Node.js SDK

RudderStack’s Node.js SDK lets you track and send the events from your Node applications to the specified destinations.

See the Node.js SDK GitHub codebase for implementation-specific details.

SDK setup requirements

• Sign up for RudderStack.
• Set up a Node.js source in the dashboard. Note the write keyThe write key (or source write key) is a unique identifier for your source. RudderStack uses this key to send events from a source to the specified destination. for this source.
• You will also need the data plane URL associated with your RudderStack workspace.

The Setup tab in the RudderStack dashboard (seen above) has the SDK installation snippet containing both the write key and the data plane URL. Copy it to integrate the Node.js SDK into your application.

Installing the Node.js SDK

To install the RudderStack Node.js SDK using npm, run the following command:

npm install @rudderstack/rudder-sdk-node

Initializing the SDK

Run the following snippet to initialize the Node.js SDK. It creates a global RudderStack client object that can be used for all subsequent event requests.

const RudderAnalytics = require("@rudderstack/rudder-sdk-node")

// RudderStack requires the batch endpoint of the server you are running
const client = new RudderAnalytics(WRITE_KEY, <DATA_PLANE_URL>/v1/batch)

const RudderAnalytics = require('@rudderstack/rudder-sdk-node');

const client = new RudderAnalytics(WRITE_KEY, {
  dataPlaneUrl: DATA_PLANE_URL, // default: https://hosted.rudderlabs.com

  // More initialization options
});

SDK initialization options

The RudderStack Node.js SDK provides the following parameters which you can pass during the SDK initialization:

The following initialization parameters are only available for RudderStack Node.js SDK v2.x.x and above:

For gzipping requests, your rudder-server must be on v1.4.0 or above. Otherwise, your requests will fail.

Sending events

RudderStack does not store or persist the user state in any of the server-side SDKs.

Unlike the client-side SDKs that deal with a single user at a given time, the server-side SDKs deal with multiple users simultaneously. Therefore, you must specify either the userId or anonymousId every time while making any API calls supported by the Node.js SDK.

Identify

The identify call lets you identify a visiting user and associate them to their actions. It also lets you record the traits about them like their name, email address, etc.

A sample identify call is as shown:

client.identify({
  userId: "1hKOmRA4GRlm",
  traits: {
    name: "Alex Keener",
    email: "alex@example.com",
    plan: "Free",
    friends: 21,
  },
})

The identify parameters are as described below:

Track

The track call lets you track the user actions along with any properties associated with them.

A sample track call is shown below:

client.track({
  userId: "1hKOmRA4GRlm",
  event: "Item Viewed",
  properties: {
    revenue: 19.95,
    shippingMethod: "Premium",
  },
})

The track method parameters are as described below:

Page

The page call allows you to record the page views on your application, along with the other relevant information about the page.

A sample page call is as shown:

client.page({
  userId: "1hKOmRA4GRlm",
  category: "Food",
  name: "Pizza",
  properties: {
    url: "https://example.com",
    title: "Pizza",
    referrer: "https://google.com",
  },
})

The page method parameters are as described below:

Screen

The screen call is the mobile equivalent of the page call. It lets you record the screen views on your mobile app along with other relevant information about the screen.

A sample screen call is as shown:

client.screen({
  userId: "12345",
  category: "Food",
  name: "Pizza",
  properties: {
    screenSize: 10,
    title: "Pizza",
    referrer: "https://google.com",
  },
})

The screen method parameters are as described below:

Group

The group call lets you link an identified user with a group, such as a company, organization, or an account. It also lets you record any custom traits or properties associated with that group.

A sample group call is as shown:

client.group({
  userId: "12345",
  groupId: "1",
  traits: {
    name: "Company",
    description: "Google",
  },
})

The group method parameters are as follows:

Alias

The alias call lets you merge different identities of a known user. It is an advanced method that lets you change the tracked user’s ID explicitly. You can use alias for managing the user’s identity in some of the downstream destinations.

RudderStack supports sending alias events only to select downstream destinations. Refer to the destination-specific documentation for more details.

A sample alias call is as shown:

client.alias({
  previousId: "old_id",
  userId: "new_id",
})

The alias method parameters are as mentioned below:

Data persistence

This is a beta feature. Contact the RudderStack team on Slack if you face any issues.

If the Node.js SDK fails to deliver the events to RudderStack in the first attempt, it retries the event delivery. However, if RudderStack is unavailable for a longer duration, there is a possibility of data loss. To prevent this scenario, the SDK has the data persistence feature where the event data is persisted in Redis, guaranteeing event delivery. Simultaneously, the SDK can retry multiple times as the queue is maintained in a different process space (Redis).

To use this feature, you will need to host a Redis server to use it as the intermediary data storage queue. RudderStack uses Bull as the interface layer between the Node.js SDK and Redis.

To achieve data persistence, you need to call the createPersistenceQueue method which takes two parameters - queueOpts and callback. It initializes the persistent queue. A sample SDK initialization is shown below:

const client = new Analytics("write_key", "DATA_PLANE_URL/v1/batch", {
  flushAt: <number> = 20,
  flushInterval: <ms> = 20000
  // the max number of elements that the SDK can hold in memory,
  // this is different than the Redis list created when persistence is enabled.
  // This restricts the data in-memory when Redis is down, unreachable etc.
  maxInternalQueueSize: < number > = 20000
});

client.createPersistenceQueue({
  redisOpts: {
    host: "localhost"
  }
}, err => {})

const client = new Analytics("WRITE_KEY", {
  dataPlaneUrl: DATA_PLANE_URL // default: https://hosted.rudderlabs.com with default path set to /v1/batch
  flushAt: <number> = 20,
  flushInterval: <ms> = 20000
  // the max number of elements that the SDK can hold in memory,
  // this is different than the Redis list created when persistence is enabled.
  // This restricts the data in-memory when Redis is down, unreachable etc.
  maxInternalQueueSize: < number > = 20000
});

client.createPersistenceQueue({
  redisOpts: {
    host: "localhost"
  }
}, err => {})

If the createPersistenceQueue method is not called after initializing the SDK, the SDK will work without any persistence.

queueOpts

The syntax for createPersistenceQueue method is as follows:

client.createPersistenceQueue(QueueOpts, callback)

A sample queueOpts initialization is shown below:

queueOpts {
  queueName ?: string = rudderEventsQueue,
  isMultiProcessor ?: boolean = false
  // pass a value without the {}, this will used as prefix to Redis keys,
  // needed to support Redis cluster slots.
  prefix?: string = {rudder},
  redisOpts : RedisOpts,
  jobOpts?: JobOpts
}

The specification of the different queueOpts parameters is listed in the following table:

For more information on these parameters, refer to the Bull docs.

If the same queue (RudderStack SDK initialized with the same queue name) is used in case of multiple servers (server-side SDKs), set the value of isMultiProcessor to true as event ordering is not applicable in this case.

RedisOpts

RedisOpts {
  port?: number = 6379;
  host?: string = localhost;
  db?: number = 0;
  password?: string;
}

JobOpts

JobOpts {
  maxAttempts?: number = 10
}

callback

In case of an error, the createPersistenceQueue method returns a callback. You should retry sending the events in this scenario.

// createPersistenceQueue calls this with error or nothing(in case of success), // user should retry in case of error
callback: function(error) || function()

Calling the createPersistenceQueue method initializes a Redis list by calling the Bull’s utility methods. It also adds a single job processor for the processing (making requests to RudderStack) jobs that are pushed into the list. Any error encountered while doing this leads to a callback with the error.

If the callback returns with an error, RudderStack recommends retry calling createPersistenceQueue with a backoff.

Event flow

• Calling the SDK methods like track, page, identify, etc. pushes the events to an in-memory array.
• The events from the array are flushed as a batch to the Redis persistence based on the flushAt and flushInterval settings. The in-memory array has a maximum size of maxInternalQueueSize. Once this size limit is reached, __the events won’t be accepted if not drained to the other side (cases where Redis connection is slow or the Redis server is not reachable).
• The processor will take the batch from the Redis list and make a request to RudderStack. In case of an error, the processor will retry sending the data again if the error can be retried (errors with status code 5xx and 429). The retry will go up to JobOpts.maxAttempts with an exponential backoff of power 2 with max backoff of 30 seconds.
• If the job fails even after JobOpts.maxAttempts, it will not be retried again and pushed to a failed queue. You can retry them later manually using Bull’s utility methods listed here or get them from Redis directly.
• There might be a scenario where the node process dies with the jobs still in active state (not completed nor failed but in the process of sending/retrying). Since the RudderStack SDK has only 1 processor for sending events (this count should always be 1), the next time the SDK is initialized and createPersistenceQueue is called, the jobs will be picked up first by the processor to get processed to maintain event ordering based on the value of QueueOpts.isMultiProcessor.
• For multiple servers (SDK) connecting to the same queue (QueueOpts.queueName), there will be multiple processors fetching events from the same queue and event ordering won’t be implemented. Hence, QueueOpts.isMultiProcessor should be set to true.

FAQ

How to ensure that all my events in the queue are processed?

You can use the flush() method to ensure that all events in the queue are processed. The following example highlights the use of flush() with a callback:

client.flush(function(err, batch){
  console.log('Flushing done');
})

How does the Node.js SDK handle events larger than 32KB?

The Node.js SDK accepts and sends each event greater than 32KB as a single batch and sends them to the backend.

Does the Node.js SDK support event ordering?

The Node.js SDK does not support event ordering by default.

Questions? Contact us by email or on Slack