atenet: make xDS snapshot versions restart-unique - #699
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NekoPunch (orangeCatDeveloper) wants to merge 1 commit into
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atenet: make xDS snapshot versions restart-unique#699NekoPunch (orangeCatDeveloper) wants to merge 1 commit into
NekoPunch (orangeCatDeveloper) wants to merge 1 commit into
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The in-memory version counter restarted at 1 on every router boot; if Envoy reconnected still holding an identical version string the snapshot cache saw a match and skipped the push, stranding Envoy on pre-restart config. Versions now carry a per-process epoch (unix seconds plus a random suffix) so no incarnation repeats an earlier one's strings, even across clock jumps. Fixes agent-substrate#617.
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Fixes #617
Summary
The xDS snapshot version was an in-memory counter starting at 0, so every router restart re-minted "1", "2", … go-control-plane's snapshot cache compares version strings for equality and skips the push when Envoy already reports that version, so a restarted router whose counter lands on the string Envoy still holds leaves Envoy silently stranded on pre-restart config.
Versions are now
<unix-seconds>-<8-char random>-<counter>— a per-process epoch no incarnation can repeat, even if the clock jumps backwards across a restart. version_info is opaque to Envoy and only ever compared for equality, so the format change is safe.Test plan
TestSnapshotVersionsUniqueAcrossRestarts: two XdsServer instances (simulating a restart) each deploy snapshots through the real SnapshotCache; asserts no version string repeats within or across instances.Live verification on a kind cluster: deployed the router, confirmed Envoy ACKed the new format via
config_dump, then SIGKILLed only the router container (Envoy kept running holding the old version) — after the restart Envoy ACKed a new-epoch version, proving the re-push reaches a reconnecting Envoy.Tests pass
Appropriate changes to documentation are included in the PR (none needed)