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4855-profiles-obi-correlation.md

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Correlating Profiles to OBI Traces

This OTEP introduces a standard communication channel and a specification for correlating profiles to opentelemetry-ebpf-instrumentation (OBI) traces.

Motivation

Currently, OBI traces and profiles operate independently, making it difficult to attribute profiling data to specific traces or spans. By establishing a standard kernel-resident communication channel, this OTEP enables:

  • Correlating profiles with their corresponding traces or spans
  • End-to-end observability workflows without requiring application-level instrumentation

Design Notes

Communication Channel

The communication channel between OBI and the profiler is implemented via an eBPF map pinned at $PINPATH/otel/traces_ctx_v1.

$PINPATH will default to bpffs (/sys/fs/bpf) but there must be options to specify an alternative location. If set, the user-configured

location in OBI must match the one set in the profiler.

On startup, both OBI and the profiler, will create the map and pin it if it doesn't exist.

Data Model

As described in the Profiles Data Model, the shared eBPF map uses a minimal structure to store correlation data. OBI will be responsible of removing entries in order to avoid keeping stale contexts.

eBPF Map Specification

struct {
    __uint(type, BPF_MAP_TYPE_LRU_HASH);
    __type(key, u64);
    __type(value, struct trace_context);
    __uint(max_entries, 1 << 14);
    __uint(pinning, LIBBPF_PIN_BY_NAME);
} traces_ctx_v1 SEC(".maps");
  • Key: (u64)pid_tgid
  • Value:
struct trace_context {
    u8 trace_id[16];
    u8 span_id[8];
};