What is eth-block-tracker?
The eth-block-tracker npm package is designed to help developers track the latest blocks on the Ethereum blockchain. It provides a simple interface to subscribe to new block events, poll for new blocks, and manage block tracking efficiently.
What are eth-block-tracker's main functionalities?
Polling for New Blocks
This feature allows you to poll for new blocks on the Ethereum blockchain. The code sample demonstrates how to set up a block tracker that listens for the latest block and logs it to the console.
const EthBlockTracker = require('eth-block-tracker');
const provider = require('eth-provider');
const blockTracker = new EthBlockTracker({ provider: provider() });
blockTracker.on('latest', (block) => {
console.log('Latest block:', block);
});
blockTracker.start();
Handling Errors
This feature allows you to handle errors that may occur during block tracking. The code sample demonstrates how to set up an error handler that logs errors to the console.
const EthBlockTracker = require('eth-block-tracker');
const provider = require('eth-provider');
const blockTracker = new EthBlockTracker({ provider: provider() });
blockTracker.on('error', (error) => {
console.error('Error:', error);
});
blockTracker.start();
Custom Polling Interval
This feature allows you to set a custom polling interval for checking new blocks. The code sample demonstrates how to set up a block tracker with a polling interval of 20 seconds.
const EthBlockTracker = require('eth-block-tracker');
const provider = require('eth-provider');
const blockTracker = new EthBlockTracker({ provider: provider(), pollingInterval: 20000 });
blockTracker.on('latest', (block) => {
console.log('Latest block:', block);
});
blockTracker.start();
Other packages similar to eth-block-tracker
web3
The web3 package is a comprehensive library for interacting with the Ethereum blockchain. It includes functionality for tracking blocks, but also provides a wide range of other features such as contract interaction, account management, and more. Compared to eth-block-tracker, web3 is more feature-rich but may be overkill if you only need block tracking.
ethers
The ethers package is another popular library for interacting with the Ethereum blockchain. It offers similar functionalities to web3, including block tracking, but is known for its smaller size and better performance. Like web3, it provides a broader set of features beyond block tracking.
ethereumjs-blockstream
The ethereumjs-blockstream package is specifically designed for streaming Ethereum blocks. It provides a more focused approach to block tracking compared to web3 and ethers, making it a closer alternative to eth-block-tracker. However, it may not be as widely used or supported as the other two libraries.
eth-block-tracker
This module walks the Ethereum blockchain, keeping track of the latest block. It uses a web3 provider as a data source and will continuously poll for the next block.
Installation
yarn add eth-block-tracker
or
npm install eth-block-tracker
Usage
const createInfuraProvider = require('eth-json-rpc-infura');
const { PollingBlockTracker } = require('eth-block-tracker');
const provider = createInfuraProvider({
network: 'mainnet',
projectId: process.env.INFURA_PROJECT_ID,
});
const blockTracker = new PollingBlockTracker({ provider });
blockTracker.on('sync', ({ newBlock, oldBlock }) => {
if (oldBlock) {
console.log(`sync #${Number(oldBlock)} -> #${Number(newBlock)}`);
} else {
console.log(`first sync #${Number(newBlock)}`);
}
});
API
Methods
new PollingBlockTracker({ provider, pollingInterval, retryTimeout, keepEventLoopActive, usePastBlocks })
- Creates a new block tracker with
provider
as a data source and pollingInterval
(ms) timeout between polling for the latest block. - If an error is encountered when fetching blocks, it will wait
retryTimeout
(ms) before attempting again. - If
keepEventLoopActive
is false
, in Node.js it will unref the polling timeout, allowing the process to exit during the polling interval. Defaults to true
, meaning the process will be kept alive. - If
usePastBlocks
is true
, block numbers less than the current block number can used and emitted. Defaults to false
, meaning that only block numbers greater than the current block number will be used and emitted.
getCurrentBlock()
Synchronously returns the current block. May be null
.
console.log(blockTracker.getCurrentBlock());
async getLatestBlock()
Asynchronously returns the latest block. if not immediately available, it will fetch one.
async checkForLatestBlock()
Tells the block tracker to ask for a new block immediately, in addition to its normal polling interval. Useful if you received a hint of a new block (e.g. via tx.blockNumber
from getTransactionByHash
). Will resolve to the new latest block when done polling.
Events
latest
The latest
event is emitted for whenever a new latest block is detected. This may mean skipping blocks if there were two created since the last polling period.
blockTracker.on('latest', (newBlock) => console.log(newBlock));
sync
The sync
event is emitted the same as "latest" but includes the previous block.
blockTracker.on('sync', ({ newBlock, oldBlock }) =>
console.log(newBlock, oldBlock),
);
error
The error
event means an error occurred while polling for the latest block.
blockTracker.on('error', (err) => console.error(err));
Contributing
Setup
- Install Node.js version 16 or greater
- If you are using nvm (recommended) running
nvm use
will automatically choose the right node version for you.
- Install Yarn v1
- Run
yarn setup
to install dependencies and run any requried post-install scripts
- Warning: Do not use the
yarn
/ yarn install
command directly. Use yarn setup
instead. The normal install command will skip required post-install scripts, leaving your development environment in an invalid state.
Testing and Linting
Run yarn test
to run the tests once. To run tests on file changes, run yarn test:watch
.
Run yarn lint
to run the linter, or run yarn lint:fix
to run the linter and fix any automatically fixable issues.
Release & Publishing
The project follows the same release process as the other libraries in the MetaMask organization. The GitHub Actions action-create-release-pr
and action-publish-release
are used to automate the release process; see those repositories for more information about how they work.
-
Choose a release version.
- The release version should be chosen according to SemVer. Analyze the changes to see whether they include any breaking changes, new features, or deprecations, then choose the appropriate SemVer version. See the SemVer specification for more information.
-
If this release is backporting changes onto a previous release, then ensure there is a major version branch for that version (e.g. 1.x
for a v1
backport release).
- The major version branch should be set to the most recent release with that major version. For example, when backporting a
v1.0.2
release, you'd want to ensure there was a 1.x
branch that was set to the v1.0.1
tag.
-
Trigger the workflow_dispatch
event manually for the Create Release Pull Request
action to create the release PR.
- For a backport release, the base branch should be the major version branch that you ensured existed in step 2. For a normal release, the base branch should be the main branch for that repository (which should be the default value).
- This should trigger the
action-create-release-pr
workflow to create the release PR.
-
Update the changelog to move each change entry into the appropriate change category (See here for the full list of change categories, and the correct ordering), and edit them to be more easily understood by users of the package.
- Generally any changes that don't affect consumers of the package (e.g. lockfile changes or development environment changes) are omitted. Exceptions may be made for changes that might be of interest despite not having an effect upon the published package (e.g. major test improvements, security improvements, improved documentation, etc.).
- Try to explain each change in terms that users of the package would understand (e.g. avoid referencing internal variables/concepts).
- Consolidate related changes into one change entry if it makes it easier to explain.
- Run
yarn auto-changelog validate --rc
to check that the changelog is correctly formatted.
-
Review and QA the release.
- If changes are made to the base branch, the release branch will need to be updated with these changes and review/QA will need to restart again. As such, it's probably best to avoid merging other PRs into the base branch while review is underway.
-
Squash & Merge the release.
- This should trigger the
action-publish-release
workflow to tag the final release commit and publish the release on GitHub.
-
Publish the release on npm.
- Be very careful to use a clean local environment to publish the release, and follow exactly the same steps used during CI.
- Use
npm publish --dry-run
to examine the release contents to ensure the correct files are included. Compare to previous releases if necessary (e.g. using https://unpkg.com/browse/[package name]@[package version]/
). - Once you are confident the release contents are correct, publish the release using
npm publish
.