Node.js

Detailed technical documentation on using RudderStack’s Node.js SDK to send events to various destinations.

The RudderStack Node.js SDK lets you track your customer event data from your Node.js applications and send it to your specified destinations via RudderStack.

Check out the GitHub codebase to get a more hands-on understanding of the SDK.

SDK setup requirements

To set up the RudderStack Node.js SDK, the following prerequisites must be met:

• You will need to set up a RudderStack account.

• Once signed up, set up a Node.js source in the dashboard. For more information, follow this guide. You should then see a Write Key for this source, as shown below:

• You will also need a data plane URL. Follow this section for more information on the data plane URL and where to get it.

Installing the Node.js SDK

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

npm install @rudderstack/rudder-sdk-node

Using the SDK

To use the Node.js SDK, run the following code snippet:

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

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

Running the above snippet creates a global RudderStack client object that can be used for all the subsequent event requests.

Identify

The identify call lets you identify a visiting user and capture any related information such as their name, email address, etc.

RudderStack does not store the user state in any of the server-side SDKs. Unlike the client-side SDKs that deal with only a single user at a given time, the server-side SDKs deal with multiple users at the same time. Therefore, for any of the calls supported by the Node.js SDK, you need to specify either userId or anonymousId every time.

A sample identify call is as shown:

client.identify({
  userId: "123456",
  traits: {
    name: "Name Username",
    email: "[e-mail]",
    plan: "Free",
    friends: 21,
  },
})

The identify parameters are as described below:

Field	Type	Presence	Description
anonymousId	String	Optional	A user identifier for cases where there is no userId set for the user. Either userId or anonymousId is required.
userId	String	Optional, if anonymousId is already set	The unique identifier for a user in your database.
context	Object	Optional	The dictionary of information that provides context about a message. Note that it is not directly related to the API call.
integrations	Object	Optional	The dictionary of destinations to be either enabled or disabled.
timestamp	Date	Optional	The timestamp of the message's arrival.
traits	Object	Optional	The dictionary of the traits associated with the user, such as nameor email.

Track

The track call lets you record the user actions along with their associated properties. Each user action is called an event.

A sample track call is shown below:

client.track({
  userId: "123456",
  event: "Item Viewed",
  properties: {
    revenue: 19.95,
    shippingMethod: "Premium",
  },
})

The track method parameters are as described below:

Name	Type	Presence	Description
userId	String	Required	The unique identifier for a user in your database.
event	String	Required	Name of the user event.
properties	Object	Optional	The dictionary of the properties associated with the particular event.
context	Object	Optional	The dictionary of information that provides context about a message. Note that it is not directly related to the API call.
timestamp	Date	Optional	The timestamp of the message's arrival.
anonymousId	String	Optional	A user identifier for cases where there is no userId set for the user. Either userId or anonymousId is required.
integrations	Object	Optional	A dictionary of destinations to be either enabled or disabled.

Page

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

A sample page call is as shown:

client.page({
  userId: "12345",
  category: "Food",
  name: "Pizza",
  properties: {
    url: "https://dominos.com",
    title: "Pizza",
    referrer: "https://google.com",
  },
})

The page method parameters are as described below:

Field	Type	Presence	Description
anonymousId	String	Optional	A user identifier for cases where there is no userId set for the user. Either userId or anonymousId is required.
userId	String	Optional, if anonymousId is already set	The unique identifier for a user in your database.
context	Object	Optional	The dictionary of information that provides context about a message. Note that it is not directly related to the API call.
integrations	Object	Optional	A dictionary of destinations to be either enabled or disabled.
name	String	Required	Name of the viewed page.
properties	Object	Optional	A dictionary of the properties associated with the viewed page, like url and referrer.
timestamp	Date	Optional	The timestamp of the message's arrival.

Screen

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

Field	Type	Presence	Description
anonymousId	String	Optional	Sets the user ID for cases where there is no unique identifier for the user. Either userId or anonymousId is required.
userId	String	Optional, if anonymousId is already set	Unique identifier for a particular user in your database.
context	Object	Optional	Dictionary of information that provides context about a message. However, it is not directly related to the API call.
integrations	Object	Optional	A dictionary containing the destinations to be either enabled or disabled.
name	String	Required	Name of the screen being viewed.
properties	Object	Optional	Dictionary of the properties associated with the page being viewed, such as url and referrer
timestamp	Date	Optional	The timestamp of the message's arrival.

Group

The group call lets you associate an identified user to a group - either a company, project or a team and 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:

Field	Type	Presence	Description
anonymousId	String	Optional	A user identifier for cases where there is no userId set for the user. Either userId or anonymousId is required.
userId	String	Optional, if anonymousId is already set	The unique identifier for a user in your database.
context	Object	Optional	A dictionary of information that provides context about a message. Note that it is not directly related to the API call.
integrations	Object	Optional	A dictionary of the destinations to be either enabled or disabled.
groupId	String	Required	Unique identifier for the group present in your database.
traits	Object	Optional	A dictionary of the group's properties or traits, like email or name.
timestamp	Date	Optional	The timestamp of the message's arrival.

Alias

The alias call lets you merge different identities of a known user.

alias is an advanced method that lets you change the tracked user's ID explicitly. This method is useful when managing identities for some of the downstream destinations.

A sample alias call is as shown:

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

The alias method parameters are as mentioned below:

Field	Type	Presence	Description
userId	String	Optional, if anonymousId is already set	The unique identifier for a user in your database.
context	Object	Optional	A dictionary of information that provides context about a message. Note that it is not directly related to the API call.
integrations	Object	Optional	A dictionary of the destinations to be either enabled or disabled.
previousId	String	Required	The previous unique identifier of the user.
traits	Object	Optional	The dictionary of the traits associated with the user, like nameor email.
timestamp	Date	Optional	The timestamp of the message's arrival.

For a detailed explanation of the alias call, refer to our RudderStack API Specification guide.

Node.js SDK data persistence

This feature is still in beta. Contact us on our Community Slack if you face any issues.

If the Node.js SDK fails to successfully deliver the event data to RudderStack at the first attempt, it retries the event delivery. However, if, for some reason, RudderStack is unavailable for a longer duration, there is a possibility of data loss. To prevent this scenario, RudderStack has a data persistence feature to persist the events in Redis, leading to better event delivery guarantees. Also, the SDK can retry multiple times as the queue is maintained in a different process space (in this case, Redis).

To use this feature, you will need to host a Redis server and use it as the intermediary data storage queue.

RudderStack uses Bull as the interface layer between the Node.js SDK and Redis.

A sample SDK initialization is shown below:

const client = new Analytics("write_key","server_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 => {})

To achieve the data persistence, you need to call the createPersistenceQueue method which takes two parameters as input - queueOpts and a callback. This will initialize the persistent queue.

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

Configurable parameters

Parameter	Description	Default Value
flushAt	The maximum number of events to batch and send to the server	20
flushInterval	The maximum timespan (in milliseconds) after which the events from the in-memory queue is flushed to Redis' persistence queue	20000
maxInternalQueueSize	The maximum size of the in-memory queue	20000
JobOpts.maxAttempts	The maximum number of retry attempts	10
isMultiProcessor	Determines whether to handle previously active jobs. If set to false, the previously active job will be picked up first by the processor. Otherwise, Bull moves this job to the back of the Redis queue to be picked up after the already pushed event.	false

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.

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

You can use the flush() method to ensure that all the 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');
}
)

queueOpts

As mentioned in the previous section, you need to call the createPersistenceQueue method which takes two parameters as input - queueOpts and a callback- to achieve data persistence. This method will initialize the persistent queue.

client.createPersistenceQueue(QueueOpts, callback)

Calling the createPersistenceQueue method will initialize a Redis list by calling Bull's utility methods. It will also add 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.

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:

Parameter	Description	Default Value
queueName	Name of the queue.	20
isMultiProcessor	Determines whether to handle previously active jobs. If set to false, the previously active job will be picked up first by the processor. Otherwise, Bull moves this job to the back of the Redis queue to be picked up after the already pushed event.	false
prefix	Used as the prefix to the Redis keys needed to support the Redis cluster slots.	20000
redisOpts	Refer to the RedisOpts section below	RedisOpts
jobOpts	Refer to the JobOpts section below	JobOpts

More information on this parameter can be found in the Bull docs.

RedisOpts

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

More information on this parameter can be found in the Bull docs.

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 will initialize a Redis list by calling Bull's utility methods. It will also add 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 calling callback with the error.

If the callback returns with an error, we recommend retrying 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.

Contact us

For queries on any of the sections covered in this guide, you can contact us or start a conversation in our Slack community.

If you come across any issues while using the Node.js SDK, you can open a new issue on our GitHub Issues page.