service.ts

import {
  BaseServiceV2,
  StandardOptions,
  ExpressRouter,
  Gauge,
  validators,
  waitForProvider,
} from '@eth-optimism/common-ts'
import { CrossChainMessenger } from '@eth-optimism/sdk'
import { getChainId, sleep } from '@eth-optimism/core-utils'
import { Provider } from '@ethersproject/abstract-provider'
import { Event } from 'ethers'
import dateformat from 'dateformat'

import { version } from '../../package.json'

type Options = {
  l1RpcProvider: Provider
  l2RpcProvider: Provider
  startBlockNumber: number
  sleepTimeMs: number
}

type Metrics = {
  withdrawalsValidated: Gauge
  isDetectingForgeries: Gauge
  nodeConnectionFailures: Gauge
}

type State = {
  messenger: CrossChainMessenger
  highestUncheckedBlockNumber: number
  finalizationWindow: number
  forgeryDetected: boolean
}

export class WithdrawalMonitor extends BaseServiceV2<Options, Metrics, State> {
  constructor(options?: Partial<Options & StandardOptions>) {
    super({
      version,
      name: 'two-step-monitor',
      loop: true,
      options: {
        loopIntervalMs: 1000,
        ...options,
      },
      optionsSpec: {
        l1RpcProvider: {
          validator: validators.provider,
          desc: 'Provider for interacting with L1',
        },
        l2RpcProvider: {
          validator: validators.provider,
          desc: 'Provider for interacting with L2',
        },
        startBlockNumber: {
          validator: validators.num,
          default: -1,
          desc: 'L1 block number to start checking from',
          public: true,
        },
        sleepTimeMs: {
          validator: validators.num,
          default: 15000,
          desc: 'Time in ms to sleep when waiting for a node',
          public: true,
        },
      },
      metricsSpec: {
        withdrawalsValidated: {
          type: Gauge,
          desc: 'Latest L1 Block (checked and known)',
          labels: ['type'],
        },
        isDetectingForgeries: {
          type: Gauge,
          desc: '0 if state is ok. 1 or more if forged withdrawals are detected.',
        },
        nodeConnectionFailures: {
          type: Gauge,
          desc: 'Number of times node connection has failed',
          labels: ['layer', 'section'],
        },
      },
    })
  }

  async init(): Promise<void> {
    // Connect to L1.
    await waitForProvider(this.options.l1RpcProvider, {
      logger: this.logger,
      name: 'L1',
    })

    // Connect to L2.
    await waitForProvider(this.options.l2RpcProvider, {
      logger: this.logger,
      name: 'L2',
    })

    this.state.messenger = new CrossChainMessenger({
      l1SignerOrProvider: this.options.l1RpcProvider,
      l2SignerOrProvider: this.options.l2RpcProvider,
      l1ChainId: await getChainId(this.options.l1RpcProvider),
      l2ChainId: await getChainId(this.options.l2RpcProvider),
    })

    // Not detected by default.
    this.state.forgeryDetected = false

    // For now we'll just start take it from the env or the tip of the chain
    if (this.options.startBlockNumber === -1) {
      this.state.highestUncheckedBlockNumber =
        await this.options.l1RpcProvider.getBlockNumber()
    } else {
      this.state.highestUncheckedBlockNumber = this.options.startBlockNumber
    }

    this.logger.info(`starting L1 block height`, {
      startBlockNumber: this.state.highestUncheckedBlockNumber,
    })
  }

  // K8s healthcheck
  async routes(router: ExpressRouter): Promise<void> {
    router.get('/healthz', async (req, res) => {
      return res.status(200).json({
        ok: !this.state.forgeryDetected,
      })
    })
  }

  async main(): Promise<void> {
    // Get current block number
    let latestL1BlockNumber: number
    try {
      latestL1BlockNumber = await this.options.l1RpcProvider.getBlockNumber()
    } catch (err) {
      this.logger.error(`got error when connecting to node`, {
        error: err,
        node: 'l1',
        section: 'getBlockNumber',
      })
      this.metrics.nodeConnectionFailures.inc({
        layer: 'l1',
        section: 'getBlockNumber',
      })
      await sleep(this.options.sleepTimeMs)
      return
    }

    // See if we have a new unchecked block
    if (latestL1BlockNumber <= this.state.highestUncheckedBlockNumber) {
      // The RPC provider is behind us, wait a bit
      await sleep(this.options.sleepTimeMs)
      return
    }

    this.logger.info(`checking recent blocks`, {
      fromBlockNumber: this.state.highestUncheckedBlockNumber,
      toBlockNumber: latestL1BlockNumber,
    })

    // Perform the check
    let proofEvents: Event[]
    try {
      // The query includes events in the blockNumbers given as the last two arguments
      proofEvents =
        await this.state.messenger.contracts.l1.OptimismPortal.queryFilter(
          this.state.messenger.contracts.l1.OptimismPortal.filters.WithdrawalProven(),
          this.state.highestUncheckedBlockNumber,
          latestL1BlockNumber
        )
    } catch (err) {
      this.logger.error(`got error when connecting to node`, {
        error: err,
        node: 'l1',
        section: 'querying for WithdrawalProven events',
      })
      this.metrics.nodeConnectionFailures.inc({
        layer: 'l1',
        section: 'querying for WithdrawalProven events',
      })
      // connection error, wait then restart
      await sleep(this.options.sleepTimeMs)
      return
    }

    for (const proofEvent of proofEvents) {
      const exists =
        await this.state.messenger.contracts.l2.BedrockMessagePasser.sentMessages(
          proofEvent.args.withdrawalHash
        )
      const provenAt = `${
        (dateformat(
          new Date(
            (await this.options.l1RpcProvider.getBlock(proofEvent.blockHash))
              .timestamp * 1000
          )
        ),
        'mmmm dS, yyyy, h:MM:ss TT',
        true)
      } UTC`
      if (exists) {
        this.metrics.withdrawalsValidated.inc()
        this.logger.info(`valid withdrawal`, {
          withdrawalHash: proofEvent.args.withdrawalHash,
          provenAt,
        })
      } else {
        this.logger.error(`withdrawalHash not seen on L2`, {
          withdrawalHash: proofEvent.args.withdrawalHash,
          provenAt,
        })
        this.state.forgeryDetected = true
        this.metrics.isDetectingForgeries.set(1)
        return
      }
    }

    this.state.highestUncheckedBlockNumber = latestL1BlockNumber + 1

    // If we got through the above without throwing an error, we should be fine to reset.
    this.state.forgeryDetected = false
    this.metrics.isDetectingForgeries.set(0)
  }
}

if (require.main === module) {
  const service = new WithdrawalMonitor()
  service.run()
}