fix(bench): bind-mount a writable capture dir for the demo collector (PR-N3.1)

[jensholdgaard]

What

Fixes the first OTel Demo capture dispatch (run 26714187216), which failed at "Bring up the demo".

Root cause

The fileexporter couldn't open its output path:

error: open /tmp/otel-corpus.jsonl: no such file or directory ... id "file/corpus"
Error: cannot start pipelines: failed to start "file/corpus" exporter ...

The demo's collector is a distroless image (v0.142.0) with no writable /tmp, and the fileexporter does not create a missing parent directory — so it failed at startup and the collector crash-looped (restart: unless-stopped), never reaching a running state. My readiness guard correctly failed the step.

The rest of the demo came up fine on the runner — all ~20 images pulled, the collector process started, the OTLP receiver bound 4317/4318. The output path was the only blocker.

Fix

Bind-mount a runner-side directory into the collector at /capture and point the exporter at /capture/logs.jsonl:

• New .github/otel-demo-capture-compose-override.yml adds ${OURIOS_CAPTURE_DIR}:/capture to the otel-collector service.
• Layered onto the demo's base compose via COMPOSE_FILE (colon-separated; base relative to the demo workdir, override absolute so it's project-dir-independent).
• The workflow mkdirs $OURIOS_CAPTURE_DIR (= ${{ github.workspace }}/captured) before up, so the mount target exists and the collector (root) can create the file in it.
• Corpus now lands directly on the runner filesystem → the docker cp extract step is replaced by a non-empty verification + teardown (and dumps collector logs if the capture is empty).
• Exporter path in otel-demo-capture-extras.yml updated /tmp/... → /capture/logs.jsonl, with a comment explaining the distroless-/tmp trap.

Verification

• All three YAML files validate with yaml.safe_load.
• No Rust changes. The capture workflow is workflow_dispatch-only; the real test is the next dispatch after merge (which I'll run + report the corpus shape from).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • Capture workflow now uses a dedicated host directory mounted into the demo environment so the collector writes captured logs directly to the runner filesystem.
  • Collector output path updated to write captured logs to the mounted host location for direct access.
  • Workflow creates and prepares the host directory, verifies captured output in-place (emitting collector logs on failure), then tears down and uploads captured artifacts.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: a42fdabb-85ba-478e-b6f6-d6cd417bdec8

📥 Commits

Reviewing files that changed from the base of the PR and between 45684d1 and 2a1b5aa.

📒 Files selected for processing (1)

• .github/otel-demo-capture-compose-override.yml

🚧 Files skipped from review as they are similar to previous changes (1)

• .github/otel-demo-capture-compose-override.yml

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📝 Walkthrough

Walkthrough

The PR changes the OTel demo corpus capture to mount a host directory into the otel-collector, update the collector exporter to write to /capture/logs.jsonl, and modify the workflow to create the host directory, verify the captured file, and tear down the stack without using docker compose cp.

Changes

Bind-mounted corpus capture flow

Layer / File(s)	Summary
Bind-mount infrastructure setup .github/otel-demo-capture-compose-override.yml, .github/workflows/capture-otel-demo-corpus.yml	New Compose override mounts ${OURIOS_CAPTURE_DIR} on the host into the otel-collector at /capture. Workflow env vars set OURIOS_CAPTURE_DIR and COMPOSE_FILE, and the bring-up step creates and chmods the host directory before docker compose up.
Collector exporter configuration .github/otel-demo-capture-extras.yml	Collector overlay updated: comments removed that assumed in-container /tmp, and the file/corpus exporter now writes to /capture/logs.jsonl (the bind-mounted host path).
Workflow capture directory and verification .github/workflows/capture-otel-demo-corpus.yml	Replaces docker compose cp extraction with a verification step that checks $OURIOS_CAPTURE_DIR/logs.jsonl exists and is non-empty, tails collector logs on failure, and runs docker compose down -v before building the manifest and uploading artifacts.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• jensholdgaard/ourios#73: Related OTel demo corpus capture changes that also adjust exporter path and workflow to use the mounted /capture directory.

Poem

🐰 I dug a tunnel, dug with care,
The logs now hop from there to here,
Mounted paths and checks in place,
No more copying out of space —
Capture lands safe on the host, hooray! 🎩

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main fix: bind-mounting a writable directory for the OTel Demo collector, which directly addresses the root cause of the failed capture run.
Description check	✅ Passed	The description provides comprehensive context (what/why/fix/verification) and explains the root cause, solution, and validation approach, though it does not follow the template structure with its checklist sections.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/otel-demo-capture-writable-path

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[Copilot]

Pull request overview

This PR fixes the workflow-dispatched OTel Demo corpus capture by writing the collector fileexporter output to a bind-mounted host directory instead of an in-container /tmp path, aligning the capture path with the demo collector’s distroless filesystem constraints.

Changes:

• Adds a Compose override that mounts ${OURIOS_CAPTURE_DIR} into the demo collector at /capture.
• Updates the collector fileexporter path to /capture/logs.jsonl.
• Updates the workflow to create the host capture directory, verify the captured file directly, and tear down the demo stack.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
.github/workflows/capture-otel-demo-corpus.yml	Adds shared capture/Compose env, creates the bind-mounted directory, and verifies the host-side corpus file.
.github/otel-demo-capture-extras.yml	Changes the fileexporter destination from /tmp to /capture/logs.jsonl and documents why.
.github/otel-demo-capture-compose-override.yml	Adds the Compose service override that bind-mounts the runner capture directory into the collector.

---

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

.github/workflows/capture-otel-demo-corpus.yml (1)

167-167: ⚡ Quick win

Reuse $OURIOS_CAPTURE_DIR instead of re-deriving the path.

This step hardcodes $GITHUB_WORKSPACE/captured, duplicating the OURIOS_CAPTURE_DIR definition. If the capture dir is ever changed in the env: block, this step silently diverges.

-          cd "$GITHUB_WORKSPACE/captured"
+          cd "$OURIOS_CAPTURE_DIR"

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In @.github/workflows/capture-otel-demo-corpus.yml at line 167, The workflow
step currently changes directory with a hardcoded path cd
"$GITHUB_WORKSPACE/captured" which duplicates the OURIOS_CAPTURE_DIR definition;
update that step to use the environment variable instead (cd
"$OURIOS_CAPTURE_DIR") so the step follows the single source of truth for the
capture directory (look for the step containing the cd command and the env var
OURIOS_CAPTURE_DIR).

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In @.github/otel-demo-capture-compose-override.yml:
- Around line 19-22: The bind-mounted capture directory used by the
otel-collector service (volume entry `${OURIOS_CAPTURE_DIR}:/capture` in the
otel-collector service) must be writable by UID 10001 because the
opentelemetry-collector-contrib image runs as USER 10001:10001; ensure the host
directory referenced by `${OURIOS_CAPTURE_DIR}` is owned by or writable to UID
10001 (e.g., chown -R 10001:10001 ${OURIOS_CAPTURE_DIR} or set permissive mode
like chmod 0777) so the collector's fileexporter can create logs.jsonl without
permission denied errors.

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Nitpick comments:
In @.github/workflows/capture-otel-demo-corpus.yml:
- Line 167: The workflow step currently changes directory with a hardcoded path
cd "$GITHUB_WORKSPACE/captured" which duplicates the OURIOS_CAPTURE_DIR
definition; update that step to use the environment variable instead (cd
"$OURIOS_CAPTURE_DIR") so the step follows the single source of truth for the
capture directory (look for the step containing the cd command and the env var
OURIOS_CAPTURE_DIR).

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 0066e438-e256-4140-8f88-77881881b217

📥 Commits

Reviewing files that changed from the base of the PR and between 02f33ad and 6688c62.

📒 Files selected for processing (3)

• .github/otel-demo-capture-compose-override.yml
• .github/otel-demo-capture-extras.yml
• .github/workflows/capture-otel-demo-corpus.yml

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.