environment variable, following the same pattern as lfx-v2-member-service.

Set VERSION in both ko workflow steps:
- Tagged release: VERSION=github.ref_name (e.g. v0.4.1)
- Main branch: VERSION=development-<sha>

Also name the previously anonymous main-branch build step for clarity.

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Signed-off-by: Eric Searcy <eric@linuxfoundation.org>
@emsearcy
emsearcy requested review from Copilot and jordane and removed request for Copilot March 20, 2026 19:34
@emsearcy
feat: inject version into Dockerfile builds via build arg
5e795a9 
Add a VERSION build arg to the Dockerfile (defaulting to 'dev') and pass
it to the -X main.Version ldflag in the go build command. Update the
docker-build Makefile target to forward VERSION=$(VERSION) so local
Docker builds get the same git-describe version string as make build.
Also change the default DOCKER_TAG from 'latest' to 'local' to avoid
accidentally tagging local builds as latest.

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Signed-off-by: Eric Searcy <eric@linuxfoundation.org>
Copilot AI review requested due to automatic review settings March 20, 2026 19:42
Copilot AI reviewed Mar 20, 2026
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Pull request overview

Adds internal observability and build metadata to the lfx-mcp-server binary by exposing a Go expvar endpoint and injecting a build-time version string used in the MCP implementation metadata and CLI help output.

Changes:

  • Registers /debug/vars (expvar) on the HTTP server mux.
  • Introduces a build-injected main.Version variable and uses it in MCP implementation metadata and --help output.
  • Updates local build (Makefile/Dockerfile) and CI/ko configuration to pass version via ldflags.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file
File Description
Makefile Derives a git-based VERSION, injects it via ldflags, and passes it to Docker builds.
Dockerfile Accepts a VERSION build-arg and injects it via ldflags for local Docker builds.
cmd/lfx-mcp-server/main.go Adds build-time Version, prints it in CLI usage, uses it in MCP implementation metadata, and mounts /debug/vars.
.ko.yaml Configures ko to inject main.Version from VERSION env var at build time.
.github/workflows/ko-build-tag.yaml Sets VERSION from the tag name for tagged ko builds.
.github/workflows/ko-build-main.yaml Sets VERSION to a development SHA-based value for main-branch ko builds.

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Comment thread cmd/lfx-mcp-server/main.go Outdated
Comment thread cmd/lfx-mcp-server/main.go
Comment thread .ko.yaml
@emsearcy
fix: address review comments and lint/vuln failures
f69abd7 
- bump github.com/modelcontextprotocol/go-sdk v1.4.0 -> v1.4.1 to
  resolve GHSA-89xv-2j6f-qhc8 and GHSA-q382-vc8q-7jhj
- add missing package comment to internal/tools/member_write.go
- replace blank expvar import with named import; register
  /debug/vars via expvar.Handler() directly on the local mux instead
  of mounting http.DefaultServeMux
- wrap /debug/vars in localhostOnly middleware so it is reachable via
  kubectl port-forward but blocked from ingress traffic
- add ko-build Makefile target that loads a local image as
  linuxfoundation/lfx-mcp/lfx-mcp-server:local, matching docker-build;
  VERSION is forwarded so the .ko.yaml template resolves correctly

🤖 Generated with [GitHub Copilot](https://github.com/features/copilot) (via Zed)

Signed-off-by: Eric Searcy <eric@linuxfoundation.org>
@emsearcy
emsearcy merged commit 1d601d4 into main Mar 20, 2026
3 checks passed
@emsearcy
emsearcy deleted the arch-350-debug-endpoint branch March 20, 2026 20:25
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@jordane jordane jordane approved these changes

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3 participants

@emsearcy @jordane