From 1a4343301cf6c9c73b4419b5de1d0dbaad2b9426 Mon Sep 17 00:00:00 2001
From: Bartek <bartlomiejkramek@outlook.com>
Date: Wed, 4 Oct 2023 16:47:04 +0200
Subject: [PATCH] perf: cache l2 block range (#343)

---
 package.json                          |  1 +
 src/lib/message/L2ToL1MessageNitro.ts | 64 ++++++++++++++++++++++++++-
 yarn.lock                             | 12 +++++
 3 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/package.json b/package.json
index fd578fb86f..7c558b88f1 100644
--- a/package.json
+++ b/package.json
@@ -49,6 +49,7 @@
     "@ethersproject/address": "^5.0.8",
     "@ethersproject/bignumber": "^5.1.1",
     "@ethersproject/bytes": "^5.0.8",
+    "async-mutex": "^0.4.0",
     "ethers": "^5.1.0"
   },
   "devDependencies": {
diff --git a/src/lib/message/L2ToL1MessageNitro.ts b/src/lib/message/L2ToL1MessageNitro.ts
index 2ef4711d55..a744061ec8 100644
--- a/src/lib/message/L2ToL1MessageNitro.ts
+++ b/src/lib/message/L2ToL1MessageNitro.ts
@@ -32,6 +32,7 @@ import { NodeInterface__factory } from '../abi/factories/NodeInterface__factory'
 
 import { L2ToL1TxEvent } from '../abi/ArbSys'
 import { ContractTransaction, Overrides } from 'ethers'
+import { Mutex } from 'async-mutex'
 import { EventFetcher, FetchedEvent } from '../utils/eventFetcher'
 import { ArbSdkError } from '../dataEntities/errors'
 import {
@@ -61,6 +62,64 @@ const ASSERTION_CREATED_PADDING = 50
 // expected number of L1 blocks that it takes for a validator to confirm an L1 block after the node deadline is passed
 const ASSERTION_CONFIRMED_PADDING = 20
 
+const l2BlockRangeCache: { [key in string]: (number | undefined)[] } = {}
+const mutex = new Mutex()
+
+function getL2BlockRangeCacheKey({
+  l2ChainId,
+  l1BlockNumber,
+}: {
+  l2ChainId: number
+  l1BlockNumber: number
+}) {
+  return `${l2ChainId}-${l1BlockNumber}`
+}
+
+function setL2BlockRangeCache(key: string, value: (number | undefined)[]) {
+  l2BlockRangeCache[key] = value
+}
+
+async function getBlockRangesForL1BlockWithCache({
+  l1Provider,
+  l2Provider,
+  forL1Block,
+}: {
+  l1Provider: JsonRpcProvider
+  l2Provider: JsonRpcProvider
+  forL1Block: number
+}) {
+  const l2ChainId = (await l2Provider.getNetwork()).chainId
+  const key = getL2BlockRangeCacheKey({
+    l2ChainId,
+    l1BlockNumber: forL1Block,
+  })
+
+  if (l2BlockRangeCache[key]) {
+    return l2BlockRangeCache[key]
+  }
+
+  // implements a lock that only fetches cache once
+  const release = await mutex.acquire()
+
+  // if cache has been acquired while awaiting the lock
+  if (l2BlockRangeCache[key]) {
+    release()
+    return l2BlockRangeCache[key]
+  }
+
+  try {
+    const l2BlockRange = await getBlockRangesForL1Block({
+      forL1Block,
+      provider: l1Provider,
+    })
+    setL2BlockRangeCache(key, l2BlockRange)
+  } finally {
+    release()
+  }
+
+  return l2BlockRangeCache[key]
+}
+
 /**
  * Base functionality for nitro L2->L1 messages
  */
@@ -212,9 +271,10 @@ export class L2ToL1MessageReaderNitro extends L2ToL1MessageNitro {
     // If L1 is Arbitrum, then L2 is an Orbit chain.
     if (await isArbitrumChain(this.l1Provider)) {
       try {
-        const l2BlockRange = await getBlockRangesForL1Block({
+        const l2BlockRange = await getBlockRangesForL1BlockWithCache({
+          l1Provider: this.l1Provider as JsonRpcProvider,
+          l2Provider: l2Provider as JsonRpcProvider,
           forL1Block: createdAtBlock.toNumber(),
-          provider: this.l1Provider as JsonRpcProvider,
         })
         const startBlock = l2BlockRange[0]
         const endBlock = l2BlockRange[1]
diff --git a/yarn.lock b/yarn.lock
index 238f1c19df..dd40c14fe6 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1723,6 +1723,13 @@ async-eventemitter@^0.2.4:
   dependencies:
     async "^2.4.0"
 
+async-mutex@^0.4.0:
+  version "0.4.0"
+  resolved "https://registry.yarnpkg.com/async-mutex/-/async-mutex-0.4.0.tgz#ae8048cd4d04ace94347507504b3cf15e631c25f"
+  integrity sha512-eJFZ1YhRR8UN8eBLoNzcDPcy/jqjsg6I1AP+KvWQX80BqOSW1oJPJXDylPUEeMr2ZQvHgnQ//Lp6f3RQ1zI7HA==
+  dependencies:
+    tslib "^2.4.0"
+
 async@^2.4.0:
   version "2.6.4"
   resolved "https://registry.yarnpkg.com/async/-/async-2.6.4.tgz#706b7ff6084664cd7eae713f6f965433b5504221"
@@ -5192,6 +5199,11 @@ tslib@^1.13.0, tslib@^1.8.1, tslib@^1.9.3:
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.14.1.tgz#cf2d38bdc34a134bcaf1091c41f6619e2f672d00"
   integrity sha512-Xni35NKzjgMrwevysHTCArtLDpPvye8zV/0E4EyYn43P7/7qvQwPh9BGkHewbMulVntbigmcT7rdX3BNo9wRJg==
 
+tslib@^2.4.0:
+  version "2.6.2"
+  resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.6.2.tgz#703ac29425e7b37cd6fd456e92404d46d1f3e4ae"
+  integrity sha512-AEYxH93jGFPn/a2iVAwW87VuUIkR1FVUKB77NwMF7nBTDkDrrT/Hpt/IrCJ0QXhW27jTBDcf5ZY7w6RiqTMw2Q==
+
 tslint@^6.1.3:
   version "6.1.3"
   resolved "https://registry.yarnpkg.com/tslint/-/tslint-6.1.3.tgz#5c23b2eccc32487d5523bd3a470e9aa31789d904"