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 5 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 +/- ##
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- 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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May 28, 2026
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.
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Leiyks
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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
Leiyks
added a commit
to DataDog/dd-trace-php
that referenced
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Jun 2, 2026
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.
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Jun 17, 2026
Implements the PHP-tracer side of RFC "Signal Service Name Source via Process Tags". Surfaces one of two mutually-exclusive process tags so the backend can distinguish user-set vs tracer-auto-resolved service names: - svc.user:true — DD_SERVICE non-empty (env, INI, OTEL fallback, RC) - svc.auto:<name> — DD_SERVICE empty; tracer auto-resolved the default Per the RFC caveats, no conclusions are drawn from the absence of both. ## Per-span emission (traces) — tracer/serializer.c In ddtrace_serialize_span_to_rust_span's is_first_span block, the auto-resolved default name is read directly from the root span's property_service when its _dd.svc_src is absent (Service Override Source Attribution RFC: cleared svc_src ↔ service is the global default), avoiding a second pass through datadog_default_service_name(). Each span sees its own request's state — no FPM cross-request leak. ## Sidecar (telemetry / remote config / runtime info) — ext/sidecar.c datadog_sidecar_update_process_tags now also calls ddog_sidecar_session_set_default_service_name(transport, …): - Empty CharSlice → sidecar injects svc.user:true - Normalized default → sidecar injects svc.auto:<default> Injection happens at payload emission time in libdatadog (companion PR DataDog/libdatadog#2053), so telemetry / remote-config / runtime-info / stats payloads all see consistent svc.* tagging without baking it into the static process_tags string. ## Tests - New CLI .phpt tests covering svc.user, svc.auto, OTEL fallback as user-defined, and ini_set-driven runtime mutation. - New web-SAPI test ProcessTagsWebTest::testSvcTagDoesNotLeakBetweenRequests proving the per-span design holds across FPM workers. - Existing process_tags.phpt / telemetry_process_tags.phpt updated to expect the appended svc.auto tag.
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.
…tent The `Target` struct in datadog-remote-config derives Hash over all fields including process_tags. Both the sidecar (RC write side) and the tracer (RC read side via ddog_remote_configs_service_env_change) must agree on the Target hash, and the tracer passes the bare process_tags Vec. Augmenting only the sidecar side with svc.* via `process_tags_with_svc_source()` made the Target hashes diverge, orphaning RC configs in SHM (probes never installed, dynamic config never applied). For now revert this single call site to bare process_tags. A proper follow-up should either exclude process_tags from Target's Hash/Eq impl, or separate Target's identity fields from the payload metadata fields. Trace + telemetry svc.* injection is unaffected.
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Implements the PHP-tracer side of RFC "Signal Service Name Source via Process Tags". Surfaces one of two mutually-exclusive process tags so the backend can distinguish user-set vs tracer-auto-resolved service names: - svc.user:true — DD_SERVICE non-empty (env, INI, OTEL fallback, RC) - svc.auto:<name> — DD_SERVICE empty; tracer auto-resolved the default Per the RFC caveats, no conclusions are drawn from the absence of both. In ddtrace_serialize_span_to_rust_span's is_first_span block, the auto-resolved default name is read directly from the root span's property_service when its _dd.svc_src is absent (Service Override Source Attribution RFC: cleared svc_src ↔ service is the global default), avoiding a second pass through datadog_default_service_name(). Each span sees its own request's state — no FPM cross-request leak. datadog_sidecar_update_process_tags now also calls ddog_sidecar_session_set_default_service_name(transport, …): - Empty CharSlice → sidecar injects svc.user:true - Normalized default → sidecar injects svc.auto:<default> Injection happens at payload emission time in libdatadog (companion PR DataDog/libdatadog#2053), so telemetry / remote-config / runtime-info / stats payloads all see consistent svc.* tagging without baking it into the static process_tags string. - New CLI .phpt tests covering svc.user, svc.auto, OTEL fallback as user-defined, and ini_set-driven runtime mutation. - New web-SAPI test ProcessTagsWebTest::testSvcTagDoesNotLeakBetweenRequests proving the per-span design holds across FPM workers. - Existing process_tags.phpt / telemetry_process_tags.phpt updated to expect the appended svc.auto tag.
Leiyks
added a commit
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Jun 17, 2026
Implements the PHP-tracer side of RFC "Signal Service Name Source via Process Tags". Surfaces one of two mutually-exclusive process tags so the backend can distinguish user-set vs tracer-auto-resolved service names: - svc.user:true — DD_SERVICE non-empty (env, INI, OTEL fallback, RC) - svc.auto:<name> — DD_SERVICE empty; tracer auto-resolved the default Per the RFC caveats, no conclusions are drawn from the absence of both. In ddtrace_serialize_span_to_rust_span's is_first_span block, the auto-resolved default name is read directly from the root span's property_service when its _dd.svc_src is absent (Service Override Source Attribution RFC: cleared svc_src ↔ service is the global default), avoiding a second pass through datadog_default_service_name(). Each span sees its own request's state — no FPM cross-request leak. datadog_sidecar_update_process_tags now also calls ddog_sidecar_session_set_default_service_name(transport, …): - Empty CharSlice → sidecar injects svc.user:true - Normalized default → sidecar injects svc.auto:<default> Injection happens at payload emission time in libdatadog (companion PR DataDog/libdatadog#2053), so telemetry / remote-config / runtime-info / stats payloads all see consistent svc.* tagging without baking it into the static process_tags string. - New CLI .phpt tests covering svc.user, svc.auto, OTEL fallback as user-defined, and ini_set-driven runtime mutation. - New web-SAPI test ProcessTagsWebTest::testSvcTagDoesNotLeakBetweenRequests proving the per-span design holds across FPM workers. - Existing process_tags.phpt / telemetry_process_tags.phpt updated to expect the appended svc.auto tag.
…defined flag Addresses review feedback: DD_SERVICE is request-mutable, not session-bound. The previous single FFI conflated the two facts (empty CharSlice meaning "user-defined", non-empty meaning the auto-resolved name), which forced the tracer to re-push state to the sidecar every time DD_SERVICE changed. Split into two independent session fields: - auto_resolved_service_name: Option<String> — process-stable, set once via ddog_sidecar_session_set_default_service_name(name). - user_service_defined: bool — per-request mutable, refreshed via the new ddog_sidecar_session_set_user_service_defined(is_defined) on each RINIT. process_tags_with_svc_source() now emits svc.user:true when user_service_defined is true, else svc.auto:<name> when an auto-resolved name is stored. The old ServiceNameSource enum is dropped.
Leiyks
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Jun 17, 2026
Implements the PHP-tracer side of RFC "Signal Service Name Source via Process Tags". Surfaces one of two mutually-exclusive process tags so the backend can distinguish user-set vs tracer-auto-resolved service names: - svc.user:true — DD_SERVICE non-empty (env, INI, OTEL fallback, RC) - svc.auto:<name> — DD_SERVICE empty; tracer auto-resolved the default Per the RFC caveats, no conclusions are drawn from the absence of both. In ddtrace_serialize_span_to_rust_span's is_first_span block, the auto-resolved default name is read directly from the root span's property_service when its _dd.svc_src is absent (Service Override Source Attribution RFC: cleared svc_src ↔ service is the global default), avoiding a second pass through datadog_default_service_name(). Each span sees its own request's state — no FPM cross-request leak. datadog_sidecar_update_process_tags now also calls ddog_sidecar_session_set_default_service_name(transport, …): - Empty CharSlice → sidecar injects svc.user:true - Normalized default → sidecar injects svc.auto:<default> Injection happens at payload emission time in libdatadog (companion PR DataDog/libdatadog#2053), so telemetry / remote-config / runtime-info / stats payloads all see consistent svc.* tagging without baking it into the static process_tags string. - New CLI .phpt tests covering svc.user, svc.auto, OTEL fallback as user-defined, and ini_set-driven runtime mutation. - New web-SAPI test ProcessTagsWebTest::testSvcTagDoesNotLeakBetweenRequests proving the per-span design holds across FPM workers. - Existing process_tags.phpt / telemetry_process_tags.phpt updated to expect the appended svc.auto tag.
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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.