reporter: Improve stack hashing for better cachability #2994
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Previously we used the internal hashes of traces from within the opentelemetry-ebpf-profiler, however, that hash is the same whether we end up getting full symbols for eg. interpreted frames, which meant that we couldn't safely cache incomplete stacks. This change introduces a separate hashing mechanism, that hashes the fully symbolized stacks, including whether a frame was symbolized or not, meaning this hash can safely be used to cache those stacks. A relatively unscientific experiment with a test cluster shows roughly a 40-50% reduction in bytes sent over the wire for servers that perform caching. Judging by profiling data (or lack thereof), this change does not appear to have any effect on the baseline CPU usage of the agent.
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Previously we used the internal hashes of traces from within the opentelemetry-ebpf-profiler, however, that hash is the same whether we end up getting full symbols for eg. interpreted frames, which meant that we couldn't safely cache incomplete stacks.
This change introduces a separate hashing mechanism, that hashes the fully symbolized stacks, including whether a frame was symbolized or not, meaning this hash can safely be used to cache those stacks.
A relatively unscientific experiment with a test cluster shows roughly a 40-50% reduction in bytes sent over the wire for servers that perform caching.
Judging by profiling data (or lack thereof), this change does not appear to have any effect on the baseline CPU usage of the agent.