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, see Adding a source. 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:

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npm install @rudderstack/rudder-sdk-node

Using the SDK

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

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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.

A sample identify call is as shown:

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client.identify({
  userId: "123456",
  traits: {
    name: "Name Username",
    email: "name@website.com",
    plan: "Free",
    friends: 21,
  },
})

The identify parameters are as described below:

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:

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client.track({
  userId: "123456",
  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 website along with the other relevant information about the viewed page.

A sample page call is as shown:

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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:

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:

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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 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:

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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.

A sample alias call is as shown:

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

The alias method parameters are as mentioned below:

Node.js SDK data persistence

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).

A sample SDK initialization is shown below:

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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.

Configurable parameters

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:

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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:

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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:

RedisOpts

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

JobOpts

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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.

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// 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.

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.