fix(dtl): improve slow blocking JSON parsing that occurs during l2 sync (#1019)

The use of eth_getBlockRange returns a large response which is very
slow to parse in ethersjs, and can block the event loop for upwards
of multiple seconds.

When this happens, incoming http requests will likely timeout and fail.

Instead, we will parse the incoming http stream directly with the bfj
package, which yields the event loop periodically so that we don't
fail to serve requests.

.changeset/wet-falcons-talk.md

+---
+'@eth-optimism/data-transport-layer': patch
+---
+
+improve slow blocking JSON parsing that occurs during l2 sync

packages/data-transport-layer/package.json

@@ -30,6 +30,7 @@
     "@sentry/tracing": "^6.3.1",
     "@types/express": "^4.17.11",
     "bcfg": "^0.1.6",
+    "bfj": "^7.0.2",
     "browser-or-node": "^1.3.0",
     "cors": "^2.8.5",
     "dotenv": "^8.2.0",
@@ -49,6 +50,7 @@
     "@types/levelup": "^4.3.0",
     "@types/mocha": "^8.2.2",
     "@types/node-fetch": "^2.5.8",
+    "@types/workerpool": "^6.0.0",
     "chai": "^4.3.4",
     "chai-as-promised": "^7.1.1",
     "hardhat": "^2.2.1",

packages/data-transport-layer/src/services/l2-ingestion/service.ts

@@ -3,6 +3,8 @@ import { BaseService } from '@eth-optimism/common-ts'
 import { JsonRpcProvider } from '@ethersproject/providers'
 import { BigNumber } from 'ethers'
 import { LevelUp } from 'levelup'
+import axios from 'axios';
+import bfj from 'bfj';
 
 /* Imports: Internal */
 import { TransportDB } from '../../db/transport-db'
@@ -168,11 +170,27 @@ export class L2IngestionService extends BaseService<L2IngestionServiceOptions> {
         )
       })
     } else {
-      blocks = await this.state.l2RpcProvider.send('eth_getBlockRange', [
-        toRpcHexString(startBlockNumber),
-        toRpcHexString(endBlockNumber),
-        true,
-      ])
+      // This request returns a large response.  Parsing it into JSON inside the ethers library is
+      // quite slow, and can block the event loop for upwards of multiple seconds.  When this happens,
+      // incoming http requests will likely timeout and fail.
+      // Instead, we will parse the incoming http stream directly with the bfj package, which yields
+      // the event loop periodically so that we don't fail to serve requests.
+      const req = {
+        jsonrpc: '2.0',
+        method: 'eth_getBlockRange',
+        params: [
+          toRpcHexString(startBlockNumber),
+          toRpcHexString(endBlockNumber),
+          true,
+        ],
+        id: '1',
+      };
+
+      const resp = await axios.post(this.state.l2RpcProvider.connection.url, req, {responseType: 'stream'});
+      const respJson = await bfj.parse(resp.data, { 
+        yieldRate: 4096 // this yields abit more often than the default of 16384
+      });
+      const blocks = respJson.data;
     }
 
     for (const block of blocks) {

yarn.lock

@@ -2601,6 +2601,13 @@
     "@types/bn.js" "*"
     "@types/underscore" "*"
 
+"@types/workerpool@^6.0.0":
+  version "6.0.0"
+  resolved "https://registry.yarnpkg.com/@types/workerpool/-/workerpool-6.0.0.tgz#068c31191f7df9b3d49ebe348b1eeb601e75e2d3"
+  integrity sha512-BjbKVHFBWblQ3vZ5yFq29kbM2TsaUaTOwYgVxqnNjMrT6CktVF8AvMxOJZgHGgNbAzP4z8DK+EshyZcYpdvAhQ==
+  dependencies:
+    "@types/node" "*"
+
 "@types/yargs-parser@*":
   version "20.2.0"
   resolved "https://registry.yarnpkg.com/@types/yargs-parser/-/yargs-parser-20.2.0.tgz#dd3e6699ba3237f0348cd085e4698780204842f9"
@@ -3657,6 +3664,16 @@ better-path-resolve@1.0.0:
   dependencies:
     is-windows "^1.0.0"
 
+bfj@^7.0.2:
+  version "7.0.2"
+  resolved "https://registry.yarnpkg.com/bfj/-/bfj-7.0.2.tgz#1988ce76f3add9ac2913fd8ba47aad9e651bfbb2"
+  integrity sha512-+e/UqUzwmzJamNF50tBV6tZPTORow7gQ96iFow+8b562OdMpEK0BcJEq2OSPEDmAbSMBQ7PKZ87ubFkgxpYWgw==
+  dependencies:
+    bluebird "^3.5.5"
+    check-types "^11.1.1"
+    hoopy "^0.1.4"
+    tryer "^1.0.1"
+
 bignumber.js@^9.0.0, bignumber.js@^9.0.1:
   version "9.0.1"
   resolved "https://registry.yarnpkg.com/bignumber.js/-/bignumber.js-9.0.1.tgz#8d7ba124c882bfd8e43260c67475518d0689e4e5"
@@ -3711,7 +3728,7 @@ blakejs@^1.1.0:
   resolved "https://registry.yarnpkg.com/blakejs/-/blakejs-1.1.0.tgz#69df92ef953aa88ca51a32df6ab1c54a155fc7a5"
   integrity sha1-ad+S75U6qIylGjLfarHFShVfx6U=
 
-bluebird@^3.5.0, bluebird@^3.5.2, bluebird@^3.5.3, bluebird@^3.7.2:
+bluebird@^3.5.0, bluebird@^3.5.2, bluebird@^3.5.3, bluebird@^3.5.5, bluebird@^3.7.2:
   version "3.7.2"
   resolved "https://registry.yarnpkg.com/bluebird/-/bluebird-3.7.2.tgz#9f229c15be272454ffa973ace0dbee79a1b0c36f"
   integrity sha512-XpNj6GDQzdfW+r2Wnn7xiSAd7TM3jzkxGXBGTtWKuSXv1xUV+azxAm8jdWZN06QTQk+2N2XB9jRDkvbmQmcRtg==
@@ -4190,6 +4207,11 @@ check-error@^1.0.2:
   resolved "https://registry.yarnpkg.com/check-error/-/check-error-1.0.2.tgz#574d312edd88bb5dd8912e9286dd6c0aed4aac82"
   integrity sha1-V00xLt2Iu13YkS6Sht1sCu1KrII=
 
+check-types@^11.1.1:
+  version "11.1.2"
+  resolved "https://registry.yarnpkg.com/check-types/-/check-types-11.1.2.tgz#86a7c12bf5539f6324eb0e70ca8896c0e38f3e2f"
+  integrity sha512-tzWzvgePgLORb9/3a0YenggReLKAIb2owL03H2Xdoe5pKcUyWRSEQ8xfCar8t2SIAuEDwtmx2da1YB52YuHQMQ==
+
 checkpoint-store@^1.1.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/checkpoint-store/-/checkpoint-store-1.1.0.tgz#04e4cb516b91433893581e6d4601a78e9552ea06"
@@ -7304,6 +7326,11 @@ home-or-tmp@^2.0.0:
     os-homedir "^1.0.0"
     os-tmpdir "^1.0.1"
 
+hoopy@^0.1.4:
+  version "0.1.4"
+  resolved "https://registry.yarnpkg.com/hoopy/-/hoopy-0.1.4.tgz#609207d661100033a9a9402ad3dea677381c1b1d"
+  integrity sha512-HRcs+2mr52W0K+x8RzcLzuPPmVIKMSv97RGHy0Ea9y/mpcaK+xTrjICA04KAHi4GRzxliNqNJEFYWHghy3rSfQ==
+
 hosted-git-info@^2.1.4, hosted-git-info@^2.6.0:
   version "2.8.8"
   resolved "https://registry.yarnpkg.com/hosted-git-info/-/hosted-git-info-2.8.8.tgz#7539bd4bc1e0e0a895815a2e0262420b12858488"
@@ -12743,6 +12770,11 @@ trim-right@^1.0.1:
   resolved "https://registry.yarnpkg.com/true-case-path/-/true-case-path-2.2.1.tgz#c5bf04a5bbec3fd118be4084461b3a27c4d796bf"
   integrity sha512-0z3j8R7MCjy10kc/g+qg7Ln3alJTodw9aDuVWZa3uiWqfuBMKeAeP2ocWcxoyM3D73yz3Jt/Pu4qPr4wHSdB/Q==
 
+tryer@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/tryer/-/tryer-1.0.1.tgz#f2c85406800b9b0f74c9f7465b81eaad241252f8"
+  integrity sha512-c3zayb8/kWWpycWYg87P71E1S1ZL6b6IJxfb5fvsUgsf0S2MVGaDhDXXjDMpdCpfWXqptc+4mXwmiy1ypXqRAA==
+
 ts-essentials@^1.0.0, ts-essentials@^1.0.2:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/ts-essentials/-/ts-essentials-1.0.4.tgz#ce3b5dade5f5d97cf69889c11bf7d2da8555b15a"