docs: RFC for Firecracker snapshots (instant bazel-diff starts)#376
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tinder-maxwellelliott wants to merge 1 commit into
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docs: RFC for Firecracker snapshots (instant bazel-diff starts)#376tinder-maxwellelliott wants to merge 1 commit into
tinder-maxwellelliott wants to merge 1 commit into
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Design doc for capturing a warm Bazel server in a Firecracker microVM snapshot so PR-time bazel-diff runs restore in ~sub-second instead of paying full server warmup + external-repo fetch on every cold start. Scope: CLI hooks (warmup, fingerprint) + a Go orchestration tool, full warm-server snapshots, self-hosted CI. Centers the correctness story (fingerprint cache key + fail-safe fall-back-to-cold) since an incorrect affected set is worse than none. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Summary
Adds a design RFC (
docs/firecracker-snapshots.md) for using Firecracker microVM snapshots to give instant starts of bazel-diff.The win: bazel-diff's own JVM CLI starts in <1s — the cost is the
bazel query deps(//...)it shells out to, which pays full Bazel server warmup + external-repo/bzlmod resolution + Skyframe graph load on every cold start (minutes on a large monorepo). A snapshot captures that warm state once and restores it in ~sub-second, so the PR-time path only re-analyzes changed packages.Decided scope
warmup,fingerprint) + a Go orchestration tool (tools/firecracker/)What the RFC covers
warmup(record entrypoint, clean exit = "safe to snapshot") andfingerprint(cache key); consume reuses existinggenerate-hashes+get-impacted-targetsMODULE.bazel.lock/.bazelrc/ bazel-diff version / flag set, a fail-safe fall-back-to-cold on any mismatch, the fact thatSourceFileHasheralready makes content correctness independent of server incrementality, and a CI canaryThis PR is docs-only
No code changes. Intended as the review artifact before implementation. Phase 1 (the
fingerprint+warmupsubcommands) would follow in a separate PR.🤖 Generated with Claude Code