Otel Span Events To Logs Migration

Span Events to Logs Migration

Use this skill to migrate instrumentation from the Span Event API (AddEvent, RecordException, and language equivalents) to the Logs API, following the accepted OTEP 4430 deprecation plan.

Background

The OpenTelemetry project accepted a plan to deprecate Span.AddEvent and Span.RecordException in favor of emitting events and exceptions through the Logs API. Span Events as a concept remain valid -- they can be emitted via logs that correlate to the active span, and optionally bridged back into the span proto.

Status as of 2026-09-03: OTEP 4430 is accepted, log-based event/exception emission is specified in the Logs API, and the SDK "event to span event bridge" is specified with Development status. The trace API methods AddEvent/RecordException are not yet formally marked Deprecated in the specification -- that step is still pending. Treat existing span-event calls as migration candidates, not automatically invalid code; some SDK-specific equivalents have already changed status (for example OpenTelemetry .NET's Activity.RecordException extension is [Obsolete] in favor of Activity.AddException, which is still a span-event API).

See references/deprecation-plan.md for the full context.

Workflow

0. Prepare before migrating.

• check the project's OpenTelemetry SDK version supports log-based events (check the otel-sdk-versions skill's version index if available)
• identify whether the project has a LoggerProvider configured; if not, one must be set up
• determine if downstream consumers (backends, dashboards, alerts) depend on span events appearing in the span proto envelope

1. Scan the codebase for span event usage.

• search for AddEvent, add_event, addEvent, RecordException, record_exception, recordException, RecordError, record_error, AddException, and language-specific variants
• categorize each call site: general event, exception recording, or informational annotation
• note the span context, attributes, and timestamp usage at each site

2. Classify each call site using the decision tree.

• see references/decision-tree.md for the full classification logic
• the three outcomes are: migrate to log-based event, convert to span attributes, or remove

3. Apply the migration for each call site.

• see references/migration-patterns.md for language-specific before/after patterns
• ensure the replacement log record carries the correct span context, event name, attributes, and timestamp; for exceptions use the applicable semantic-convention event name (normally an operation-specific .exception name), reserving exception for generic handlers
• for exceptions, preserve the applicable semconv attributes: exception.type and exception.message (at least one is required), plus exception.stacktrace when the language/error type makes it meaningful (in Go, omit it unless an error library preserves the origin stack -- do not call runtime.Stack at the emit site)

4. If backward compatibility is needed, configure the SDK bridge.

• see references/backward-compat.md
• this is an SDK-level log processor that converts log-based events back to span events
• only needed when downstream systems require span events in the same proto envelope as the span

5. Verify the migration.

Required Completion Loop

Follow this loop every time:

1. scan and classify all span event call sites
2. migrate each call site following the decision tree and patterns
3. review the changed code against the checklist below
4. re-open the changed files and confirm each checklist item with codebase evidence
5. if any item is unresolved, patch the code or mark it not applicable with a reason, then repeat the review
6. do not finish until every checklist item is completed or explicitly marked not applicable

Do not mark a checklist item complete based on intent alone. Mark it complete only after confirming it in the current codebase.

Migration Checklist

For every item, report one of these statuses in the final answer:

• [x] completed
• [~] not applicable, with a reason
• [ ] unresolved

Include file references as evidence for every completed item.

• [ ] All general span-event call sites identified and classified, including AddEvent / add_event / addEvent and language equivalents such as .NET ActivityEvent.
• [ ] All exception span-event call sites identified and classified, including RecordException / record_exception / recordException and language equivalents such as Go RecordError, Rust record_error, and .NET AddException.
• [ ] A LoggerProvider is configured in the SDK setup (or already existed).
• [ ] Each migrated event uses the Logs API with the correct event name and attributes.
• [ ] Each migrated exception preserves the applicable semconv attributes: exception.type and exception.message (at least one is required), plus exception.stacktrace when the language/error type makes it meaningful.
• [ ] Migrated log records carry the active span context for trace correlation.
• [ ] Call sites classified as "convert to span attributes" now use span attributes instead.
• [ ] Call sites classified as "remove" have been removed with justification.
• [ ] Backward compatibility bridge is configured if downstream systems require span events in the span envelope.
• [ ] No remaining span-event API call sites are left unintentionally; any retained AddEvent / RecordException / RecordError / AddException / ActivityEvent / equivalent call is justified for current-version compatibility.
• [ ] The changed files were re-read after implementation to verify the final state.
• [ ] The final answer includes this checklist, file evidence, and any remaining risks or gaps.

Final Review Format

In the final answer, include the checklist in this format:

• [x] LoggerProvider configured. Evidence: src/telemetry/setup.go:42 -- added OTLP log exporter with batch processor.
• [~] Backward compatibility bridge. Reason: no downstream systems depend on span events in the proto envelope.
• [ ] Exception migration. Missing evidence; re-check required.