Propagate OTel context into spawned snapshot and move-in tasks

[alco]

Summary

Fixes a bug where telemetry spans defined with OpenTelemetry.with_child_span inside spawned tasks (initial-snapshot and move-in code paths) were silently dropped, hiding expected fine-grained spans such as shape_snapshot.execute_for_shape, shape_snapshot.query_fn, shape_snapshot.checkout_wait, shape_snapshot.setup, and shape_snapshot.query from Honeycomb on hosts whose traffic is dominated by initial snapshots.

Root cause

with_child_span/4 only creates a span when there is already a parent span in the current Erlang process's OTel context. Task.Supervisor.async_nolink / Task.Supervisor.start_child start new processes that do not inherit the caller's OTel context, so in_span_context?() returns false and the whole span subtree is dropped. Three spawn sites were affected:

• Electric.Shapes.Consumer.Snapshotter.start_streaming_snapshot_from_db/4
• Electric.Shapes.PartialModes.query_move_in_async/5
• Electric.Shapes.PartialModes.query_move_in/5

(PartialModes.query_subset/4 is called synchronously from an HTTP-request process that already has a parent span — it was not affected.)

Fix

Capture the context via :otel_ctx.get_current() before each spawn and attach it inside the task closure with :otel_ctx.attach/1 (detached in after). This mirrors the pattern already used for state.otel_ctx in Snapshotter.handle_continue/2.

Test plan

• mix compile clean
• mix test test/electric/shapes/consumer_test.exs — 29 passing
• mix test test/electric/shapes/consumer/move_ins_test.exs test/electric/shapes/consumer/initial_snapshot_test.exs — 60 passing
• After deploy: verify name = shape_snapshot.execute_for_shape AND shape.query_reason = "initial_snapshot" returns rows in Honeycomb (previously 0 across all hosts over 24h)

Refs: https://github.com/electric-sql/alco-agent-tasks/issues/27

🤖 Generated with Claude Code

[claude]

Claude Code Review

Summary

The new commit (b230e901b) addresses the last open suggestion from the previous review by adding a proper @type otel_ctx to the OpenTelemetry module and updating the consumer.ex typespec to use it. The PR is complete and has no remaining issues.

What's Working Well

• Suggestion fully addressed: @type otel_ctx :: {span_ctx() | :undefined, :otel_baggage.t()} is now defined in open_telemetry.ex, span_ctx was promoted from @typep to @type so it can be referenced externally, and the initialize_shape_opts/0 typespec in consumer.ex now reads optional(:otel_ctx) => OpenTelemetry.otel_ctx() | nil — accurate and self-documenting.
• @typedoc added: The new type includes a doc comment explaining its role, which is good practice for a public type that crosses module boundaries.
• No new issues introduced: The commit is a pure typespec improvement; no behavioural changes.

Issues Found

Critical (Must Fix)

None.

Important (Should Fix)

None.

Suggestions (Nice to Have)

None.

Issue Conformance

No linked public issue. The PR description is detailed and provides sufficient context (root cause, affected code paths, fix approach, test plan). The implementation fully matches the described fix.

Previous Review Status

• Suggestion (map() | nil typespec stale in consumer.ex): Resolved in b230e901b. The otel_ctx type is now properly defined and used.

---

Review iteration: 4 | 2026-04-22

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.20%. Comparing base (388ec63) to head (b230e90).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4149   +/-   ##
=======================================
  Coverage   89.20%   89.20%           
=======================================
  Files          25       25           
  Lines        2520     2520           
  Branches      636      638    +2     
=======================================
  Hits         2248     2248           
  Misses        270      270           
  Partials        2        2           

Flag	Coverage Δ
packages/experimental	87.73% <ø> (ø)
packages/react-hooks	86.48% <ø> (ø)
packages/start	82.83% <ø> (ø)
packages/typescript-client	94.30% <ø> (ø)
packages/y-electric	56.05% <ø> (ø)
typescript	89.20% <ø> (ø)
unit-tests	89.20% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.