provider: use fallback provider helper

Allow the DTL to sync from multiple web3 backends using
the `ethers.providers.FallbackProvider`. Multiple URLs
can be passed through as a comma delimited string to
configure multiple providers.

A helper function is added to `core-utils` to allow
easy configuration between services. This PR only introduces
the usage of the fallback provider into the DTL. In the
future, it should be added to other services that query L1
as well.

.changeset/eleven-moles-pull.md

+---
+'@eth-optimism/core-utils': patch
+'@eth-optimism/data-transport-layer': patch
+---
+
+Add fallback provider support to DTL using helper function in core-utils

packages/core-utils/package.json

@@ -47,6 +47,7 @@
   },
   "dependencies": {
     "@ethersproject/abstract-provider": "^5.4.1",
+    "@ethersproject/providers": "^5.4.5",
     "ethers": "^5.4.5",
     "lodash": "^4.17.21"
   }

packages/core-utils/src/index.ts

@@ -6,3 +6,4 @@ export * from './events'
 export * from './batches'
 export * from './bcfg'
 export * from './fees'
+export * from './provider'

packages/core-utils/src/provider.ts

+/**
+ * Provider Utilities
+ */
+
+import { ethers } from 'ethers'
+import { Provider } from '@ethersproject/providers'
+
+// Copied from @ethersproject/providers since it is not
+// currently exported
+export interface FallbackProviderConfig {
+  // The Provider
+  provider: Provider
+  // The priority to favour this Provider; higher values are used first
+  priority?: number
+  // Timeout before also triggering the next provider; this does not stop
+  // this provider and if its result comes back before a quorum is reached
+  // it will be incorporated into the vote
+  // - lower values will cause more network traffic but may result in a
+  //   faster retult.
+  stallTimeout?: number
+  // How much this provider contributes to the quorum; sometimes a specific
+  // provider may be more reliable or trustworthy than others, but usually
+  // this should be left as the default
+  weight?: number
+}
+
+export const FallbackProvider = (config: string | FallbackProviderConfig[]) => {
+  const configs = []
+  if (typeof config === 'string') {
+    const urls = config.split(',')
+    for (const [i, url] of urls.entries()) {
+      configs.push({
+        priority: i,
+        provider: new ethers.providers.StaticJsonRpcProvider(url),
+      })
+    }
+    return new ethers.providers.FallbackProvider(configs)
+  }
+  return new ethers.providers.FallbackProvider(config)
+}

packages/data-transport-layer/src/services/l1-ingestion/service.ts

 /* Imports: External */
-import { fromHexString } from '@eth-optimism/core-utils'
+import { fromHexString, FallbackProvider } from '@eth-optimism/core-utils'
 import { BaseService, Metrics } from '@eth-optimism/common-ts'
-import { StaticJsonRpcProvider } from '@ethersproject/providers'
+import { StaticJsonRpcProvider, BaseProvider } from '@ethersproject/providers'
 import { LevelUp } from 'levelup'
 import { ethers, constants } from 'ethers'
 import { Gauge, Counter } from 'prom-client'
@@ -80,7 +80,7 @@ const optionSettings = {
   },
   l1RpcProvider: {
     validate: (val: any) => {
-      return validators.isUrl(val) || validators.isJsonRpcProvider(val)
+      return validators.isString(val) || validators.isJsonRpcProvider(val)
     },
   },
   l2ChainId: {
@@ -98,7 +98,7 @@ export class L1IngestionService extends BaseService<L1IngestionServiceOptions> {
   private state: {
     db: TransportDB
     contracts: OptimismContracts
-    l1RpcProvider: StaticJsonRpcProvider
+    l1RpcProvider: BaseProvider
     startingL1BlockNumber: number
   } = {} as any
 
@@ -107,10 +107,11 @@ export class L1IngestionService extends BaseService<L1IngestionServiceOptions> {
 
     this.l1IngestionMetrics = registerMetrics(this.metrics)
 
-    this.state.l1RpcProvider =
-      typeof this.options.l1RpcProvider === 'string'
-        ? new StaticJsonRpcProvider(this.options.l1RpcProvider)
-        : this.options.l1RpcProvider
+    if (typeof this.options.l1RpcProvider === 'string') {
+      this.state.l1RpcProvider = FallbackProvider(this.options.l1RpcProvider)
+    } else {
+      this.state.l1RpcProvider = this.options.l1RpcProvider
+    }
 
     this.logger.info('Using AddressManager', {
       addressManager: this.options.addressManager,

packages/data-transport-layer/src/types/event-handler-types.ts

-import { JsonRpcProvider } from '@ethersproject/providers'
+import { BaseProvider } from '@ethersproject/providers'
 import { BigNumber, Event } from 'ethers'
 
 import { TransportDB } from '../db/transport-db'
@@ -15,7 +15,7 @@ export type TypedEthersEvent<T> = Event & {
 
 export type GetExtraDataHandler<TEventArgs, TExtraData> = (
   event?: TypedEthersEvent<TEventArgs>,
-  l1RpcProvider?: JsonRpcProvider
+  l1RpcProvider?: BaseProvider
 ) => Promise<TExtraData>
 
 export type ParseEventHandler<TEventArgs, TExtraData, TParsedEvent> = (

packages/data-transport-layer/src/utils/contracts.ts

 /* Imports: External */
 import { constants, Contract, Signer } from 'ethers'
-import { JsonRpcProvider } from '@ethersproject/providers'
+import { BaseProvider } from '@ethersproject/providers'
 import { getContractInterface } from '@eth-optimism/contracts'
 
 export const loadContract = (
   name: string,
   address: string,
-  provider: JsonRpcProvider
+  provider: BaseProvider
 ): Contract => {
   return new Contract(address, getContractInterface(name) as any, provider)
 }
@@ -15,7 +15,7 @@ export const loadProxyFromManager = async (
   name: string,
   proxy: string,
   Lib_AddressManager: Contract,
-  provider: JsonRpcProvider
+  provider: BaseProvider
 ): Promise<Contract> => {
   const address = await Lib_AddressManager.getAddress(proxy)
 
@@ -36,7 +36,7 @@ export interface OptimismContracts {
 }
 
 export const loadOptimismContracts = async (
-  l1RpcProvider: JsonRpcProvider,
+  l1RpcProvider: BaseProvider,
   addressManagerAddress: string,
   signer?: Signer
 ): Promise<OptimismContracts> => {

yarn.lock

@@ -922,6 +922,31 @@
     bech32 "1.1.4"
     ws "7.4.6"
 
+"@ethersproject/providers@^5.4.5":
+  version "5.4.5"
+  resolved "https://registry.yarnpkg.com/@ethersproject/providers/-/providers-5.4.5.tgz#eb2ea2a743a8115f79604a8157233a3a2c832928"
+  integrity sha512-1GkrvkiAw3Fj28cwi1Sqm8ED1RtERtpdXmRfwIBGmqBSN5MoeRUHuwHPppMtbPayPgpFcvD7/Gdc9doO5fGYgw==
+  dependencies:
+    "@ethersproject/abstract-provider" "^5.4.0"
+    "@ethersproject/abstract-signer" "^5.4.0"
+    "@ethersproject/address" "^5.4.0"
+    "@ethersproject/basex" "^5.4.0"
+    "@ethersproject/bignumber" "^5.4.0"
+    "@ethersproject/bytes" "^5.4.0"
+    "@ethersproject/constants" "^5.4.0"
+    "@ethersproject/hash" "^5.4.0"
+    "@ethersproject/logger" "^5.4.0"
+    "@ethersproject/networks" "^5.4.0"
+    "@ethersproject/properties" "^5.4.0"
+    "@ethersproject/random" "^5.4.0"
+    "@ethersproject/rlp" "^5.4.0"
+    "@ethersproject/sha2" "^5.4.0"
+    "@ethersproject/strings" "^5.4.0"
+    "@ethersproject/transactions" "^5.4.0"
+    "@ethersproject/web" "^5.4.0"
+    bech32 "1.1.4"
+    ws "7.4.6"
+
 "@ethersproject/random@5.4.0", "@ethersproject/random@^5.0.0", "@ethersproject/random@^5.4.0":
   version "5.4.0"
   resolved "https://registry.yarnpkg.com/@ethersproject/random/-/random-5.4.0.tgz#9cdde60e160d024be39cc16f8de3b9ce39191e16"