geteventstore-promise

A Node.js Event Store client API wrapper using promises

Installation

yarn add geteventstore-promise

In your Node.js application:

const EventStore = require('geteventstore-promise');

HTTP Client

Config example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

Config example - Secure

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	protocol: 'https',
	hostname: 'localhost',
	port: 2113,
	validateServer: true, //defaults to `true` when `protocol` is `https`, set to `false` when using self-signed certs
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

Supported Methods

getEvents(streamName, startPosition, count, direction, resolveLinkTos, embed)

Returns events from a given stream.

streamName

The name of the stream to read from.

startPosition (optional)

If specified, the stream will be read starting at event number startPosition, otherwise 0 'head' will start reading from the back of the stream, if direction is specified as 'backward'

count (optional)

The number of events to be read, defaults to 1000, max of 4096

direction (optional)

The direction to the read the stream. Can be either 'forward' or 'backward'. Defaults to 'forward'.

resolveLinkTos (optional)

Resolve linked events. Defaults to true

embed (optional)

Resolve linked events. Options: 'body' and 'rich'. Defaults to body

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

// defaults for getEvents if not specified
const events = await client.getEvents('TestStream', 0, 1000, 'forward')

---

getAllStreamEvents(streamName, chunkSize, startPosition, resolveLinkTos, embed)

Returns all events from a given stream.

streamName

The name of the stream to read from.

chunkSize (optional)

The amount of events to read in each call to Event Store, defaults to 1000,

startPosition (optional)

If specified, the stream will be read starting at event number startPosition, otherwise 0

resolveLinkTos (optional)

Resolve linked events. Defaults to true

embed (optional)

Resolve linked events. Options: 'body' and 'rich'. Defaults to body

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

const allStreamEvents = await client.getAllStreamEvents('TestStream');

readEventsForward(streamName, startPosition, count, resolveLinkTos, embed)

Returns read metadata and events from a given stream.

streamName

The name of the stream to read from.

startPosition (optional)

If specified, the stream will be read starting at event number startPosition, otherwise 0 'head' will start reading from the back of the stream, if direction is specified as 'backward'

count (optional)

The number of events to be read, defaults to 1000, max of 4096

resolveLinkTos (optional)

Resolve linked events. Defaults to true

embed (optional)

Resolve linked events. Options: 'body' and 'rich'. Defaults to body

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

// defaults for readEventsForward if not specified
const readResult = await client.readEventsForward('TestStream', 0, 1000)

readEventsBackward(streamName, startPosition, count, resolveLinkTos, embed)

Returns read metadata and events from a given stream.

streamName

The name of the stream to read from.

startPosition (optional)

If specified, the stream will be read starting at event number startPosition, otherwise 0 'head' will start reading from the back of the stream, if direction is specified as 'backward'

count (optional)

The number of events to be read, defaults to 1000, max of 4096

resolveLinkTos (optional)

Resolve linked events. Defaults to true

embed (optional)

Resolve linked events. Options: 'body' and 'rich'. Defaults to body

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

// defaults for readEventsBackward if not specified
const readResult = await client.readEventsBackward('TestStream', 0, 1000)

---

writeEvent(streamName, eventType, data, metaData, options)

Writes a single event of a specific type to a stream.

streamName

The name of the stream to read from.

eventType

The type of event to save. Any string value is accepted.

data

The data to be contained in the event as a JSON object.

metaData (optional)

Any MetaData to be saved in the event as a JSON object.

options (optional)

Any options to be specified (as documented in GetEvent Store documentation). Default is simply ExpectedVersion = -2.

Example

const EventStore = require('geteventstore-promise');
const { v4: generateEventId } = require('uuid');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

await client.writeEvent('TestStream-' + generateEventId(), 'TestEventType', { something: '123' });
const events = await client.getEvents(testStream);

---

writeEvents(streamName, events, options)

Writes an array of Event Store ready events to a stream.

streamName

The name of the stream to read from.

events

The array of Event Store ready events to save. You can call new EventStore.EventFactory().newEvent('TestType', {something: 123}); to get an Event Store ready event.

options (optional)

Any options to be specified (as documented in GetEvent Store documentation). Default is simply ExpectedVersion = -2.

Example

const EventStore = require('geteventstore-promise');
const { v4: generateEventId } = require('uuid');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

const events = [new EventStore.EventFactory().newEvent('TestEventType', { something: '456'})];

await client.writeEvents('TestStream-' + generateEventId(), events);
const events = await client.getEvents(testStream);

---

checkStreamExists(streamName)

Check if a stream exists, returns true or false.

streamName

The name of the stream to check.

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

const exists = await client.checkStreamExists('ExistingProjectionStreamName');

---

deleteStream(streamName, hardDelete)

Deletes a stream, fails the promise if stream does not exist.

streamName

The name of the stream to delete.

hardDelete

Hard delete the stream, defaults to false

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

try {
	await client.delete('ExistingStreamName');
} catch(err) {
	// should only happen if something went wrong or the stream does not exist
    console.log(err);
}

---

ping()

Performs Ping command, rejects promise if unsuccessful

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

await client.ping();

---

Persistent Subscriptions

Supported Methods

• assert(subscriptionName, streamName, options)
• getEvents(subscriptionName, streamName, count, embed)
• getSubscriptionInfo(subscriptionName, streamName)
• getStreamSubscriptionsInfo(streamName)
• getAllSubscriptionsInfo()
• remove(subscriptionName, streamName)

persistentSubscriptions.assert(subscriptionName, streamName, options)

Upsert the persistent subscription

subscriptionName

The name of the subscription group

streamName

The stream name

options(optional)

The mode of the projection to create, defaults to 'continuous'

resolveLinkTos

Tells the subscription to resolve link events.

startFrom

Start the subscription from the position-th event in the stream.

extraStatistics

Tells the backend to measure timings on the clients so statistics will contain histograms of them.

checkPointAfterMilliseconds

The amount of time the system should try to checkpoint after.

liveBufferSize

The size of the live buffer (in memory) before resorting to paging.

readBatchSize

The size of the read batch when in paging mode.

bufferSize

The number of messages that should be buffered when in paging mode.

maxCheckPointCount

The maximum number of messages not checkpointed before forcing a checkpoint.

maxRetryCount

Sets the number of times a message should be retried before being considered a bad message.

maxSubscriberCount

Sets the maximum number of allowed subscribers

messageTimeoutMilliseconds

Sets the timeout for a client before the message will be retried.

minCheckPointCount

The minimum number of messages to write a checkpoint for.

namedConsumerStrategy

RoundRobin/DispatchToSingle/Pinned

persistentSubscriptions.getEvents(subscriptionName, streamName, count, embed)

Get events

subscriptionName

The name of the subscription group

streamName

The stream name

count (optional)

Number of events to return(defaults to 1)

embed (optional)

None, Content, Rich, Body, PrettyBody, TryHarder(defaults to 'Body')

persistentSubscriptions.getSubscriptionInfo(subscriptionName, streamName)

Get specific subscriptions info

subscriptionName

The name of the subscription group

streamName

The stream name

persistentSubscriptions.getStreamSubscriptionsInfo(streamName)

Get all subscriptions info for a stream

streamName

The stream name

persistentSubscriptions.getAllSubscriptionsInfo()

Get all subscriptions info

---

Projections

Supported Methods

• start(projectionName)

  projectionName

  The name of the projection

• stop(projectionName)

  projectionName

  The name of the projection

• reset(projectionName)

  projectionName

  The name of the projection

• remove(projectionName)

  projectionName

  The name of the projection

• config(projectionName)

  projectionName

  The name of the projection

• getState(projectionName, options)

  projectionName

  The name of the projection

  options

  Object, partition used to specify the partition to query the state with. e.g. { partition: 1 }

• getInfo(projectionName, includeConfig)

  projectionName

  The name of the projection

  includeConfig

  Specify if we want to include the projection config in the projection info result set

• enableAll()

• disableAll()

• getAllProjectionsInfo()

• assert(projectionName, projectionContent, mode, enabled, checkpointsEnabled, emitEnabled, trackEmittedStreams)

  projectionName

  The name of the projection

  projectionContent

  The content of the projection

  mode(optional)

  The mode of the projection to create, defaults to 'continuous'

  enabled(optional)

  Projection enabled by default, defaults to true

  checkpointsEnabled(optional)

  Should enable checkpoints, defaults to true for continuous projections and false for onetime projections

  emitEnabled(optional)

  Should enable emitting, defaults to false

  trackEmittedStreams(optional)

  Should track the emitted streams (tracking emitted streams enables you to delete a projection and all the streams that it has created), defaults to false

Example for using any projection method

projections.getState()

Returns the state of the Projection as a JSON object.

projectionName

The name of the projection to get state of.

options(optional)

partition

The name of the partition to retrieve.

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

const projectionState = await client.projections.getState('TestProjection');

---

Admin

admin.scavenge()

Sends scavenge command to Event Store.

If the promise is fulfilled then the scavenge command has been sent, it does not guarantee that the scavenge will be successful.

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

await client.admin.scavenge();
console.log('Scavenge command sent!');

---

admin.shutdown()

Sends shutdown command to Event Store.

If the promise is fulfilled then the shutdown command has been sent, it does not guarantee that the shutdown will be successful.

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.HTTPClient({
	hostname: 'localhost',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

await client.admin.shutdown();
console.log('Shutdown command sent!');

---

TCP Client

Acknowledgements

Uses the node-eventstore-client as authored by nicdex

Github: https://github.com/nicdex/node-eventstore-client

Config example

const client = new EventStore.TCPClient({
	hostname: 'localhost',
	port: 1113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	},
	poolOptions: {
		min: 0,
		max: 10
	}
});

Config example - Secure

const client = new EventStore.TCPClient({
	hostname: 'localhost',
	port: 1113,
	useSslConnection: true,
	validateServer: true, //defaults to `true` when `useSslConnection` is `true`, set to `false` when using self-signed certs
	credentials: {
		username: 'admin',
		password: 'changeit'
	},
	poolOptions: {
		min: 0,
		max: 10
	}
});

Config example - Override connection name

const { v4: generateId } = require('uuid');

const client = new EventStore.TCPClient({
	hostname: 'localhost',
	port: 1113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	},
	poolOptions: {
		min: 0,
		max: 10
	},
	connectionNameGenerator: () => `APP_NAME_${generateId()}`
});

Config example - Clustering - Gossip Seeds

const client = new EventStore.TCPClient({
	gossipSeeds: [
		{ hostname: '192.168.0.10', port: 2113 },
		{ hostname: '192.168.0.11', port: 2113 },
		{ hostname: '192.168.0.12', port: 2113 }
	],
	credentials: {
		username: 'admin',
		password: 'changeit'
	},
	poolOptions: {
		min: 0,
		max: 10
	}
});

Config example - Clustering - DNS Discovery

const client = new EventStore.TCPClient({
	protocol: 'discover',
	hostname: 'my.host',
	port: 2113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	},
	poolOptions: {
		min: 0,
		max: 10
	}
});

Common methods(same as HTTP, just use TCP configuration)

• getEvents(streamName, startPosition, count, direction, resolveLinkTos)
• readEventsForward(streamName, startPosition, count, resolveLinkTos)
• readEventsBackward(streamName, startPosition, count, resolveLinkTos)
• writeEvent(streamName, eventType, data, metaData, options)
• writeEvents(streamName, events, options)
• deleteStream(streamName, hardDelete)

Supported Methods

close()

Close all active connections.

getEventsByType(streamName, eventTypes, startPosition, count, direction, resolveLinkTos)

Returns all events from a given stream by Event Types.

streamName

The name of the stream to read from.

eventTypes

An array of event types to filter by.

startPosition (optional)

If specified, the stream will be read starting at event number startPosition, otherwise 0

count (optional)

The number of events to be read, defaults to 1000, max of 4096

direction (optional)

The direction to the read the stream. Can be either 'forward' or 'backward'. Defaults to 'forward'.

resolveLinkTos (optional)

Resolve linked events. Defaults to true

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.TCPClient({
	hostname: 'localhost',
	port: 1113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

const eventsByType = await client.getEventsByType('TestStream', ['TestType']);

---

getAllStreamEvents(streamName, chunkSize, startPosition, resolveLinkTos)

Returns all events from a given stream.

streamName

The name of the stream to read from.

chunkSize (optional)

The amount of events to read in each call to Event Store, defaults to 1000,

startPosition (optional)

If specified, the stream will be read starting at event number startPosition, otherwise 0

resolveLinkTos (optional)

Resolve linked events. Defaults to true

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.TCPClient({
	hostname: 'localhost',
	port: 1113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

const allStreamEvents = await client.getAllStreamEvents('TestStream');

---

subscribeToStream(streamName, onEventAppeared, onDropped, resolveLinkTos)

Subscribes to a Stream (live subscription)

streamName

The name of the stream to read from.

onEventAppeared (optional)

function

onDropped

function

resolveLinkTos

Resolve linked events

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.TCPClient({
	hostname: 'localhost',
	port: 1113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

function onEventAppeared(subscription, ev) {
	processedEventCount++;
	return;
};

function onDropped(subscription, reason, error) {

};

await client.subscribeToStream('TestStream', onEventAppeared, onDropped, false);

---

subscribeToStreamFrom(streamName, fromEventNumber, onEventAppeared, onLiveProcessingStarted, onDropped, settings)

Subscribes to a Stream from a given event number (Catch up Subscription)

streamName

The name of the stream to read from.

fromEventNumber

The event number to subscribe from

onEventAppeared (optional)

function

onLiveProcessingStarted

function

onDropped

function

settings

resolveLinkTos - Whether or not to resolve link events

maxLiveQueueSize - The max amount to buffer when processing from live subscription

readBatchSize - The number of events to read per batch when reading history

debug - in debug mode(true/false)

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.TCPClient({
	hostname: 'localhost',
	port: 1113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

let processedEventCount = 0;

function onEventAppeared(subscription, ev) {
    processedEventCount++;
    return;
};

function onLiveProcessingStarted() {
    return;
}

function onDropped(subscription, reason, error) {

};

await client.subscribeToStreamFrom('TestStream', 0, onEventAppeared, onLiveProcessingStarted,onDropped);

---

eventEnumerator(streamName, direction, resolveLinkTos)

Returns an events enumerator on which events can be iterated.

streamName

The name of the stream to read from.

direction (optional)

The direction to the read the stream. Can be either 'forward' or 'backward'. Defaults to 'forward'.

resolveLinkTos (optional)

Resolve linked events. Defaults to true

Supported Functions

• next(batchSize)
• previous(batchSize)
• first(batchSize)
• last(batchSize)

batchSize

The number of events to read per enumeration.

Example

const EventStore = require('geteventstore-promise');

const client = new EventStore.TCPClient({
	hostname: 'localhost',
	port: 1113,
	credentials: {
		username: 'admin',
		password: 'changeit'
	}
});

const streamName = 'TestStream';
const enumerator = client.eventEnumerator(streamName);
const result = await enumerator.next(20);
//result
// {
//     isEndOfStream: true/false,
//     events: [ ..., ..., ... ]
// }

---