Session tracking#

Session tracking captures the session which helps to keep track of the user activity in the app.

Client session tracking is enabled by default. It can be set through the TrackerConfiguration as explained below.

iOS

let trackerConfig = TrackerConfiguration()
    .sessionContext(true)

Android (Kotlin)

val trackerConfig = TrackerConfiguration("appId")
    .sessionContext(true)

Android (Java)

TrackerConfiguration trackerConfig = new TrackerConfiguration("appId")
    .sessionContext(true);

When enabled, the tracker appends a client_session entity to each event it sends and it maintains this session information as long as the application is installed on the device.

Sessions correspond to tracked user activity. User information is set via the Client session context entity.

A session expires when no tracking events have occurred for the amount of time defined in a timeout (by default 30 minutes). The session timeout check is executed for each event tracked. If the gap between two consecutive events is longer than the timeout the session is renewed. There are two timeouts since a session can timeout in the foreground (while the app is visible) or in the background (when the app has been suspended, but not closed).

The timeouts for the session can be configured in the SessionConfiguration like in the example below:

iOS

let sessionConfig = SessionConfiguration(
    foregroundTimeout: Measurement(value: 360, unit: .seconds),
    backgroundTimeout: Measurement(value: 360, unit: .seconds)
)
Snowplow.createTracker(
    namespace: "appTracker",
    network: networkConfig,
    configurations: [trackerConfig, sessionConfig]
)

Android (Kotlin)

val sessionConfig = SessionConfiguration(
    TimeMeasure(6, TimeUnit.SECONDS),
    TimeMeasure(30, TimeUnit.SECONDS)
)
Snowplow.createTracker(applicationContext, namespace, networkConfig, sessionConfig)

Android (Java)

SessionConfiguration sessionConfig = new SessionConfiguration(
    new TimeMeasure(6, TimeUnit.SECONDS),
    new TimeMeasure(30, TimeUnit.SECONDS)
);
Snowplow.createTracker(getApplicationContext(), namespace, networkConfig, sessionConfig);

The lifecycle events (Foreground and Background events) have a role in the session expiration. The lifecycle events can be enabled as explained in App Lifecycle Tracking. Once enabled they will be fired automatically when the app moves from foreground state to background state and vice versa.

When the app moves from foreground to background, the Background event is fired. If session tracking is enabled, the session entity will be attached to the event checking the session expiration using the foreground timeout. When the app moves from background to foreground, the Foreground event is fired. If session tracking is enabled, the session entity will be attached to the event checking the session expiration using the background timeout.

For instance, with this configuration:

iOS

SessionConfiguration(
    foregroundTimeout: Measurement(value: 360, unit: .seconds),
    backgroundTimeout: Measurement(value: 15, unit: .seconds)
)

Android (Kotlin)

val sessionConfig = SessionConfiguration(
    TimeMeasure(360, TimeUnit.SECONDS),
    TimeMeasure(15, TimeUnit.SECONDS)
)

Android (Java)

SessionConfiguration sessionConfig = new SessionConfiguration(
    new TimeMeasure(360, TimeUnit.SECONDS),
    new TimeMeasure(15, TimeUnit.SECONDS)
);

the session would expire if the app is in background for more than 15 seconds, like in this example:

time: 0s - ScreenView event - foreground timeout session check - session 1
time: 3s - Background event - foreground timeout session check (3 < 360) - session 1
time: 30s - Foreground event - background timeout session check (30 > 15) - session 2

In the above example, the Foreground event triggers a new session because the time spent in background (without tracked events) is bigger than the background timeout for the session.

Session callback#

info

This feature is available since v3.1.

The tracker allows the configuration of a callback to inform the app every time a new session is created (in correspondence of a session timeout check). This can be configured in the SessionConfiguration and it provides the SessionState where all the info already tracked in the session can be accessed.

Below is an example of where the session callback is used to print out the values of session every time a new session is generated by the tracker:

iOS

...
let sessionConfig = SessionConfiguration()
    .onSessionStateUpdate { session in
        print("SessionState: id: \(session.sessionId) - index: \(session.sessionIndex) - userID: \(session.userId) - firstEventID: \(session.firstEventId)")
    }
...
let tracker = Snowplow.createTracker(namespace: kNamespace, network: networkConfig, configurations: [sessionConfig])

Android (Kotlin)

val sessionConfig = SessionConfiguration(
    TimeMeasure(6, TimeUnit.SECONDS),
    TimeMeasure(30, TimeUnit.SECONDS)
)
    .onSessionUpdate { state ->
        log(
            "Session: " + state.getSessionId()
                .toString() + "\r\nprevious: " + state.getPreviousSessionId()
                .toString() + "\r\neventId: " + state.getFirstEventId()
                .toString() + "\r\nindex: " + state.getSessionIndex()
                .toString() + "\r\nuserId: " + state.getUserId()
        )
    }

Snowplow.createTracker(applicationContext, namespace, networkConfig, sessionConfig)

Android (Java)

...
SessionConfiguration sessionConfig = new SessionConfiguration(
    new TimeMeasure(6, TimeUnit.SECONDS),
    new TimeMeasure(30, TimeUnit.SECONDS)
)
    .onSessionUpdate(state -> log(
        "Session: " + state.getSessionId()
                + "\r\nprevious: " + state.getPreviousSessionId()
                + "\r\neventId: " + state.getFirstEventId()
                + "\r\nindex: " + state.getSessionIndex()
                + "\r\nuserId: " + state.getUserId()
    ));

...
Snowplow.createTracker(getApplicationContext(), namespace, networkConfig, sessionConfig);

Decorating outgoing links using cross-navigation tracking#

note

This feature was introduced in version 6.0.0 of the iOS and Android trackers.

The decorateLink function is part of Snowplow's cross-navigation solution for tracking the movement of users across different apps and platforms.

Choose which parameters to include using a CrossDeviceParameterConfiguration object. The domainUserId and timestamp are always included automatically. Use booleans to select which properties to include in the link decoration. The tracker will derive the required values from its configuration.

This table shows the options:

Property	Description	Type	Included by default?	Value used
sessionId	Current session UUID identifier	Boolean	✅	SessionController.sessionId
subjectUserId	Custom business user identifier	Boolean	❌	SubjectController.userId
sourceId	Application identifier	Boolean	✅	TrackerConfiguration.appId
sourcePlatform	Platform of the current device	Boolean	❌	TrackerController.devicePlatform
reason	Custom information or identifier	String	❌	Custom string provided by you

The subjectUserId property is not included by default, in case it contains personal data.

iOS

let link = URL(string: "https://example.com")!
let decoratedLink = Snowplow.defaultTracker()?.decorateLink(
  link,
  // optional configuration for which information to be added to the link
  extendedParameters: CrossDeviceParameterConfiguration(sessionId: false, subjectUserId: true)
)

Android (Kotlin)

val link = Uri.parse("http://example.com")
val decoratedLink = Snowplow.defaultTracker.decorateLink(
  link,
  // optional configuration for which information to be added to the link
  CrossDeviceParameterConfiguration(sessionId = false, subjectUserId = true)
)

Android (Java)

Uri link = Uri.parse("http://example.com");
Uri decoratedLink = Snowplow.getDefaultTracker().decorateLink(link, new CrossDeviceParameterConfiguration(
    false, // sessionId
    true, // subjectUserId
    false, // sourceId
    false, // sourcePlatform
    null // reason
));

Session behavior on app restarts#

By default, each time the mobile app restarts (or when a new tracker instance is created), a new session is started regardless of whether the previous session timed out or not.

Since version 6.2 of the iOS and Android trackers, there is an option to continue the previously persisted session when the app restarts. The previous session is only continued in case the app is restarted within the configured session timeout interval. The option can be configured using SessionConfiguration:

iOS

let sessionConfig = SessionConfiguration()
    .continueSessionOnRestart(true)

Android (Kotlin)

val sessionConfig = SessionConfiguration()
    .continueSessionOnRestart(true)

Android (Java)

SessionConfiguration trackerConfig = new SessionConfiguration()
    .continueSessionOnRestart(true);

With the option enabled, every session update is persisted to UserDefaults or shared preferences storage. In case it's disabled, only session changes are persisted to UserDefaults. This means that there is more overhead when the option is enabled.