Rollup state machine failure recovery (#481)

* Adding recoverability to RollupStateMachine

Other:
* updating SparseMerkleTreeImpl to the async static factory approach and updating the many many references
* Making Aggregator constructor private in favor of async static factory method
* Adding some logging in merkle tree and state machine init functions

packages/contracts/test/helpers/RollupBlock.ts

@@ -52,7 +52,7 @@ export class RollupBlock {
   public async generateTree(): Promise<void> {
     // Create a tree!
     const treeHeight = Math.ceil(Math.log2(this.transitions.length)) + 1 // The height should actually not be plus 1
-    this.tree = new SparseMerkleTreeImpl(
+    this.tree = await SparseMerkleTreeImpl.create(
       new BaseDB(new MemDown('') as any, 256),
       undefined,
       treeHeight

packages/contracts/test/merklization/RollupMerkleUtils.spec.ts

@@ -17,6 +17,7 @@ import {
   BigNumber,
   BaseDB,
   SparseMerkleTreeImpl,
+  newInMemoryDB,
 } from '@pigi/core'
 import MemDown from 'memdown'
 
@@ -32,19 +33,15 @@ async function createSMTfromDataBlocks(
 ): Promise<SparseMerkleTreeImpl> {
   const treeHeight = Math.ceil(Math.log2(dataBlocks.length)) + 1 // The height should actually not be plus 1
   log('Creating tree of height:', treeHeight - 1)
-  const tree = getNewSMT(treeHeight)
+  const tree = await getNewSMT(treeHeight)
   for (let i = 0; i < dataBlocks.length; i++) {
     await tree.update(new BigNumber(i, 10), dataBlocks[i])
   }
   return tree
 }
 
-function getNewSMT(treeHeight: number): SparseMerkleTreeImpl {
-  return new SparseMerkleTreeImpl(
-    new BaseDB(new MemDown('') as any, 256),
-    undefined,
-    treeHeight
-  )
+async function getNewSMT(treeHeight: number): Promise<SparseMerkleTreeImpl> {
+  return SparseMerkleTreeImpl.create(newInMemoryDB(), undefined, treeHeight)
 }
 
 function makeRandomBlockOfSize(blockSize: number): string[] {

packages/contracts/test/rollup-chain-manager/RollupChain.spec.ts

@@ -384,7 +384,7 @@ describe('RollupChain', () => {
       const encodedPreStates = preStateObjects.map((obj) => abiEncodeState(obj))
       // Create the state tree
       const treeHeight = 32 // Default tree height
-      const stateTree = new SparseMerkleTreeImpl(
+      const stateTree = await SparseMerkleTreeImpl.create(
         new BaseDB(new MemDown('') as any, 256),
         undefined,
         treeHeight + 1

packages/core/src/app/block-production/merkle-tree.ts

@@ -37,20 +37,34 @@ export class SparseMerkleTreeImpl implements SparseMerkleTree {
   private readonly hashFunction: (Buffer) => Buffer
   private readonly hashBuffer: Buffer = Buffer.alloc(64)
 
-  constructor(
-    private readonly db: DB,
+  public static async create(
+    db: DB,
     rootHash?: Buffer,
-    private readonly height: number = 160,
+    height: number = 160,
+    hashFunction = keccak256
+  ): Promise<SparseMerkleTreeImpl> {
+    assert(!rootHash || rootHash.length === 32, 'Root hash must be 32 bytes')
+
+    const tree = new SparseMerkleTreeImpl(db, height, hashFunction)
+
+    await tree.init(rootHash)
+    return tree
+  }
+
+  private constructor(
+    private db: DB,
+    private height: number = 160,
     hashFunction: HashFunction = keccak256
   ) {
-    assert(!rootHash || rootHash.length === 32, 'Root hash must be 32 bytes')
     assert(height > 0, 'SMT height needs to be > 0')
 
     // TODO: Hack for now -- change everything to string if/when it makes sense
     this.hashFunction = (buff: Buffer) =>
       Buffer.from(hashFunction(buff.toString('hex')), 'hex')
+  }
 
-    this.populateZeroHashesAndRoot(rootHash)
+  private async init(rootHash?: Buffer): Promise<void> {
+    await this.populateZeroHashesAndRoot(rootHash)
   }
 
   public getHeight(): number {
@@ -533,7 +547,7 @@ export class SparseMerkleTreeImpl implements SparseMerkleTree {
    *
    * @param rootHash The optional root hash to assign the tree
    */
-  private populateZeroHashesAndRoot(rootHash?: Buffer): void {
+  private async populateZeroHashesAndRoot(rootHash?: Buffer): Promise<void> {
     const hashes: Buffer[] = [
       this.hashFunction(SparseMerkleTreeImpl.emptyBuffer),
     ]
@@ -545,7 +559,34 @@ export class SparseMerkleTreeImpl implements SparseMerkleTree {
     }
 
     this.zeroHashes = hashes.reverse()
-    this.root = this.createNode(rootHash || this.zeroHashes[0], undefined, ZERO)
+
+    if (!!rootHash) {
+      log.info(
+        `Attempting to initialize SMT with root hash ${rootHash.toString(
+          'hex'
+        )}`
+      )
+      this.root = await this.getNode(rootHash, ZERO)
+    }
+
+    if (!this.root) {
+      this.root = this.createNode(
+        rootHash || this.zeroHashes[0],
+        undefined,
+        ZERO
+      )
+      log.info(
+        `Initialized Sparse Merkle Tree with root ${(
+          rootHash || this.zeroHashes[0]
+        ).toString('hex')}`
+      )
+    } else {
+      log.info(
+        `Initialized Sparse Merkle Tree with root ${this.root.hash.toString(
+          'hex'
+        )}`
+      )
+    }
   }
 
   /**

packages/core/src/app/ovm/deciders/merkle-inclusion-proof-decider.ts

@@ -15,7 +15,7 @@ export class MerkleInclusionProofDecider implements Decider {
     input: MerkleInclusionProofDeciderInput,
     _noCache?: boolean
   ): Promise<Decision> {
-    const tree = new SparseMerkleTreeImpl(
+    const tree = await SparseMerkleTreeImpl.create(
       newInMemoryDB(256),
       input.merkleProof.rootHash,
       input.merkleProof.siblings.length + 1

packages/core/test/app/block-production/merkle-tree.spec.ts

@@ -61,7 +61,7 @@ const createAndVerifyEmptyTreeDepthWithDepth = async (
   key: BigNumber,
   depth: number
 ): Promise<SparseMerkleTree> => {
-  const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+  const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
     db,
     undefined,
     depth,
@@ -117,22 +117,22 @@ describe('SparseMerkleTreeImpl', () => {
 
   describe('Constructor', () => {
     it('should construct without error', async () => {
-      new SparseMerkleTreeImpl(db)
+      await SparseMerkleTreeImpl.create(db)
     })
 
     it('accepts a non-empty root hash', async () => {
-      new SparseMerkleTreeImpl(db, Buffer.alloc(32).fill('root', 0))
+      await SparseMerkleTreeImpl.create(db, Buffer.alloc(32).fill('root', 0))
     })
 
     it('throws if root is not 32 bytes', async () => {
-      TestUtils.assertThrows(() => {
-        new SparseMerkleTreeImpl(db, Buffer.alloc(31).fill('root', 0))
+      await TestUtils.assertThrowsAsync(async () => {
+        await SparseMerkleTreeImpl.create(db, Buffer.alloc(31).fill('root', 0))
       }, assert.AssertionError)
     })
 
     it('throws if height is < 0', async () => {
-      TestUtils.assertThrows(() => {
-        new SparseMerkleTreeImpl(db, undefined, -1)
+      await TestUtils.assertThrowsAsync(async () => {
+        await SparseMerkleTreeImpl.create(db, undefined, -1)
       }, assert.AssertionError)
     })
   })
@@ -161,7 +161,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('fails on invalid proof for empty root', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         2,
@@ -189,7 +189,7 @@ describe('SparseMerkleTreeImpl', () => {
           .fill(bufferHashFunction(SparseMerkleTreeImpl.emptyBuffer), 32)
       )
 
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         root,
         2,
@@ -217,7 +217,7 @@ describe('SparseMerkleTreeImpl', () => {
           .fill(bufferHashFunction(value), 32)
       )
 
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         root,
         2,
@@ -245,7 +245,7 @@ describe('SparseMerkleTreeImpl', () => {
           .fill(bufferHashFunction(SparseMerkleTreeImpl.emptyBuffer), 32)
       )
 
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         root,
         2,
@@ -268,7 +268,7 @@ describe('SparseMerkleTreeImpl', () => {
 
   describe('update', () => {
     it('updates empty tree', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -289,7 +289,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('updates empty tree at key 1', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -311,7 +311,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('updates empty tree at key 2', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -333,7 +333,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('updates empty tree at key 3', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -363,7 +363,7 @@ describe('SparseMerkleTreeImpl', () => {
         zh  zh  zh  zh        A  zh  zh  zh     A    D  zh  zh
       */
 
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -414,7 +414,7 @@ describe('SparseMerkleTreeImpl', () => {
         zh  zh  zh  zh        A  zh  zh  zh     A    zh  D  zh
       */
 
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -460,7 +460,7 @@ describe('SparseMerkleTreeImpl', () => {
 
   describe('batchUpdate', () => {
     it('updates 2 values', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -516,7 +516,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('updates 3 values', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -591,7 +591,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('updates 4 values', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -687,7 +687,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('fails if one proof fails', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -802,7 +802,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('gets merkle proof for non-empty tree', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -829,7 +829,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('gets merkle proof for non-empty siblings 0 & 1', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -883,7 +883,7 @@ describe('SparseMerkleTreeImpl', () => {
     })
 
     it('gets merkle proof for non-empty siblings 0 & 2', async () => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         3,
@@ -949,7 +949,7 @@ describe('SparseMerkleTreeImpl', () => {
       numUpdates: number,
       keyRange: number
     ): Promise<void> => {
-      const tree: SparseMerkleTree = new SparseMerkleTreeImpl(
+      const tree: SparseMerkleTree = await SparseMerkleTreeImpl.create(
         db,
         undefined,
         treeHeight,

packages/core/test/app/ovm/deciders/merkle-inclusion-proof-decider.spec.ts

@@ -18,7 +18,7 @@ describe('MerkleTreeInclusionProofDecider', () => {
     const leafValue: Buffer = Buffer.from('Leaf value')
 
     it('should return true when inclusion proof is valid', async () => {
-      const merkleTree: SparseMerkleTreeImpl = new SparseMerkleTreeImpl(
+      const merkleTree: SparseMerkleTreeImpl = await SparseMerkleTreeImpl.create(
         newInMemoryDB(256)
       )
       assert(
@@ -47,7 +47,7 @@ describe('MerkleTreeInclusionProofDecider', () => {
     })
 
     it('should return true when inclusion proof is valid for 32-height tree', async () => {
-      const merkleTree: SparseMerkleTreeImpl = new SparseMerkleTreeImpl(
+      const merkleTree: SparseMerkleTreeImpl = await SparseMerkleTreeImpl.create(
         newInMemoryDB(256),
         undefined,
         32
@@ -80,7 +80,7 @@ describe('MerkleTreeInclusionProofDecider', () => {
 
     it('should return true when inclusion proof is valid for different key', async () => {
       const key: BigNumber = new BigNumber(10)
-      const merkleTree: SparseMerkleTreeImpl = new SparseMerkleTreeImpl(
+      const merkleTree: SparseMerkleTreeImpl = await SparseMerkleTreeImpl.create(
         newInMemoryDB(256)
       )
       assert(
@@ -110,7 +110,7 @@ describe('MerkleTreeInclusionProofDecider', () => {
 
     it('should return false when inclusion proof is invalid', async () => {
       const key: BigNumber = new BigNumber(10)
-      const merkleTree: SparseMerkleTreeImpl = new SparseMerkleTreeImpl(
+      const merkleTree: SparseMerkleTreeImpl = await SparseMerkleTreeImpl.create(
         newInMemoryDB(256)
       )
       assert(