perf(world-state): compute genesis values on an ephemeral world state

Author: spalladino

yarn-project/world-state/src/testing.test.ts

@@ -0,0 +1,40 @@
+import { Fr } from '@aztec/foundation/curves/bn254';
+import { MerkleTreeId, PublicDataTreeLeaf } from '@aztec/stdlib/trees';
+import type { GenesisData } from '@aztec/stdlib/world-state';
+
+import { jest } from '@jest/globals';
+
+import { NativeWorldStateService } from './native/index.js';
+
+jest.setTimeout(60_000);
+
+describe('generateGenesisValues world state backend equivalence', () => {
+  // A genesis with both non-empty prefilled public data and a non-zero timestamp, so the
+  // fast-return branch in generateGenesisValues is not taken and the archive root is computed
+  // from an actual world state.
+  const genesis: GenesisData = {
+    prefilledPublicData: [
+      new PublicDataTreeLeaf(new Fr(1000), new Fr(2000)),
+      new PublicDataTreeLeaf(new Fr(3000), new Fr(4000)),
+    ],
+    genesisTimestamp: 1234567890n,
+  };
+
+  const archiveRoot = async (ws: NativeWorldStateService) =>
+    new Fr((await ws.getCommitted().getTreeInfo(MerkleTreeId.ARCHIVE)).root);
+
+  // The consensus-critical guarantee behind computing genesis values on the fsync-off ephemeral
+  // backend instead of tmp: both backends must derive the exact same on-chain genesis archive root.
+  it('ephemeral and tmp produce identical genesis archive roots', async () => {
+    const tmpWs = await NativeWorldStateService.tmp(undefined /* rollupAddress */, true /* cleanupTmpDir */, genesis);
+    const ephemeralWs = await NativeWorldStateService.ephemeral(genesis);
+    try {
+      const tmpRoot = await archiveRoot(tmpWs);
+      const ephemeralRoot = await archiveRoot(ephemeralWs);
+      expect(ephemeralRoot).toEqual(tmpRoot);
+    } finally {
+      await tmpWs.close();
+      await ephemeralWs.close();
+    }
+  });
+});

yarn-project/world-state/src/testing.ts

@@ -14,8 +14,11 @@ async function generateGenesisValues(genesis: GenesisData) {
     };
   }
 
-  // Create a temporary world state to compute the genesis values.
-  const ws = await NativeWorldStateService.tmp(undefined /* rollupAddress */, true /* cleanupTmpDir */, genesis);
+  // Compute the genesis values on a throwaway world state. The archive root derives only from the
+  // prefilled public data and the genesis timestamp, so the fsync-off ephemeral store (no version
+  // manager, no crash-recoverability) produces an identical root while skipping the fsync overhead
+  // that `tmp` pays. close() removes the tmpdir.
+  const ws = await NativeWorldStateService.ephemeral(genesis);
   const genesisArchiveRoot = new Fr((await ws.getCommitted().getTreeInfo(MerkleTreeId.ARCHIVE)).root);
   await ws.close();