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Sending custom events

Read time: 7 minutes
Last edited: Jun 17, 2022

Overview

This topic explains how to send custom events using the track feature in your SDK. The track feature is available on both client-side and server-side SDKs.

Tracking events

The track feature lets you record actions your users take in your application as events. You can connect these events to metrics in experiments in the flag dashboard. To learn more about the events SDKs send to LaunchDarkly, read Analytics events.

You can view events in the debugger. To learn more, read The debugger.

Details about each SDK's configuration are available in the SDK-specific sections below.

  • Client-side SDKs
  • Server-side SDKs

Client-side SDKs

This feature is available in the following client-side SDKs:

.NET (client-side)

Expand .NET (client-side) code sample

The Track method lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

client.Track("your-goal-key");

You can also attach custom data to your event by passing an extra parameter to Track, using the LdValue class to represent any value that can be encoded in JSON. To learn how, read LdClient.Track.

Android

Expand Android code sample

The track method lets you record actions your users take in your application. You can also attach custom JSON data to your event by passing an extra JsonElement parameter to track.

Here's how:

client.track("your-goal-key", data);

To learn more, read track.

You can also attach custom data to your event by calling TrackData or TrackMetric.

C/C++ (client-side)

Expand C/C++ (client-side) code sample

The track method allows you to record custom events in your application with LaunchDarkly:

LDClientTrack(client, "YOUR_EVENT_KEY");

To learn more, read LDClientTrack.

You can also attach custom data to your event by calling LDClientTrackData or LDClientTrackMetric.

Electron

Expand Electron code sample

Evaluating flags, either with variation() or with allFlags(), produces analytics events which you can observe on your LaunchDarkly Debugger page. The initial user you specify in the client constructor, as well as any user you specify with identify(), produces an analytics event which is how LaunchDarkly receives your user data.

You can also explicitly send an event with any data you like using the track function:

client.track('my-custom-event-key', { customProperty: someValue });

Flutter

Expand Flutter code sample

The track method lets you record actions your users take in your you do application. You can have also attach custom JSON data to your event by passing an extra LDValue parameter to track.

Here's how:

await LDClient.track('your-goal-key', data: LDValue.objectBuilder().addBool("clicked-button", true).build());

You can also attach custom data to your event using the track method with optional parameters.

iOS

Expand iOS code sample

In the iOS SDK, track is a custom event added to the LDClient event store. A client app can set a tracking event to allow client customized data analysis. After an app has called track, the app cannot remove the event from the event store. LDClient periodically transmits events to LaunchDarkly based on the frequency set in LDConfig.eventFlushInterval. The LDClient must be started and online.

After the SDK's event store is full, the SDK discards new events until the event store is cleared when it reports events to LaunchDarkly. Configure the size of the event store using LDConfig.eventCapacity. The first parameter, key, is the key for the event. The SDK does nothing with the key, which can be any string the client app sends. The second parameter, data, is the data for the event. The data parameter is optional. The SDK does nothing with the data, which can be any valid JSON item as an LDValue instance.

Optionally, you can add a metricValue parameter of type Double to track in Swift or as a required parameter to the overloaded track method in Objective-C.

let data: LDValue = ["some-custom-key": "some-custom-value", "another-custom-key": 7]
try LDClient.get()!.track(key: "MY_TRACK_EVENT_NAME", data: data)

To learn more, read the generated API documentation for Swift or Objective-C.

JavaScript

Expand JavaScript code sample

You can record custom events using the track function. In LaunchDarkly, you can connect these events to metrics in experiments. To learn more, read About Experimentation.

Call track with the event name to record custom conversion metrics.

The second argument is optional. It assists with observational analytics for Data Export destinations. With Data Export, the second argument gives additional context without saving the data to the LaunchDarkly user.

To call track:

client.track('your-event-name', { customProperty: someValue });

To learn how to attach custom data to your event with optional parameters, read track.

Tracking click and page view events in JavaScript



If you've defined click or page view goals in LaunchDarkly, they'll be sent automatically once the client has been initialized. You do not have to do anything else with the client to send click or page view goals.

To learn more about click and page view goals, read About Experimentation.

Single-page apps

The SDK automatically handles URL changes made by the HTML5 history API or by changing the URL hash fragment, and will trigger click and page view events correctly.

Analytics in JavaScript


Evaluating flags, either with variation() or with allFlags(), produces analytics events which you can observe on your LaunchDarkly Debugger page. The initial user you specify in the client constructor, as well as any user you specify with identify(), produces an analytics event which is how LaunchDarkly receives your user data.

You can also explicitly send an event with any data you like using the track function. The second argument is optional. For example:

client.track('your-event-name', { customProperty: someValue });

If you define click or page view metrics in LaunchDarkly, they are sent automatically once the client has been initialized. You do not have to do anything else with the client to send click or page view goals. The SDK will generate page view events correctly regardless of how the URL is changed, such as by the HTML5 history API, by changing the URL hash fragment, etc.

Do Not Track and ad blocking software

The JavaScript SDK respects the Do Not Track events header. If an end-user has Do Not Track enabled in their browser, the SDK does not send analytics events for flag evaluations or goals to events.launchdarkly.com. In addition, ad blocking software may block analytics events from being sent. This does not impact feature flag evaluations.

Node.js (client-side)

Expand Node.js (client-side) code sample

The track method lets you record actions your users take, giving them any event name you want. This lets you record events that take place client-side. The current user data automatically accompany the event.

Here's an example:

client.track('something-happened');
client.track('something-happened-with-custom-data', { someData: 2 });

To learn how to attach custom data to your event with optional parameters, read track.

React Native

Expand React Native code sample

The track method lets you record actions your users take in your app. You can also attach custom JSON data to your event by passing an extra parameter to track.

AvailabilitySince v2.1.0

Optionally, you can add a metricValue parameter to the track method if you are using the latest version of Experimentation.

Here's how:

client.track('YOUR_GOAL_FLAG_KEY', false);
client.track('YOUR_GOAL_FLAG_KEY_WITH_DATA', {some_data: 'value'});

To learn how to attach custom data to your event with optional parameters, read track.

Roku

Expand Roku code sample

The track method lets you record custom events in your application with LaunchDarkly.

Here's how:

REM without optional data
launchDarkly.track("YOUR_EVENT_KEY")
REM with optional data
launchDarkly.track("YOUR_EVENT_KEY", {"customField": 123})
REM with optional numeric metric
launchDarkly.track("YOUR_EVENT_KEY", invalid, 52.3)

Server-side SDKs

This feature is available in the following server-side SDKs:

.NET (server-side)

Expand .NET (server-side) code sample

The Track method lets you record actions users take on your site. This lets you record events that take place on your server. In LaunchDarkly, you can tie these events to goals in A/B tests.

Here's an example:

client.Track("your-goal-key", user);

You can also attach custom data to your event by passing an extra parameter to Track. To do this, use the LdValue type, which can contain any kind of data supported by JSON. You can also pass another parameter for a custom metric value.

Apex

Expand Apex code sample

The track method lets you record actions your users take in your you do application. You can also attach custom JSON data to your event by passing an LDValue parameter to track, or a custom metric value by passing a Double parameter.

Here's how:

client.track(user, 'your-goal-key', 52.3, LDValue.of('my value'));

To learn how to attach custom data to your event with extra parameters, read Other methods.

C/C++ (server-side)

Expand C/C++ (server-side) code sample

The LDClientTrack function lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

LDClientTrack(client, "your-goal-key", user, NULL);

To learn more, read LDClientTrack().

You can also attach custom data to your event by calling LDClientTrackMetric().

Erlang

Expand Erlang code sample

The track function lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

ldclient:track(<<"YOUR-METRIC-KEY">>, #{key => <<"aa0ceb">>}, #{data => <<"example">>})

To learn more, read track.

You can also attach a JSON object containing arbitrary data to your event, or a custom metric value. To learn how, read track_metric.

Go

Expand Go code sample

The Track methods allow you to record actions your users take on your site. This lets you record events that take place on your server.

In this example, we use TrackEvent to send an event called completed-purchase. This event can correspond to a metric with the same key.

Here's how:

client.TrackEvent("completed-purchase", user)

You can also attach custom data to your event by calling TrackData, which takes an extra parameter. Or, if you are using experimentation, you can specify a numeric metric with TrackMetric.

Haskell

Expand Haskell code sample

The track function lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

track client user "your-metric-key" Nothing Nothing

You can also attach a JSON object containing arbitrary data to your event, or a custom metric value. To learn how, read track.

Java

Expand Java code sample

The track method lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

client.track("your-goal-key", user);

You can also attach custom JSON data to your event with an alternate version of track, trackData. You can set the data to any value that can be represented in JSON. To learn more, read LDValue.

If you are using Experimentation, you can specify a numeric metric with trackMetric.

Lua

Expand Lua code sample

The track method lets you record actions your users take. This lets you record events that take place on your server.

Here's how:

client:track("your-goal-key", user);

You can also attach an object containing arbitrary data to your event. To learn how, read track.

Node.js (server-side)

Expand Node.js (server-side) code sample

The track method lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

client.track('your-goal-key', user);

You can also attach custom data to your event with optional parameters. To learn how, read track.

PHP

Expand PHP code sample

The track method lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

$client->track("your-goal-key", user);

You can also attach custom data, including anything that can be marshaled to JSON, to your event by passing an extra parameter to track. To learn how, read track().

Python

Expand Python code sample

The track method lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

ldclient.get().track("your-goal-key", user)

You can also attach custom data to your event with optional parameters. To learn how, read track.

Ruby

Expand Ruby code sample

The track method lets you record actions your users take on your site. This lets you record events that take place on your server.

Here's how:

client.track("your-goal-key", user)

You can also attach an extra hash containing arbitrary data to your event. To learn how, read track.

Rust

Expand Rust code sample

The track methods allow you to record actions your users take on your site. This lets you record events that take place on your server.

In this example, we use track_event to send an event called completed-purchase. This event can correspond to a metric with the same key.

Here's how:

client.track_event(user, "completed-purchase");

You can also attach custom data to your event by calling track_data, which takes an extra parameter. Or, if you are using experimentation, you can specify a numeric metric with track_metric.