Record the Delayed Job enqueue as a producer span

[unflxw]

Builds on #1537. This branch is cut from #1535 and cherry-picks that PR's commit, so the collector-mode change can be reviewed against the OpenTelemetry branch here. Once #1537 merges to main and wip-otel-rework is rebased on top of it, the first commit drops out and only the second remains.

Delayed Job is the one background-job backend with no metadata envelope to carry trace context: its payload is a YAML dump of the user's own object, so linking the enqueue to the perform would mean mutating that object and re-serialising it. OpenTelemetry's own Delayed Job instrumentation reaches the same conclusion, so we match it — a PRODUCER span on enqueue and a CONSUMER span on perform, no wire propagation, and the two are not linked. Active Job over Delayed Job still links, through the Active Job __otel_headers layer.

Both commits are tested against Delayed Job's own in-memory test backend (under the new delayed_job gemfile), driving the real enqueue and perform lifecycle in agent and collector mode.

Record the Delayed Job enqueue as a producer span

In collector mode the enqueue.delayed_job event now opens a producer
span, matching the other job backends and OpenTelemetry's own Delayed
Job instrumentation. Delayed Job has no envelope to carry trace context
across the enqueue/perform boundary, so -- like OpenTelemetry -- nothing
is injected and the producer and consumer spans are not linked.

Dual-modes the Delayed Job specs so the collector-mode span shapes are
covered alongside the agent-mode ones.

[backlog-helper]

✔️ All good!

New issue guide | Backlog management | Rules | Feedback

[Copilot]

Pull request overview

Adds Delayed Job enqueue instrumentation to AppSignal, including collector-mode OpenTelemetry semantics by recording the enqueue as a PRODUCER span (without trace-context propagation, matching OTel’s Delayed Job approach). This closes the gap where Delayed Job previously lacked enqueue timeline visibility compared to other job backends.

Changes:

• Add around(:enqueue) instrumentation in DelayedJobPlugin to record enqueue.delayed_job with :opentelemetry_kind => :producer.
• Replace the Delayed Job integration spec with end-to-end coverage using Delayed Job’s in-memory test backend, covering agent + collector modes.
• Add delayed_job gemfiles and CI/build-matrix entries to run the new integration specs.

Reviewed changes

Copilot reviewed 8 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
spec/support/stubs/delayed_job.rb	(Content not provided in prompt) Delayed Job test stubs/support adjustments.
spec/support/helpers/dependency_helper.rb	Add delayed_job_present? to gate specs on bundle contents.
spec/lib/appsignal/integrations/delayed_job_plugin_spec.rb	New end-to-end Delayed Job enqueue/perform specs (agent + collector).
spec/lib/appsignal/hooks/delayed_job_spec.rb	Make hook installation deterministic by installing directly and hiding constants in the “without” case.
lib/appsignal/integrations/delayed_job_plugin.rb	Record enqueue.delayed_job and mark it as a producer span in collector mode.
gemfiles/delayed_job.gemfile	New gemfile to run Delayed Job integration tests.
gemfiles/delayed_job-collector.gemfile	Generated collector overlay gemfile for Delayed Job.
build_matrix.yml	Add delayed_job gemfile variant to the build matrix.
.github/workflows/ci.yml	Generated CI workflow updates to include delayed_job jobs.
.changesets/add-delayed-job-enqueue-instrumentation.md	Changeset documenting the new enqueue instrumentation (minor bump).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[backlog-helper]

• This Pull Request needs more reviews. @lipskis - (More info)

---

This is a message from the daily scheduled checks.

New issue guide | Backlog management | Rules | Feedback