OP Stack Hooks

An OP Stack Mod for adding customisable transaction hooks to your OP Stack chain. Hook registration is permissioned in this mod, meaning hook registration is priviledged and only rollup deployers can add these.

Event hooks
Before block hook
Transaction hooks

See the diff with vanilla Optimism here.

Event hooks

Relay transaction events from Ethereum mainnet to your rollup, these events can then trigger additional contracts on your rollup or simply store data. Some novel ideas for event hooks include,

Chainlink price feeds, automatically relay price feed data to your rollup
Cross chain goverance, once votes pass and are executed on L1 these could be replayed on your rollup
Asset ownership tracking, replay asset ownership on your rollup

A hook can be added by calling addEventHook on the EventHookRegistry, a predeploy available at 0x420000000000000000000000000000000000001c.

Before block hook

Called before every block, giving priviledged access to block space for rollup deployers.

Transaction hooks

A superset of functionality offered by event hooks, allowing listeners to be registered on transactions filtered by a to or from address.

Quickstart

The best way to get started with this mod and register some hooks is to use the devnet. Following along with the below commands will get you setup with a hook in under five minutes.

We'll first setup our devnet,

make devnet-up-deploy

which will run both the L1 and L2 pieces of the rollup, super handy. After that's completed we'll set some variables to make deploying and interacting with our contracts a bit easier.

export L2=http://localhost:9545
export L1=http://localhost:8545
export PRIVATE_KEY=0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80

Bundled as part of this OP Stack Mod are some example contracts that show off the hook functionality. We'll deploy those and then send an event from L1 to L2 and record the output.

First deploy the L1 contract, and make sure you note down the address it was deployed to. We'll refer to this address as <EVENT_EMITTER> for the rest of this quickstart.

cd packages/contracts-bedrock
forge create --private-key $PRIVATE_KEY contracts/L1/hooks/ExampleEventEmitter.sol:ExampleEventEmitter --rpc-url $L1

Then deploy the L2 contract, and similarly make a note of the contract address. We'll refer to it as <EVENT_HOOK> for the rest of this quickstart.

forge create --private-key $PRIVATE_KEY contracts/L2/hooks/ExampleEventHook.sol:ExampleEventHook --rpc-url $L2

Now we need to register this hook on the on our hook registry,

cast send 0x420000000000000000000000000000000000001c "addEventHook(bytes32,address,address)" 0x906c0fc836aaccaf76ef8a4168843fbbb1d6fb940e6e045ed4d32c1bcefbc7c8 <EVENT_EMITTER> <EVENT_HOOK> --rpc-url $L2 --private-key $PRIVATE_KEY

The magic variable we just used, 0x906c0fc836aaccaf76ef8a4168843fbbb1d6fb940e6e045ed4d32c1bcefbc7c8, is the topic of the event we wish to register. This can be found in the ExampleEventEmitter, and is the result of hashing the event we're interested in, namely the ExampleEvent.

Now all we need to do is trigger an event on L1 and make sure the data was received on the L2.

cast send 0x0d6cd45Be79bc9A6Cf672D345d2855158C4fDdf1 "emitEvent()" --rpc-url $L1 --private-key $PRIVATE_KEY

Remember this example emitter emits an ever incrementing number, and the example hook simply stores this number. So if we check the counter value on L2, we should see the count variable was incremented,

cast call 0x5F7fAB0e5D73356Fd73624c8F43c0cAD76950C88 "getLastParsedCount()" --rpc-url $L2
0x0000000000000000000000000000000000000000000000000000000000000001

Optimism is Ethereum, scaled.

What is Optimism?

Optimism is a project dedicated to scaling Ethereum's technology and expanding its ability to coordinate people from across the world to build effective decentralized economies and governance systems. The Optimism Collective builds open-source software for running L2 blockchains and aims to address key governance and economic challenges in the wider cryptocurrency ecosystem. Optimism operates on the principle of impact=profit, the idea that individuals who positively impact the Collective should be proportionally rewarded with profit. Change the incentives and you change the world.

In this repository, you'll find numerous core components of the OP Stack, the decentralized software stack maintained by the Optimism Collective that powers Optimism and forms the backbone of blockchains like OP Mainnet and Base. Designed to be "aggressively open source," the OP Stack encourages you to explore, modify, extend, and test the code as needed. Although not all elements of the OP Stack are contained here, many of its essential components can be found within this repository. By collaborating on free, open software and shared standards, the Optimism Collective aims to prevent siloed software development and rapidly accelerate the development of the Ethereum ecosystem. Come contribute, build the future, and redefine power, together.

Documentation

If you want to build on top of OP Mainnet, refer to the Optimism Community Hub
If you want to build your own OP Stack based blockchain, refer to the OP Stack docs
If you want to contribute to the OP Stack, check out the Protocol Specs

Community

General discussion happens most frequently on the Optimism discord. Governance discussion can also be found on the Optimism Governance Forum.

Contributing

Read through CONTRIBUTING.md for a general overview of the contributing process for this repository. Use the Developer Quick Start to get your development environment set up to start working on the Optimism Monorepo. Then check out the list of Good First Issues to find something fun to work on!

Security Policy and Vulnerability Reporting

Please refer to the canonical Security Policy document for detailed information about how to report vulnerabilities in this codebase. Bounty hunters are encouraged to check out the Optimism Immunefi bug bounty program. The Optimism Immunefi program offers up to $2,000,042 for in-scope critical vulnerabilities.

The Bedrock Upgrade

OP Mainnet is currently preparing for its next major upgrade, Bedrock. You can find detailed specifications for the Bedrock upgrade within the specs folder in this repository.

Please note that a significant number of packages and folders within this repository are part of the Bedrock upgrade and are NOT currently running in production. Refer to the Directory Structure section below to understand which packages are currently running in production and which are intended for use as part of the Bedrock upgrade.

Directory Structure

~~ Production ~~
├── packages
│   ├── common-ts: Common tools for building apps in TypeScript
│   ├── contracts-bedrock: Bedrock smart contracts.
│   ├── contracts-periphery: Peripheral contracts for Optimism
│   ├── core-utils: Low-level utilities that make building Optimism easier
│   ├── chain-mon: Chain monitoring services
│   ├── fault-detector: Service for detecting Sequencer faults
│   ├── replica-healthcheck: Service for monitoring the health of a replica node
│   └── sdk: provides a set of tools for interacting with Optimism
├── op-bindings: Go bindings for Bedrock smart contracts.
├── op-batcher: L2-Batch Submitter, submits bundles of batches to L1
├── op-bootnode: Standalone op-node discovery bootnode
├── op-chain-ops: State surgery utilities
├── op-challenger: Dispute game challenge agent
├── op-e2e: End-to-End testing of all bedrock components in Go
├── op-exporter: Prometheus exporter client
├── op-heartbeat: Heartbeat monitor service
├── op-node: rollup consensus-layer client
├── op-program: Fault proof program
├── op-proposer: L2-Output Submitter, submits proposals to L1
├── op-service: Common codebase utilities
├── op-signer: Client signer
├── op-wheel: Database utilities
├── ops-bedrock: Bedrock devnet work
├── proxyd: Configurable RPC request router and proxy
└── specs: Specs of the rollup starting at the Bedrock upgrade

~~ Pre-BEDROCK ~~
├── packages
│   ├── common-ts: Common tools for building apps in TypeScript
│   ├── contracts-periphery: Peripheral contracts for Optimism
│   ├── core-utils: Low-level utilities that make building Optimism easier
│   ├── chain-mon: Chain monitoring services
│   ├── fault-detector: Service for detecting Sequencer faults
│   ├── replica-healthcheck: Service for monitoring the health of a replica node
│   └── sdk: provides a set of tools for interacting with Optimism
├── indexer: indexes and syncs transactions
├── op-exporter: A prometheus exporter to collect/serve metrics from an Optimism node
├── proxyd: Configurable RPC request router and proxy
└── technical-documents: audits and post-mortem documents

Branching Model

Active Branches

Branch	Status
master	Accepts PRs from `develop` when intending to deploy to production.
develop	Accepts PRs that are compatible with `master` OR from `release/X.X.X` branches.
release/X.X.X	Accepts PRs for all changes, particularly those not backwards compatible with `develop` and `master`.

Overview

This repository generally follows this Git branching model. Please read the linked post if you're planning to make frequent PRs into this repository.

Production branch

The production branch is master. The master branch contains the code for latest "stable" releases. Updates from master always come from the develop branch.

Development branch

The primary development branch is develop. develop contains the most up-to-date software that remains backwards compatible with the latest experimental network deployments. If you're making a backwards compatible change, please direct your pull request towards develop.

Changes to contracts within packages/contracts-bedrock/contracts are usually NOT considered backwards compatible and SHOULD be made against a release candidate branch. Some exceptions to this rule exist for cases in which we absolutely must deploy some new contract after a release candidate branch has already been fully deployed. If you're changing or adding a contract and you're unsure about which branch to make a PR into, default to using the latest release candidate branch. See below for info about release candidate branches.

Release candidate branches

Branches marked release/X.X.X are release candidate branches. Changes that are not backwards compatible and all changes to contracts within packages/contracts-bedrock/contracts MUST be directed towards a release candidate branch. Release candidates are merged into develop and then into master once they've been fully deployed. We may sometimes have more than one active release/X.X.X branch if we're in the middle of a deployment. See table in the Active Branches section above to find the right branch to target.

Releases

Changesets

We use changesets to mark packages for new releases. When merging commits to the develop branch you MUST include a changeset file if your change would require that a new version of a package be released.

To add a changeset, run the command pnpm changeset in the root of this monorepo. You will be presented with a small prompt to select the packages to be released, the scope of the release (major, minor, or patch), and the reason for the release. Comments within changeset files will be automatically included in the changelog of the package.

Triggering Releases

Releases can be triggered using the following process:

Create a PR that merges the develop branch into the master branch.
Wait for the auto-generated Version Packages PR to be opened (may take several minutes).
Change the base branch of the auto-generated Version Packages PR from master to develop and merge into develop.
Create a second PR to merge the develop branch into the master branch.

After merging the second PR into the master branch, packages will be automatically released to their respective locations according to the set of changeset files in the develop branch at the start of the process. Please carry this process out exactly as listed to avoid develop and master falling out of sync.

NOTE: PRs containing changeset files merged into develop during the release process can cause issues with changesets that can require manual intervention to fix. It's strongly recommended to avoid merging PRs into develop during an active release.

License

All other files within this repository are licensed under the MIT License unless stated otherwise.

AlexBHarley/op-stack-hooks