feat(sidecar): expose default_service_name for svc.* process tags#2053
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feat(sidecar): expose default_service_name for svc.* process tags#2053Leiyks wants to merge 3 commits into
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Addresses senior review on the prior PR commit. Process tags are per-process (set once, propagated by the sidecar), but the active service name in PHP is request-local (mutable via `ini_set` and OTEL/RC fallbacks). Baking `svc.user`/`svc.auto` into the static process_tags string leaked the latest request's override into subsequent FPM requests. Two cooperating paths now: 1. **Per-span** (`ext/serializer.c::ddtrace_serialize_span_to_rust_span`): computes svc.user/svc.auto from `get_DD_SERVICE()` at serialization time and appends to that span's `_dd.tags.process`. Each span sees exactly its own request's state — no cross-request leak. 2. **Sidecar** (`ext/sidecar.c::ddtrace_sidecar_update_process_tags`): sends the process-level svc source to libdatadog via the new `ddog_sidecar_session_set_default_service_name` FFI. The sidecar injects svc.user/svc.auto into outgoing telemetry/RC/runtime_info payloads at emission time, eliminating the static-string conflict. The libdatadog half is in DataDog/libdatadog#2053; the submodule is bumped here to that commit. Reverts the static svc.* emission and `ddtrace_alter_dd_service` reload hook from 5a55f2d. Tests: - 5 new `.phpt` tests (CLI per-span correctness incl. ini_set + ini_restore) - New PHPUnit `testSvcTagDoesNotLeakBetweenRequests` against the FPM weblog: two sequential requests on the same worker prove svc.* reflects per-request state with no leak. Implements: RFC "Signal Service Name Source via Process Tags" https://docs.google.com/document/d/1c47iSTWxIOHMHfZTF2nT9xfyQaIBP9KJvI9sRn5SvpM
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Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #2053 +/- ##
==========================================
- Coverage 72.92% 72.85% -0.07%
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Files 460 460
Lines 76463 76537 +74
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+ Hits 55758 55760 +2
- Misses 20705 20777 +72
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Leiyks
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Addresses review feedback on PR:
- Wrap `ddog_sidecar_session_set_default_service_name` calls in
`ddtrace_ffi_try` so transport errors surface in the trace log
instead of being silently dropped.
- Use `DDOG_CHARSLICE_C("")` instead of hand-rolled CharSlice struct
literal for the user-defined case (matches the rest of sidecar.c).
- Call `ddtrace_sidecar_update_process_tags()` at the end of
`ddtrace_sidecar_handle_fork` so the child's fresh sidecar session
re-learns the svc.* source after fork; without this, child
telemetry/RC/stats payloads would drop the svc.* tag entirely
until the next external trigger.
Submodule bump picks up the companion stats-payload fix in
DataDog/libdatadog#2053.
Adds `ddog_sidecar_session_set_default_service_name` so tracers can signal whether DD_SERVICE was user-set or auto-resolved (and the resolved name). The sidecar stores this per-session and injects `svc.user:true` or `svc.auto:<default>` into outgoing process-tags payloads (telemetry, remote config, runtime info), per RFC "Signal Service Name Source via Process Tags": https://docs.google.com/document/d/1c47iSTWxIOHMHfZTF2nT9xfyQaIBP9KJvI9sRn5SvpM The companion change in dd-trace-php (PR #3921) wires the new FFI and emits the per-span counterpart on traces directly.
Stats payloads were the one consumer not routed through `process_tags_with_svc_source()` because StatsConfig holds a pre-joined `String`. Two changes: - Build StatsConfig.process_tags from `session.process_tags_with_svc_source()` at construction time so concentrators created after the source is set carry svc.*. - Refresh StatsConfig.process_tags from both `set_session_process_tags` and `set_session_default_service_name` so live updates propagate. Addresses review feedback on initial PR.
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Summary
Adds
ddog_sidecar_session_set_default_service_name(transport, default_service_name)so tracers can communicate whether the application's service name was user-set or tracer-auto-resolved.The sidecar stores this per-session and injects
svc.user:trueorsvc.auto:<default>into outgoing payloads (telemetry, remote config, runtime info) at emission time — eliminating the need for tracers to bake svc.* into their static process_tags string (which would conflict with request-local service mutations in languages like PHP).Implements the sidecar half of the RFC "Signal Service Name Source via Process Tags".
FFI
default_service_name→ServiceNameSource::UserDefined→ sidecar emitssvc.user:truedefault_service_name(pre-normalized viaddog_normalize_process_tag_value) →ServiceNameSource::AutoResolved(name)→ sidecar emitssvc.auto:<name>Internals
ServiceNameSourceenum inservice/mod.rsArc<Mutex<Option<ServiceNameSource>>>field onSessionInfoSessionInfo::process_tags_with_svc_source()helper — single source of truth used by all consumers of session process_tags (telemetry, RC, runtime_info, sidecar_server)set_session_process_tagsCompanion PR
DataDog/dd-trace-php#3921 — PHP tracer wires
ddog_sidecar_session_set_default_service_nameinext/sidecar.cand bumps the submodule to a commit including this change.