ops: Emit opentelemetry traces via Unix Domain Socket#9078
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I had a test for this too, but |
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Add a new tracing backend that sends completed spans as atomic datagrams over a Unix Domain Socket (AF_UNIX + SOCK_DGRAM), enabled via the CLN_TRACE_SOCKET envvar. Refactor trace.c so span management logic compiles unconditionally rather than being gated behind #if HAVE_USDT. DTRACE_PROBE macros are defined as no-ops when USDT is unavailable. When no backend is active (no USDT, no trace file, no socket), all tracing functions return early via disable_trace. Changelog-Added: tracing: Add a unix-domain socket sink for opentelemetry traces
Add Backend 2 section for the new CLN_TRACE_SOCKET UDS datagram transport. Restructure the existing USDT docs as Backend 1. Add an environment variable reference table and a minimal Python collector example.
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common/trace.chas the ability to emit the traces it collects via a User-Defined Tracepoint which hands off the serialized trace into a ring buffer in the kernel if there is a listener active. This works, but is not available in some environments, specifically Kubernetes tends to not like exposing eBPF endpoints.The challenge in finding a new sink is that it must be capable of supporting concurrent writes from unsynchronized processes (main daemon, subprocesses and plugins), preventing corruption of individual writes. The solution is to use a UDS with datagram mode (UDP) enabled. This means that writes up to the MTU of the medium are guaranteed to be atomic.
The tracing is enabled by setting the
CLN_TRACE_SOCKETenvironment variable, binding a listener to the indicated path and read packets from it. The CLN processes will attach to the socket and use it to deliver its traces.