celo

README

Celo Blockchain

Official golang implementation of the Celo blockchain, based off of the official golang implementation of the Ethereum protocol.

Prebuilt Docker images are available for immediate use: us.gcr.io/celo-testnet/celo-node. See docs.celo.org/getting-started for a guide to the Celo networks and how to get started.

Documentation for Celo more generally can be found at docs.celo.org

Most functionality of this client is similar to go-ethereum, also known as geth, from which it was forked. If you do not find your question answered by Celo-specific documentation, try searching the geth wiki.

Building the source

Building geth requires both a Go (version 1.16) and a C compiler. You can install them using your favourite package manager. Once the dependencies are installed, run

make geth

or, to build the full suite of utilities:

make all

Mobile Clients

There are two different commands in the Makefile to build the ios and the android clients.

make ios

and

make android

Note: The android command it applies a git patch (patches/mobileLibsForBuild.patch) required to swap some libs from the go.mod for the client to work, installs those libs, builds the client, and then reverts the patch.

Executables

The Celo blockchain client comes with several wrappers/executables found in the cmd directory.

Command	Description
geth	The main Celo Blockchain client. It is the entry point into the Celo network, capable of running as a full node (default), archive node (retaining all historical state), light node (retrieving data live), or lightest node (retrieving minimum number of block headers to verify existing validator set). It can be used by other processes as a gateway into the Celo network via JSON RPC endpoints exposed on top of HTTP, WebSocket and/or IPC transports. geth --help and the Ethereum CLI Wiki page for command line options.
abigen	Source code generator to convert Celo contract definitions into easy to use, compile-time type-safe Go packages. It operates on plain Ethereum contract ABIs with expanded functionality if the contract bytecode is also available. However it also accepts Solidity source files, making development much more streamlined. Please see Ethereum's Native DApps wiki page for details.
bootnode	Stripped down version of the Celo client implementation that only takes part in the network node discovery protocol, but does not run any of the higher level application protocols. It can be used as a lightweight bootstrap node to aid in finding peers in private networks.
evm	Developer utility version of the EVM (Ethereum Virtual Machine) that is capable of running bytecode snippets within a configurable environment and execution mode. Its purpose is to allow isolated, fine-grained debugging of EVM opcodes (e.g. evm --code 60ff60ff --debug run).
gethrpctest	Developer utility tool to support the ethereum/rpc-test test suite which validates baseline conformity to the Ethereum JSON RPC specs. Please see the ethereum test suite's readme for details.
rlpdump	Developer utility tool to convert binary RLP (Recursive Length Prefix) dumps (data encoding used by the Celo protocol both network as well as consensus wise) to user friendlier hierarchical representation (e.g. rlpdump --hex CE0183FFFFFFC4C304050583616263).

Running tests

Prior to running tests you will need to run make prepare-system-contracts. This will checkout the celo-monorepo and compile the system contracts for use in full network tests. The rule will copy the compiled contracts from celo-monorepo to compiled-system-contracts. If you subsequently edit the system contracts source, running the make rule again will re-compile them and copy them into place.

This make rule will shallow checkout celo-monorepo under ../.celo-blockchain-monorepo-checkout relative to this project's root, and it will checkout the commit defined in the variable MONOREPO_COMMIT in the Makefile.

These values can be overridden if required, by setting those variables in the make command, for example:

make prepare-system-contracts MONOREPO_COMMIT=master MONOREPO_PATH=../alt-monorepo

Without first running this make rule, certain tests will fail with errors such as:

panic: Can't read bytecode for monorepo/packages/protocol/build/contracts/FixidityLib.json: open

Running Celo

Please see the docs.celo.org/getting-started for instructions on how to run a node connected the Celo network using the prebuilt Docker image.

Going through all the possible command line flags is out of scope here, please consult geth --help for more complete information. We've enumerated a few common parameter combos to get you up to speed quickly on how you can run your own Celo blockchain client instance.

Full node on the main Celo network

By default, the Celo client will connect to the Mainnet. Running the following command will create a full node that will sync with the Celo network and allow access to all of its functionality.

$ geth console

This command will:

• Start geth in full sync mode which will download and execute all historical block information.
• Start up geth's built-in interactive JavaScript console, (via the trailing console subcommand) through which you can invoke all official web3 methods as well as geth's own management APIs. This tool is optional and if you leave it out you can always attach to an already running geth instance with geth attach.

A Full node on the Alfajores test network

Smart contract developers will be most interested in the Alfajores testnet. On Alfajores, you can receive testnet Celo through the Alfajores faucet and deploy smart contracts in an environment very similar to Mainnet. More information about the Alfajores testnet can be found on docs.celo.org.

$ geth --alfajores console

Note: Although there are some internal protective measures to prevent transactions from crossing over between the main network and test network, you should make sure to always use separate accounts for testnet-tokens and real-tokens. Unless you manually move accounts, geth will by default correctly separate the two networks and will not make any accounts available between them.

Full node on the Baklava test network

Validators and full node operators will be most interested in the Baklava testnet. On Baklava, you can receive a distribution of testnet Celo Gold to become a validator on the network and test out running a validator for the first time, or try out new infrastructure. More information about the Baklava testnet can be found on docs.celo.org. A full guide to getting started as a validator on Baklava can be found in the Getting Started guides

$ geth --baklava console

Configuration

As an alternative to passing the numerous flags to the Celo binary, you can also pass a configuration file via:

$ geth --config /path/to/your_config.toml

To get an idea how the file should look like you can use the dumpconfig subcommand to export your existing configuration:

$ geth --your-favourite-flags dumpconfig

Programmatically interfacing geth nodes

As a developer, sooner rather than later you'll want to start interacting with geth and the Celo network via your own programs and not manually through the console. To aid this, geth has built-in support for a JSON-RPC based APIs (standard APIs and geth specific APIs). These can be exposed via HTTP, WebSockets and IPC (UNIX sockets on UNIX based platforms, and named pipes on Windows).

The IPC interface is enabled by default and exposes all the APIs supported by geth, whereas the HTTP and WS interfaces need to manually be enabled and only expose a subset of APIs due to security reasons. These can be turned on/off and configured as you'd expect.

HTTP based JSON-RPC API options:

• --http Enable the HTTP-RPC server
• --http.addr HTTP-RPC server listening interface (default: localhost)
• --http.port HTTP-RPC server listening port (default: 8545)
• --http.api API's offered over the HTTP-RPC interface (default: eth,net,web3)
• --http.corsdomain Comma separated list of domains from which to accept cross origin requests (browser enforced)
• --ws Enable the WS-RPC server
• --ws.addr WS-RPC server listening interface (default: localhost)
• --ws.port WS-RPC server listening port (default: 8546)
• --ws.api API's offered over the WS-RPC interface (default: eth,net,web3)
• --ws.origins value Origins from which to accept websockets requests
• --graphql Enable GraphQL on the HTTP-RPC server. Note that GraphQL can only be started if an HTTP server is started as well.
• --graphql.corsdomain value Comma separated list of domains from which to accept cross origin requests (browser enforced)
• --graphql.vhosts value Comma separated list of virtual hostnames from which to accept requests (server enforced). Accepts '*' wildcard. (default: "localhost")
• --ipcdisable Disable the IPC-RPC server
• --ipcapi API's offered over the IPC-RPC interface (default: admin,debug,eth,miner,net,personal,shh,txpool,web3)
• --ipcpath Filename for IPC socket/pipe within the datadir (explicit paths escape it)

You'll need to use your own programming environments' capabilities (libraries, tools, etc) to connect via HTTP, WS or IPC to a geth node configured with the above flags and you'll need to speak JSON-RPC on all transports. You can reuse the same connection for multiple requests!

Note: Please understand the security implications of opening up an HTTP/WS based transport before doing so! Hackers on the internet are actively trying to subvert Celo nodes with exposed APIs! Further, all browser tabs can access locally running web servers, so malicious web pages could try to subvert locally available APIs!

Contribution

Thank you for considering to help out with the source code! We welcome contributions from anyone on the internet, and are grateful for even the smallest of fixes!

If you'd like to contribute to celo-blockchain, please fork, fix, commit and send a pull request for the maintainers to review and merge into the main code base. If you wish to submit more complex changes though, please check up with the core devs first on the official Celo forum to ensure those changes are in line with the general philosophy of the project and/or get some early feedback which can make both your efforts much lighter as well as our review and merge procedures quick and simple.

Please make sure your contributions adhere to our coding guidelines:

• Code must adhere to the official Go formatting guidelines (i.e. uses gofmt).
• Code must be documented adhering to the official Go commentary guidelines.
• Pull requests need to be based on and opened against the master branch.
• Commit messages should be prefixed with the package(s) they modify.
  • E.g. "eth, rpc: make trace configs optional"

Submitting an issue

If you come across a bug, pleas open a GitHub issue with information about your build and what happened.

CI Testing and automerge

We run a circle CI test suite on each PR. The following tests are required to merge a PR.

• Unit tests: make test or ./build/env.sh go run build/ci.go test
• Lint: make lint (Fix go format errors with gofmt -s)
• Build: make
• End to end sync and transfer tests
• Check imports: ./scripts/check_imports.sh

celo-blockchain is based on go-ethereum, but the import path has been renamed from github.com/ethereum/go-ethereum to github.com/celo-org/celo-blockchain. Developers are encouraged to run ./scripts/setup_git_hooks.sh to enable checking that import path has been changed to celo-org on git merge and git commit. Imports can automatically be renamed with ./scripts/rename_imports.sh.

Individual package tests can be run with ./build/env.sh go test github.com/celo-org/celo-blockchain/$(PATH_TO_GO_PACKAGE) if you don't have GOPATH set-up.

Once a PR is approved, adding on the automerge label will keep it up to date and do a squash merge once all the required tests have passed.

Benchmarking

Golang has built in support for running benchmarks with go tool go test -run=ThisIsNotATestName -bench=. ./$PACKAGE_NAME will run all benchmarks in a package.

One note around running benchmarks is that BenchmarkHandlePreprepare is quite takes a while to run, particularly when testing with a larger number of validators. Substituting -bench=REGEX for -bench=. will specify which tests to run. Adding -cpuprofile=cpu.out which can be visualized with go tool pprof -html:8080 cpu.out if graphviz is installed.

See the go testing flags and go docs for more information on benchmarking.

License

The celo-blockchain library (i.e. all code outside of the cmd directory) is licensed under the GNU Lesser General Public License v3.0, also included in our repository in the COPYING.LESSER file.

The celo-blockchain binaries (i.e. all code inside of the cmd directory) is licensed under the GNU General Public License v3.0, also included in our repository in the COPYING file.

Documentation

Overview

Package celo defines interfaces for interacting with Celo.

Index

• Variables
• type CallMsg
• type ChainReader
• type ChainStateReader
• type ChainSyncReader
• type ContractCaller
• type FilterQuery
• type GasEstimator
• type GasPricer
• type LogFilterer
• type PendingContractCaller
• type PendingStateEventer
• type PendingStateReader
• type Subscription
• type SyncProgress
• type TransactionReader
• type TransactionSender

Variables

var NotFound = errors.New("not found")

NotFound is returned by API methods if the requested item does not exist.

Types

type CallMsg

type CallMsg struct {
	From                common.Address  // the sender of the 'transaction'
	To                  *common.Address // the destination contract (nil for contract creation)
	Gas                 uint64          // if 0, the call executes with near-infinite gas
	FeeCurrency         *common.Address // 0 for the native currency
	GatewayFeeRecipient *common.Address // 0 for no gateway fee
	GatewayFee          *big.Int        // 0 for no gateway fee
	GasPrice            *big.Int        // wei <-> gas exchange ratio
	GasFeeCap           *big.Int        // EIP-1559 fee cap per gas.
	GasTipCap           *big.Int        // EIP-1559 tip per gas.
	Value               *big.Int        // amount of wei sent along with the call
	Data                []byte          // input data, usually an ABI-encoded contract method invocation
	EthCompatible       bool            // Whether the 3 Celo-only fields (FeeCurrency & co.) were omitted

	AccessList types.AccessList // EIP-2930 access list.
}

CallMsg contains parameters for contract calls.

type ChainReader

type ChainReader interface {
	BlockByHash(ctx context.Context, hash common.Hash) (*types.Block, error)
	BlockByNumber(ctx context.Context, number *big.Int) (*types.Block, error)
	HeaderByHash(ctx context.Context, hash common.Hash) (*types.Header, error)
	HeaderByNumber(ctx context.Context, number *big.Int) (*types.Header, error)
	TransactionCount(ctx context.Context, blockHash common.Hash) (uint, error)
	TransactionInBlock(ctx context.Context, blockHash common.Hash, index uint) (*types.Transaction, error)

	// This method subscribes to notifications about changes of the head block of
	// the canonical chain.
	SubscribeNewHead(ctx context.Context, ch chan<- *types.Header) (Subscription, error)
}

ChainReader provides access to the blockchain. The methods in this interface access raw data from either the canonical chain (when requesting by block number) or any blockchain fork that was previously downloaded and processed by the node. The block number argument can be nil to select the latest canonical block. Reading block headers should be preferred over full blocks whenever possible.

The returned error is NotFound if the requested item does not exist.

type ChainStateReader

type ChainStateReader interface {
	BalanceAt(ctx context.Context, account common.Address, blockNumber *big.Int) (*big.Int, error)
	StorageAt(ctx context.Context, account common.Address, key common.Hash, blockNumber *big.Int) ([]byte, error)
	CodeAt(ctx context.Context, account common.Address, blockNumber *big.Int) ([]byte, error)
	NonceAt(ctx context.Context, account common.Address, blockNumber *big.Int) (uint64, error)
}

ChainStateReader wraps access to the state trie of the canonical blockchain. Note that implementations of the interface may be unable to return state values for old blocks. In many cases, using CallContract can be preferable to reading raw contract storage.

type ChainSyncReader

type ChainSyncReader interface {
	SyncProgress(ctx context.Context) (*SyncProgress, error)
}

ChainSyncReader wraps access to the node's current sync status. If there's no sync currently running, it returns nil.

type ContractCaller

type ContractCaller interface {
	CallContract(ctx context.Context, call CallMsg, blockNumber *big.Int) ([]byte, error)
}

A ContractCaller provides contract calls, essentially transactions that are executed by the EVM but not mined into the blockchain. ContractCall is a low-level method to execute such calls. For applications which are structured around specific contracts, the abigen tool provides a nicer, properly typed way to perform calls.

type FilterQuery

type FilterQuery struct {
	BlockHash *common.Hash     // used by eth_getLogs, return logs only from block with this hash
	FromBlock *big.Int         // beginning of the queried range, nil means genesis block
	ToBlock   *big.Int         // end of the range, nil means latest block
	Addresses []common.Address // restricts matches to events created by specific contracts

	// The Topic list restricts matches to particular event topics. Each event has a list
	// of topics. Topics matches a prefix of that list. An empty element slice matches any
	// topic. Non-empty elements represent an alternative that matches any of the
	// contained topics.
	//
	// Examples:
	// {} or nil          matches any topic list
	// {{A}}              matches topic A in first position
	// {{}, {B}}          matches any topic in first position AND B in second position
	// {{A}, {B}}         matches topic A in first position AND B in second position
	// {{A, B}, {C, D}}   matches topic (A OR B) in first position AND (C OR D) in second position
	Topics [][]common.Hash
}

FilterQuery contains options for contract log filtering.

type GasEstimator

type GasEstimator interface {
	EstimateGas(ctx context.Context, call CallMsg) (uint64, error)
}

GasEstimator wraps EstimateGas, which tries to estimate the gas needed to execute a specific transaction based on the pending state. There is no guarantee that this is the true gas limit requirement as other transactions may be added or removed by miners, but it should provide a basis for setting a reasonable default.

type GasPricer

type GasPricer interface {
	SuggestGasPrice(ctx context.Context) (*big.Int, error)
}

GasPricer wraps the gas price oracle, which monitors the blockchain to determine the optimal gas price given current fee market conditions.

type LogFilterer

type LogFilterer interface {
	FilterLogs(ctx context.Context, q FilterQuery) ([]types.Log, error)
	SubscribeFilterLogs(ctx context.Context, q FilterQuery, ch chan<- types.Log) (Subscription, error)
}

LogFilterer provides access to contract log events using a one-off query or continuous event subscription.

Logs received through a streaming query subscription may have Removed set to true, indicating that the log was reverted due to a chain reorganisation.

type PendingContractCaller

type PendingContractCaller interface {
	PendingCallContract(ctx context.Context, call CallMsg) ([]byte, error)
}

PendingContractCaller can be used to perform calls against the pending state.

type PendingStateEventer

type PendingStateEventer interface {
	SubscribePendingTransactions(ctx context.Context, ch chan<- *types.Transaction) (Subscription, error)
}

A PendingStateEventer provides access to real time notifications about changes to the pending state.

type PendingStateReader

type PendingStateReader interface {
	PendingBalanceAt(ctx context.Context, account common.Address) (*big.Int, error)
	PendingStorageAt(ctx context.Context, account common.Address, key common.Hash) ([]byte, error)
	PendingCodeAt(ctx context.Context, account common.Address) ([]byte, error)
	PendingNonceAt(ctx context.Context, account common.Address) (uint64, error)
	PendingTransactionCount(ctx context.Context) (uint, error)
}

A PendingStateReader provides access to the pending state, which is the result of all known executable transactions which have not yet been included in the blockchain. It is commonly used to display the result of ’unconfirmed’ actions (e.g. wallet value transfers) initiated by the user. The PendingNonceAt operation is a good way to retrieve the next available transaction nonce for a specific account.

type Subscription

type Subscription interface {
	// Unsubscribe cancels the sending of events to the data channel
	// and closes the error channel.
	Unsubscribe()
	// Err returns the subscription error channel. The error channel receives
	// a value if there is an issue with the subscription (e.g. the network connection
	// delivering the events has been closed). Only one value will ever be sent.
	// The error channel is closed by Unsubscribe.
	Err() <-chan error
}

Subscription represents an event subscription where events are delivered on a data channel.

type SyncProgress

type SyncProgress struct {
	StartingBlock uint64 // Block number where sync began
	CurrentBlock  uint64 // Current block number where sync is at
	HighestBlock  uint64 // Highest alleged block number in the chain
	PulledStates  uint64 // Number of state trie entries already downloaded
	KnownStates   uint64 // Total number of state trie entries known about
}

SyncProgress gives progress indications when the node is synchronising with the Ethereum network.

type TransactionReader

type TransactionReader interface {
	// TransactionByHash checks the pool of pending transactions in addition to the
	// blockchain. The isPending return value indicates whether the transaction has been
	// mined yet. Note that the transaction may not be part of the canonical chain even if
	// it's not pending.
	TransactionByHash(ctx context.Context, txHash common.Hash) (tx *types.Transaction, isPending bool, err error)
	// TransactionReceipt returns the receipt of a mined transaction. Note that the
	// transaction may not be included in the current canonical chain even if a receipt
	// exists.
	TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error)
}

TransactionReader provides access to past transactions and their receipts. Implementations may impose arbitrary restrictions on the transactions and receipts that can be retrieved. Historic transactions may not be available.

Avoid relying on this interface if possible. Contract logs (through the LogFilterer interface) are more reliable and usually safer in the presence of chain reorganisations.

The returned error is NotFound if the requested item does not exist.

type TransactionSender

type TransactionSender interface {
	SendTransaction(ctx context.Context, tx *types.Transaction) error
}

TransactionSender wraps transaction sending. The SendTransaction method injects a signed transaction into the pending transaction pool for execution. If the transaction was a contract creation, the TransactionReceipt method can be used to retrieve the contract address after the transaction has been mined.

The transaction must be signed and have a valid nonce to be included. Consumers of the API can use package accounts to maintain local private keys and need can retrieve the next available nonce using PendingNonceAt.