feat(chain-mon): monitor safe nonce as a metric

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

@@ -6,7 +6,7 @@ import {
   validators,
 } from '@eth-optimism/common-ts'
 import { Provider } from '@ethersproject/abstract-provider'
-import { ethers } from 'ethers'
+import { BigNumber, ethers } from 'ethers'
 
 import { version } from '../../package.json'
 
@@ -17,11 +17,12 @@ type BalanceMonOptions = {
 
 type BalanceMonMetrics = {
   balances: Gauge
+  safeNonces: Gauge
   unexpectedRpcErrors: Counter
 }
 
 type BalanceMonState = {
-  accounts: Array<{ address: string; nickname: string }>
+  accounts: Array<{ address: string; nickname: string; safe: boolean }>
 }
 
 export class BalanceMonService extends BaseServiceV2<
@@ -45,7 +46,7 @@ export class BalanceMonService extends BaseServiceV2<
         },
         accounts: {
           validator: validators.str,
-          desc: 'JSON array of [{ address, nickname }] to monitor balances of',
+          desc: 'JSON array of [{ address, nickname, safe }] to monitor balances and nonces of',
           public: true,
         },
       },
@@ -55,6 +56,11 @@ export class BalanceMonService extends BaseServiceV2<
           desc: 'Balances of addresses',
           labels: ['address', 'nickname'],
         },
+        safeNonces: {
+          type: Gauge,
+          desc: 'Safe nonce',
+          labels: ['address', 'nickname'],
+        },
         unexpectedRpcErrors: {
           type: Counter,
           desc: 'Number of unexpected RPC errors',
@@ -73,6 +79,19 @@ export class BalanceMonService extends BaseServiceV2<
       let balance: ethers.BigNumber
       try {
         balance = await this.options.rpc.getBalance(account.address)
+        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)
+        )
       } catch (err) {
         this.logger.info(`got unexpected RPC error`, {
           section: 'balances',
@@ -83,22 +102,40 @@ export class BalanceMonService extends BaseServiceV2<
           section: 'balances',
           name: 'getBalance',
         })
-        continue
       }
 
-      this.logger.info(`got balance`, {
-        address: account.address,
-        nickname: account.nickname,
-        balance: balance.toString(),
-      })
+      // Get the safe nonce to report
+      if (account.safe) {
+        let safeNonce: ethers.BigNumber
+        try {
+          safeNonce = BigNumber.from(
+            await this.options.rpc.call({
+              to: account.address,
+              data: '0xaffed0e0', // call the nonce() function in the safe contract
+            })
+          )
+          this.logger.info(`got nonce`, {
+            address: account.address,
+            nickname: account.nickname,
+            nonce: safeNonce.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)
-      )
+          this.metrics.safeNonces.set(
+            { address: account.address, nickname: account.nickname },
+            parseInt(safeNonce.toString(), 10)
+          )
+        } catch (err) {
+          this.logger.info(`got unexpected RPC error`, {
+            section: 'safeNonce',
+            name: 'getSafeNonce',
+            err,
+          })
+          this.metrics.unexpectedRpcErrors.inc({
+            section: 'safeNonce',
+            name: 'getSafeNonce',
+          })
+        }
+      }
     }
   }
 }