From 36485bc0b32b061286a6c14cc981da436279b402 Mon Sep 17 00:00:00 2001
From: Santiago Palladino <santiago@aztecprotocol.com>
Date: Mon, 16 Dec 2024 20:26:57 -0300
Subject: [PATCH] fix: Race condition in block stream

Try fix a race condition in the L2 block stream:

```
[20:12:05.473] ERROR: pxe:block_stream Error processing block stream: Error: Block hash not found for block number 8
    at L2TipsStore.getL2Tip (/home/santiago/Projects/aztec3-packages-4/yarn-project/kv-store/src/stores/l2_tips_store.ts:42:13)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at L2TipsStore.getL2Tips (/home/santiago/Projects/aztec3-packages-4/yarn-project/kv-store/src/stores/l2_tips_store.ts:29:15)
    at L2BlockStream.work (/home/santiago/Projects/aztec3-packages-4/yarn-project/circuit-types/src/l2_block_downloader/l2_block_stream.ts:47:25)
    at Synchronizer.sync (/home/santiago/Projects/aztec3-packages-4/yarn-project/pxe/src/synchronizer/synchronizer.ts:88:5)
    at PXEService.simulateTx (/home/santiago/Projects/aztec3-packages-4/yarn-project/pxe/src/pxe_service/pxe_service.ts:501:7)
    at ContractFunctionInteraction.proveInternal (/home/santiago/Projects/aztec3-packages-4/yarn-project/aztec.js/src/contract/base_contract_interaction.ts:53:32)
    at /home/santiago/Projects/aztec3-packages-4/yarn-project/aztec.js/src/contract/base_contract_interaction.ts:78:31
    at SentTx.waitForReceipt (/home/santiago/Projects/aztec3-packages-4/yarn-project/aztec.js/src/contract/sent_tx.ts:100:20)
    at SentTx.wait (/home/santiago/Projects/aztec3-packages-4/yarn-project/aztec.js/src/contract/sent_tx.ts:67:21)
    at async Promise.all (index 0)
    at Object.<anonymous> (/home/santiago/Projects/aztec3-packages-4/yarn-project/end-to-end/src/benchmarks/bench_prover.test.ts:119:5)
```

Note that the issue the the L2 stream requesting the block hash for a
block number that it should know about. This can happen if the latest block
number is increased _before_ the block is saved. Storing the blocks
before bumping the number seems to fix it across several local runs.
---
 yarn-project/kv-store/src/stores/l2_tips_store.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/yarn-project/kv-store/src/stores/l2_tips_store.ts b/yarn-project/kv-store/src/stores/l2_tips_store.ts
index 149f7be80b39..33c513097e53 100644
--- a/yarn-project/kv-store/src/stores/l2_tips_store.ts
+++ b/yarn-project/kv-store/src/stores/l2_tips_store.ts
@@ -47,10 +47,10 @@ export class L2TipsStore implements L2BlockStreamEventHandler, L2BlockStreamLoca
   public async handleBlockStreamEvent(event: L2BlockStreamEvent): Promise<void> {
     switch (event.type) {
       case 'blocks-added':
-        await this.l2TipsStore.set('latest', event.blocks.at(-1)!.number);
         for (const block of event.blocks) {
           await this.l2BlockHashesStore.set(block.number, block.header.hash().toString());
         }
+        await this.l2TipsStore.set('latest', event.blocks.at(-1)!.number);
         break;
       case 'chain-pruned':
         await this.l2TipsStore.set('latest', event.blockNumber);