feat(mon): create balance-mon service

Creates a new balance-mon service inside the chain-mon package. This
service is intended to replace the legacy balance-monitor package that
relied on Forta.

.changeset/ninety-schools-work.md

+---
+'@eth-optimism/chain-mon': minor
+---
+
+Introduces the balance-mon service to chain-mon.

.github/workflows/publish-canary.yml

@@ -18,6 +18,7 @@ jobs:
       l2geth: ${{ steps.packages.outputs.l2geth }}
       message-relayer: ${{ steps.packages.outputs.message-relayer }}
       fault-detector: ${{ steps.packages.outputs.fault-detector }}
+      balance-mon: ${{ steps.packages.outputs.balance-mon }}
       drippie-mon: ${{ steps.packages.outputs.drippie-mon }}
       wd-mon: ${{ steps.packages.outputs.wd-mon }}
       data-transport-layer: ${{ steps.packages.outputs.data-transport-layer }}
@@ -230,6 +231,33 @@ jobs:
           push: true
           tags: ethereumoptimism/fault-detector:${{ needs.canary-publish.outputs.canary-docker-tag }}
 
+  balance-mon:
+    name: Publish Balance Monitor Version ${{ needs.canary-publish.outputs.canary-docker-tag }}
+    needs: canary-publish
+    if: needs.canary-publish.outputs.balance-mon != ''
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_ACCESS_TOKEN_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_ACCESS_TOKEN_SECRET }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          file: ./ops/docker/Dockerfile.packages
+          target: balance-mon
+          push: true
+          tags: ethereumoptimism/balance-mon:${{ needs.canary-publish.outputs.canary-docker-tag }}
+
   drippie-mon:
     name: Publish Drippie Monitor Version ${{ needs.canary-publish.outputs.canary-docker-tag }}
     needs: canary-publish

.github/workflows/release.yml

@@ -14,6 +14,7 @@ jobs:
       l2geth: ${{ steps.packages.outputs.l2geth }}
       message-relayer: ${{ steps.packages.outputs.message-relayer }}
       fault-detector: ${{ steps.packages.outputs.fault-detector }}
+      balance-mon: ${{ steps.packages.outputs.drippie-mon }}
       drippie-mon: ${{ steps.packages.outputs.drippie-mon }}
       wd-mon: ${{ steps.packages.outputs.wd-mon }}
       data-transport-layer: ${{ steps.packages.outputs.data-transport-layer }}
@@ -364,6 +365,33 @@ jobs:
           push: true
           tags: ethereumoptimism/wd-mon:${{ needs.release.outputs.wd-mon }},ethereumoptimism/wd-mon:latest
 
+  drippie-mon:
+    name: Publish Balance Monitor Version ${{ needs.release.outputs.balance-mon }}
+    needs: release
+    if: needs.release.outputs.balance-mon != ''
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_ACCESS_TOKEN_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_ACCESS_TOKEN_SECRET }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          file: ./ops/docker/Dockerfile.packages
+          target: balance-mon
+          push: true
+          tags: ethereumoptimism/balance-mon:${{ needs.release.outputs.balance-mon }},ethereumoptimism/balance-mon:latest
+
   drippie-mon:
     name: Publish Drippie Monitor Version ${{ needs.release.outputs.drippie-mon }}
     needs: release

ops/docker/Dockerfile.packages

@@ -117,6 +117,10 @@ FROM base as replica-healthcheck
 WORKDIR /opt/optimism/packages/replica-healthcheck
 ENTRYPOINT ["npm", "run", "start"]
 
+FROM base as balance-mon
+WORKDIR /opt/optimism/packages/chain-mon
+ENTRYPOINT ["npm", "run", "start:balance-mon"]
+
 FROM base as drippie-mon
 WORKDIR /opt/optimism/packages/chain-mon
 ENTRYPOINT ["npm", "run", "start:drippie-mon"]

packages/chain-mon/.env.example

+###############################################################################
+#                               ↓ balance-mon ↓                               #
+###############################################################################
+
+# RPC pointing to network to monitor balances on
+BALANCE_MON__RPC=
+
+# JSON array in the format [{ "address": <address>, "nickname": <nickname> }, ... ]
+BALANCE_MON__ACCOUNTS=
+
 ###############################################################################
 #                               ↓ drippie-mon ↓                               #
 ###############################################################################

packages/chain-mon/package.json

@@ -9,6 +9,7 @@
     "dist/*"
   ],
   "scripts": {
+    "start:balance-mon": "ts-node ./src/balance-mon/service.ts",
     "start:drippie-mon": "ts-node ./src/drippie-mon/service.ts",
     "start:wd-mon": "ts-node ./src/wd-mon/service.ts",
     "test:coverage": "echo 'No tests defined.'",

packages/chain-mon/src/balance-mon/service.ts

+import {
+  BaseServiceV2,
+  StandardOptions,
+  Gauge,
+  Counter,
+  validators,
+} from '@eth-optimism/common-ts'
+import { Provider } from '@ethersproject/abstract-provider'
+import { ethers } from 'ethers'
+
+import { version } from '../../package.json'
+
+type BalanceMonOptions = {
+  rpc: Provider
+  accounts: string
+}
+
+type BalanceMonMetrics = {
+  balances: Gauge
+  unexpectedRpcErrors: Counter
+}
+
+type BalanceMonState = {
+  accounts: Array<{ address: string; nickname: string }>
+}
+
+export class BalanceMonService extends BaseServiceV2<
+  BalanceMonOptions,
+  BalanceMonMetrics,
+  BalanceMonState
+> {
+  constructor(options?: Partial<BalanceMonOptions & StandardOptions>) {
+    super({
+      version,
+      name: 'balance-mon',
+      loop: true,
+      options: {
+        loopIntervalMs: 60_000,
+        ...options,
+      },
+      optionsSpec: {
+        rpc: {
+          validator: validators.provider,
+          desc: 'Provider for network to monitor balances on',
+        },
+        accounts: {
+          validator: validators.str,
+          desc: 'JSON array of [{ address, nickname }] to monitor balances of',
+          public: true,
+        },
+      },
+      metricsSpec: {
+        balances: {
+          type: Gauge,
+          desc: 'Balances of addresses',
+          labels: ['address', 'nickname'],
+        },
+        unexpectedRpcErrors: {
+          type: Counter,
+          desc: 'Number of unexpected RPC errors',
+          labels: ['section', 'name'],
+        },
+      },
+    })
+  }
+
+  protected async init(): Promise<void> {
+    this.state.accounts = JSON.parse(this.options.accounts)
+  }
+
+  protected async main(): Promise<void> {
+    for (const account of this.state.accounts) {
+      let balance: ethers.BigNumber
+      try {
+        balance = await this.options.rpc.getBalance(account.address)
+      } catch (err) {
+        this.logger.info(`got unexpected RPC error`, {
+          section: 'balances',
+          name: 'getBalance',
+          err,
+        })
+        this.metrics.unexpectedRpcErrors.inc({
+          section: 'balances',
+          name: 'getBalance',
+        })
+        continue
+      }
+
+      this.logger.info(`got balance`, {
+        address: account.address,
+        nickname: account.nickname,
+        balance: balance.toString(),
+      })
+
+      // Parse the balance as an integer instead of via toNumber() to avoid ethers throwing an
+      // an error. We might get rounding errors but we don't need perfect precision here, just a
+      // generally accurate sense for what the current balance is.
+      this.metrics.balances.set(
+        { address: account.address, nickname: account.nickname },
+        parseInt(balance.toString(), 10)
+      )
+    }
+  }
+}
+
+if (require.main === module) {
+  const service = new BalanceMonService()
+  service.run()
+}

packages/chain-mon/src/index.ts

+export * from './balance-mon/service'
 export * from './drippie-mon/service'
 export * from './wd-mon/service'