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Earthstar

User Guide

Earthstar is a small and resilient distributed storage protocol designed with a strong focus on simplicity and versatility, with the social realities of peer-to-peer computing kept in mind.

This is a reference implementation written in Typescript. You can use it to add Earthstar functionality to applications running on servers, browsers, the command line, or anywhere else JavaScript can be run.

Detailed API documentation for this module can be found here.

This document is concerned with the usage of this module's APIs. To learn more about what Earthstar is, please see these links:

To learn more about running Earthstar servers, see README_SERVERS

To learn more about this codebase, please see ARCHITECTURE.

To learn about contributing to this codebase, please see CONTRIBUTING.

Table of contents

Importing the module

It can be imported via URL into a browser:

<script type="module">
  import * as Earthstar from "https://cdn.earthstar-project.org/js/earthstar.web.v10.0.1.js";
</script>

Or Deno:

import * as Earthstar from "https://deno.land/x/earthstar/mod.ts";`}

Earthstar's web syncing does not work with version of Deno between 1.27.0 - 1.29.3 (inclusive) due to a regression in these versions' WebSocket implementation. Use Deno 1.30.0. or later, or Deno 1.26.2.

or installed with NPM:

{`npm install earthstar`}

We recommend the browser and Deno versions. This module has been built with many standard web APIs that have need to be polyfilled to work in Node.

Instantiating a replica

Replica is the central API of this module. It is used to write and read data to a locally persisted copy of a share's data, and much more besides.

To instantiate a replica, you will need knowledge of a share's public address.

import { Replica, ReplicaDriverMemory } from "earthstar";

const replica = new Replica({
  driver: ReplicaDriverMemory(YOUR_SHARE_ADDRESS),
  shareSecret: YOUR_SHARE_SECRET,
});

The shareSecret property is optional. If we omit it, the replica will be read-only.

Generating share keypairs

You can create new shares whenever you want.

import { Crypto } from "earthstar";

const shareKeypair = await Crypto.generateShareKeypair("gardening");

The result of this operation will either be a ShareKeypair object with shareAddress and secret properties, or a ValidationError.

Persisting data with drivers

Replica must always be instantiated with a driver. These drivers tell the Replica how to store and retrieve data, with different drivers using different storage mechanisms.

Here are the available drivers:

Drivers are made of two sub-drivers: one for documents, and one for attachments (arbitrary binary data).

There are some extra document drivers not used in the default drivers:

These document drivers can be used like this:

const driver: IReplicaDriver = {
  docDriver: new DocDriverSqliteFfi(SHARE_ADDR, FS_PATH),
  attachmentDriver: new AttachmentDriverFs(FS_ATTACHMENTS_PATH),
};

const replica = new Replica({ driver });

Writing data

Writing data requires two things:

Author keypairs can be generated like this:

import { Crypto } from "earthstar";

const authorKeypair = await Crypto.generateAuthorKeypair("suzy");

The result will be a new AuthorKeypair object with address and secret properties, or a ValidationError.

With a valid author keypair you can write data using Replica.set:

const setResult = await replica.set(authorKeypair, {
  path: "/my-note",
  text: "Saw seven magpies today",
});

The result of this operation is either an IngestEvent describing the operation's success (or failure, if one of the parameters was invalid in some way).

Wiping data

Once written, data can be removed by overwriting it:

await replica.set(authorKeypair, {
  path: "/my-note",
  text: "",
});

Or with the convenience method:

await replica.wipeDocAtPath(authorKeypair, "/my-note");

Creating ephemeral documents

There is another way to remove written data without leaving any trace of it.

Ephemeral documents are held by replicas until a specified time, until at which point they are deleted.

await replica.set(authorKeypair, {
  path: "/my-temporary-note!",
  text: "I accidentally stepped on the strawberries.",
  deleteAfter: TIME_IN_MICROSECONDS,
});

To set an ephemeral document, the path must contain a !, and the deleteAfter property must be set with a timestamp in microseconds.

Querying data

There are many ways to get data back out of a Replica. The simplest one is Replica.getAllDocs:

const everything = await replica.getAllDocs();

The most powerful is Replica.queryDocs:

const mostRecentlyEditedWikiPageDocs = await replica.queryDocs({
  historyMode: "latest",
  filter: {
    pathStartsWith: "/wiki",
  },
  limit: 10,
});

Here are all the querying methods on Replica:

Detailed API documentation for all of them can be found here.

Using document contents

The documents returned by queries are plain objects with the following shape:

type Doc = {
  /** Which document format the doc adheres to, e.g. `es.5`. */
  format: "es.5";
  author: AuthorAddress;
  text: string;
  textHash: string;
  /** When the document should be deleted, as a UNIX timestamp in microseconds. */
  deleteAfter?: number;
  path: Path;
  /** Used to verify the authorship of the document. */
  signature: Signature;
  /** Used to verify the author knows the share's secret */
  shareSignature: Signature;
  /** When the document was written, as a UNIX timestamp in microseconds (millionths of a second, e.g. `Date.now() * 1000`).*/
  timestamp: Timestamp;
  /** The share this document is from. */
  share: ShareAddress;
  /** The size of the associated attachment in bytes, if any. */
  attachmentSize?: number;
  /** The sha256 hash of the associated attachment, if any. */
  attachmentHash?: string;
};

Though most applications will probably only use the author, text, and timestamp properties.

Syncing with other peers

Syncing data with other peers requires adding your replica(s) to an instance of Peer:

import { Peer } from "earthstar";

const peer = new Peer();

// Pretend myReplica is an instance of `Replica`
peer.addReplica(myReplica);

peer.sync("https://my.server");

Peer.sync can be passed another instance of Peer or a valid URL of an Earthstar server to sync with.

The two peers will only sync the replicas with shares they have in common.

The result of Peer.sync can be assigned and used to monitor the progress of the sync operation:

const syncer = peer.sync("https://my.server");

syncer.onStatusChange((newStatus) => {
  console.log(newStatus);
});

syncer.isDone().then(() => {
  console.log("Sync complete");
}).catch((err) => {
  console.error("Sync failed", err);
});

Using document attachments

Documents can be written along with some arbitrary data which is persisted as an 'attachment'. Whereas a document's text field can hold a UTF-8 string of 8kb, attachments can be of any kind of data and of any size.

// Here we use Deno.readFile to get a file's contents as a Uint8Array
const imageData = await Deno.readFile("/Desktop/leaf.jpg");

await replica.set(authorKeypair, {
  path: "/images/pear-leaf.jpg",
  text: "A close-up of a leaf of a pear tree",
  attachment: imageData,
});

The path must have a file extension e.g. .jpg, .mp3 if it also has an attachment.

If we were attaching a large amount of data, we would use a ReadableStream instead:

// Here we use Deno.readFile to get a file's contents as a ReadableStream<Uint8Array>
const videoFile = await Deno.open("/Desktop/little-mole.mp4");

await replica.set(authorKeypair, {
  path: "/videos/little-mole.mp4",
  text: "A close-up of a leaf of a pear tree",
  attachment: videoFile.readable,
});

Retrieving attachments

If you already have a document with an attachment, you can use Replica.getAttachment:

const attachment = await replica.getAttachment(docWithAttachment);

The result of this operation will be a DocAttachment with getBytes and getStream methods, undefined (if our replica has not received a copy of this attachment from other peers), or a ValidationError in case getAttachment was passed a document which can't have an attachment.

It's also possible to add attachments to many documents at once:

const allDocs = await replica.getAllDocs();

const allDocsWithAttachments = await replica.addAttachments(allDocs);

allDocsWithAttachments will be an array of all documents with an added attachment property. The type of this property will either be DocAttachment, undefined, or ValidationError.

Subscribing to replica changes

There are many ways to subscribe to the many events a replica generates during its lifetime.

If you want to subscribe to updates in order to update a UI, the most ergonomic API is ReplicaCache:

import { ReplicaCache } from "earthstar";

const replicaCache = new ReplicaCache(myReplica);

const allDocs = replicaCache.getAllDocs();

The caveat is that the first time a query method is called, it always returns an empty result. To get new updates, you must subscribe to changes. In the following example, we build a UI with a fictitious renderDocListUI function with the results of ReplicaCache.getAllDocs:

function triggerUIRender() {
  const allDocs = replicaCache.getAllDocs();

  renderDocListUI(allDocs);
}

replicaCache.onCacheUpdated(() => {
  triggerUIRender();
});

triggerUIRender();

The important thing to remember is that the callback to onCacheUpdated will never trigger until the cache has been queried at least once.

If you're not tracking changes for a UI, Replica.getQueryStream returns a ReadableStream of QuerySourceEvent, for documents matching a specific query. This API is great for creating indexes.

// Create a query stream for all docs with paths starting with /chat
// And include all existing documents and all newly created or synced documents
const chatMessagesStream = replica.getQueryStream({
  filter: { pathStartsWith: "/chat" },
}, "everything");

chatMessagesStream.pipeTo(
  new WritableStream({
    write(event) {
      if (event.kind === "success" || event.kind === "existing") {
        console.log(event.doc.text);
      }
    },
  }),
);

Finally, Replica.getEventStream returns a ReadableStream of ReplicaEvent, which includes events for new document ingestions, document expirations, attachment ingestions, attachment prunes, and events for when the replica is about to close (and has closed).

Using common settings between clients

There are a number of configurations which most Earthstar applications will want to persist between runs:

Earthstar offers a SharedSettings API which persists settings for these between sessions in all runtimes supporting the WebStorage APIs:

const settings = new SharedSettings();

settings.author = authorKeypair;
settings.addShare(myShareAddress);
console.log(settings.servers);

It also offers a method which instantiates a new Peer with replicas for all shares already added:

const settings = new SharedSettings();

// Create a peer with all saved shares and sync once with all saved servers.
const peer = settings.getPeer({
  sync: "once",
  onCreateReplica: (addr, secret) => {
    return new Replica({
      driver: new ReplicaDriverMemory(addr),
      shareSecret: secret,
    });
  },
});

Checking for errors

Many functions in Earthstar return errors like ValidationError. These errors are not thrown, so it's good to check for them:

import { isErr } from "earthstar";

const result = replica.set(authorKeypair, {
  path: "/hey",
  text: "Hello",
});

if (isErr(result)) {
  console.error(
    "Something went wrong when you tried to write some data!",
    result,
  );
}

Changing the cryptographic driver

The Deno and browser versions of this module are configured by default to use the fastest cryptographic libraries available to them. The Node version is not, however.

import { setGlobalCryptoDriver } from "earthstar";
import { CryptoDriverChloride } from "earthstar/node";

setGlobalCryptoDriver(CryptoDriverChloride);