The table of contents in this file indexes third- and fourth-level headings,
so a new subsection that is absent from it is a gap rather than a style
choice.
Compiled out, compiled in and tracing, compiled in with no active span, and
compiled in but disabled by config all have to produce the right wire bytes,
and only two of them are obvious. Tabulate them, and record why the predicate
reads the context directly instead of calling GetSpan(), which allocates a
DefaultSpan in the no-span case.
mutable_ on a protobuf optional submessage allocates it and sets its has-bit
at the call site, before the helper can decide there is nothing to write. A
caller that dereferences it ships an empty TraceContext whenever nothing is
recorded, and its peers each take a branch to extract nothing.
Document the rule with the right and wrong forms side by side.
The conditional-compilation section promised zero overhead when telemetry is
not wanted. The span disappears, but the arguments passed to it do not: the
compiled-out guards are ordinary inline functions, so a to_string() or a hash
in an argument list still runs and its result is then discarded.
State that, show the guard that does remove the work, and name the opposite
case -- the metric macros, which discard their arguments and need no guard.
detached() strips the thread-local OTel Scope so a guard can be safely
moved to and destroyed on another thread; it pops the Scope on the origin
thread and moves the span into a scope-less guard. rootSpan() starts a span
as a fresh trace root (kIsRootSpanKey) so inbound entry points never inherit
an ambient span left active on the thread.
Impl now holds an optional<Scope> (nullopt for detached guards). Updated the
SpanGuard class docs and docs/build/telemetry.md with the cross-thread rules.
The unit test lands on phase2 where the telemetry test module exists.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Flip the tracePeer Setup default and the trace_peer config parser
default from off to on, and update the example config and build doc to
match. Peer spans record only peer_id (a node-local numeric connection
id) plus trust/ledger metadata — no IP addresses or public keys — so
the privacy concern behind disabling it does not apply. The high-volume
characteristic is retained in the docs.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Replace references to non-existent TracingInstrumentation.h with
SpanGuard.cpp pimpl implementation that actually exists on this branch.
Update conditional compilation section to describe the pimpl approach.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add span discard mechanism that drops unwanted spans before they enter
the batch export queue, saving both network bandwidth and storage.
FilteringSpanProcessor is a custom SpanProcessor decorator that wraps
BatchSpanProcessor. SpanGuard::discard() sets a thread-local flag
(tl_discardCurrentSpan) before calling Span::End(). The OTel SDK calls
OnEnd() synchronously on the same thread, where the flag is checked and
cleared to drop the span.
New file: DiscardFlag.h — zero-dependency header for the thread-local
flag, avoiding transitive include bloat from Telemetry.h.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Tempo is now the sole trace backend. Remove Jaeger all-in-one service
from docker-compose, otlp/jaeger exporter from OTel Collector config,
and Jaeger Grafana datasource provisioning file.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
