Feat/hlc instance id wiring - #352
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Sep 15, 2026
Backends that need per-node identity (e.g. to construct unique hybrid logical clock (HLC) values for stream sequence ids), can receive an identity via StorageConfig during extenddb serve. Default implementations to avoid breaking backends that don't need this.
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What
Make a "instance id" (host+listening port) available to the backend via StorageConfig.
Why
Related to the Cassandra backend mega-PR (#338). Cassandra doesn't support sequences reliably. For stream record sequence numbers in the Cassandra backend, we're using hybrid logical clock (HLC)
values instead. The tie-breaker (which would only be needed under extremely high write loads) is a hash value seeded by instance id assigned at 'serve'. This is unique per node, stable across restarts and valid even when multiple nodes are run on a single host.
Testing done
cargo test --workspace
devtools/run-tests --extenddb --pytest (reviewed and ignoring unrelated CLI test failures)
Checklist
cargo test --workspace)cargo fmt --check)cargo clippy -- -W clippy::pedantic)Storagetrait, auth model, on-diskformat, or public CLI surface, an RFC has been accepted or is linked
below. Otherwise, an ADR captures the decision (link below).
By submitting this pull request, I confirm that my contribution is made under
the terms of the Apache License 2.0 and I agree to the Developer Certificate of
Origin (DCO). See CONTRIBUTING.md for details.