Collecting data with Trackers and Webhooks

  1. Home
  2. Docs
  3. Collecting data with Trackers and Webhooks
  4. Trackers – collecting data from your own applications
  5. C++ Tracker
  6. Initialisation


Designing how and what to track in your app is an important decision. Check out our docs about tracking design here.

Import the library

Import the C++ Tracker library and use the snowplow namespace like so:

#include "snowplow/snowplow.hpp" using namespace snowplow;
Code language: C++ (cpp)

That’s it – you are now ready to initialize a tracker instance that you will use to track events. There are 3 ways to do that:

  1. Create a tracker with default configuration using the Snowplow interface.
  2. Create a tracker with custom configuration using the Snowplow interface.
  3. Create and manage TrackerEmitter, and ClientSession directly.

Option 1: Creating a tracker with default configuration using the “Snowplow” interface

The Snowplow class provides static methods that let you easily create a new tracker. It can be as simple as:

auto tracker = Snowplow::create_tracker( "ns", // tracker namespace used to identify the tracker "https://com.acme.collector", // Snowplow collector URL POST, // HTTP method used to send events to the collector "events.db" // Relative path to an SQLite database used for event queue and session tracking );
Code language: C++ (cpp)

Optionally, you may choose to attach a Subject instance with information about the user and device (see the next page on Adding data to learn more about the Subject):

auto subject = std::make_shared<Subject>() // initialize a C++ shared pointer for the Subject subject->set_user_id("a-user-id"); auto tracker = Snowplow::create_tracker("ns", "https://com.acme.collector", POST, "events.db", subject);
Code language: C++ (cpp)

Finally, client session tracking will be automatically enabled and session information will be attached to all events (see documentation on Client sessions for more details). If you wish to disable session tracking, pass false as the last argument:

auto tracker = Snowplow::create_tracker("ns", "https://com.acme.collector", POST, "events.db", subject, false);
Code language: PHP (php)

After you create a tracker, you can access it from anywhere using it’s namespace:

auto tracker = Snowplow::get_tracker("ns");
Code language: PHP (php)

You can also access the default tracker using Snowplow::get_default_tracker(). The default tracker is the first initialized tracker (unless it is removed). If you have multiple trackers, you can choose the default tracker by calling Snowplow::set_default_tracker(tracker2).

To remove reference of previously initialized tracker from the Snowplow interface (the tracker will be deleted once all remaininig references to it are deleted):

Code language: CSS (css)

Option 2: Creating a tracker with custom configuration using the “Snowplow” interface

There are a number of settings that you may want to customize when creating a tracker instance. You can make use of configuration objects to provide custom configuration for the tracker:

TrackerConfiguration tracker_config( "namespace", // tracker namespace "app-id", // application ID mob // platform that the tracker runs on ); tracker_config.set_desktop_context(false); // do not attach a desktop context entity to events (on by default) NetworkConfiguration network_config("https://com.acme.collector", POST); // collector URL and method EmitterConfiguration emitter_config("sp.db"); // event queue DB path if SQLite or custom `EventStore` instance emitter_config.set_batch_size(500); // maximum number of events to send at a time SessionConfiguration session_config( "sp.db", // session DB path if SQLite (usually same as event queue) or custom `SessionStore` instance 5000, // foreground timeout in ms 5000 // background timeout in ms ); auto tracker = Snowplow::create_tracker(tracker_config, network_config, emitter_config, session_config);
Code language: C++ (cpp)

Tracker configuration using “TrackerConfiguration”

TrackerConfiguration contains settings to identify and configure the tracker. It’s constructor takes 3 attributes:

Constructor attributeDescriptionDefault
name_spaceTracker namespace to identify the tracker and also attach as a property to tracked events.None
app_idApplication ID.“”
platformEnum of the platform the Tracker is running on, can be one of: web, mob, pc, app, srv, tv, cnsl, iotsrv

It further provides 2 optional setter functions:

set_use_base64Whether to use base64 encoding in events.true
set_desktop_contextWhether to add a desktop_context, which gathers information about the device the tracker is running on, to each event.true

Network configuration using “NetworkConfiguration”

NetworkConfiguration has only two properties set in it’s constructor to configure the Snowplow collector:

Constructor attributeDescriptionDefault
collector_urlFull URL of the Snowplow collector including the protocol (or defaults to HTTPS if protocol not present).None
methodHTTP method to use when sending events to collector – GET or POST.POST
curl_cookie_filePath to a file where to store cookies in case http_client is nullptr and the CURL HTTP client is used – only relevant under Linux (CURL is not used under Windows and macOS)In-memory cookie storage with CURL on Linux, platform native storage on Windows and macOS

Additionally, it provides the following setter functions:

set_http_clientUnique pointer to a custom HTTP client to send GET and POST requests with.Platform-specific implementation.

Emitter configuration using “EmitterConfiguration”

EmitterConfiguration brings additional settings for the constructor. It provides two constructors that accept the event store either as a path to the SQLite database or a custom EventStore object. The following configurations are identical:

EmitterConfiguration config1("sp.db"); auto storage = std::make_shared<SqliteStorage>("sp.db"); EmitterConfiguration config2(storage); // you can also pass a custom `EventStore`
Code language: C++ (cpp)

Additionally, it provides the following setter functions:

set_batch_sizeThe maximum amount of events to send at a time.250 events
set_byte_limit_getThe byte limit when sending a GET request.40000 bytes
set_byte_limit_postThe byte limit when sending a POST request.40000 bytes
set_request_callbackSet a callback to call after emit requests are made with the resulting emit status (see page about Emitter for more info).None
set_custom_retry_for_status_codeSet a custom retry rule for when the HTTP status code is received in emit response from Collector (see page about Emitter for more details).None

Session configuration using “SessionConfiguration”

SessionConfiguration is an optional attribute in create_tracker. If passed, session tracking will be enabled with the given configuration. If not passed, session tracking will not be enabled. The constructor takes 3 attributes:

Constructor attributeDescriptionDefault
session_store or db_nameYou may either pass a path to an SQLite database to be used for session storage or a custom implementation of SessionStore similar as for EventStore in EmitterConfiguration.None
foreground_timeoutTimeout in ms for updating the session when the app is in background.30 minutes
background_timeoutTimeout in ms for updating the session when the app is in foreground.30 minutes

Option 3: Managing “Tracker”, “Emitter”, and “ClientSession” directly

The third option to initialise a new tracker is to instantiate it and the related components directly. This option is suitable in case you want supply a custom emitter or client session implementation. If you don’t want to do that, we recommend using Option 2 which gives you the same configuration options with a simpler API.

The following example takes you through the steps needed to initialize a storage, emitter, subject, client session, and tracker:

#include "snowplow/snowplow.hpp" // 1. create storage for event queue and session information auto storage = std::make_shared<SqliteStorage>("sp.db"); // 2. create an emitter for sending event to Snowplow collector auto emitter = std::make_shared<Emitter>(storage, "com.acme.collector"); // 3. create a subject with user and device information auto subject = std::make_shared<Subject>(); subject->set_user_id("a-user-id"); // 4. optionally create a client_session for session tracking auto client_session = std::make_shared<ClientSession>(storage, 5000, 5000); // 5. finally, create the tracker instance auto tracker = std::make_shared<Tracker>(emitter, subject, client_session, "pc", "app_id", "ns");
Code language: C++ (cpp)

Once you initialize the tracker, you can optionally register it with the Snowplow interface:

Code language: C++ (cpp)

This will make accessible from anywhere using Snowplow::get_tracker("ns").

The following will explain the individual components shown in the above code sample in more detail.


The storage has two functions in the example above – it is used by the emitter to persist an event queue with events to be sent, and it is used by the client_session to persist the current session. The tracker provides an SQL storage (SqliteStorage) implementation, but you may introduce your own storage as described in “Emitters” and “Client Sessions”.


Emitter is a required component responsible for sending tracked events to the collector.

Accepts an argument of an Emitter instance pointer; if the object is NULL will throw an exception. See Emitters for more on emitter configuration.

Argument NameDescriptionRequired?Default
event_storeDefines the database to use for event queueYes
uriThe collector URI (excluding protocol) to send events toYes
methodThe request type to use (GET or POST)NoPOST
protocolThe protocol to use (HTTP or HTTPS)NoHTTPS
batch_sizeThe maximum amount of events to send at a timeNo250 events
byte_limit_postThe byte limit when sending a POST requestNo40000 bytes
byte_limit_getThe byte limit when sending a GET requestNo40000 bytes
http_clientUnique pointer to a custom HTTP client to send GET and POST requests withNoPlatform-specific implementation.
curl_cookie_filePath to a file where to store cookies in case http_client is nullptr and the CURL HTTP client is used – only relevant under Linux (CURL is not used under Windows and macOS)NoIn-memory cookie storage with CURL on Linux, platform native storage on Windows and macOS


The user which the Tracker will track. Accepts an argument of a Subject instance pointer.

You don’t need to set this during Tracker construction; you can use the tracker.set_subject(...) method afterwards. In fact, you don’t need to create a subject at all. If you don’t, though, your events won’t contain user-specific data such as timezone and language.

Client session

The client sessions which the Tracker will attach to each event. Accepts an argument of a ClientSession instance pointer.

Adds the ability to attach a ClientSession context to each event that leaves the Tracker. This object will persistently store information about the sessions that have occurred for the life of the application – unless the database is destroyed.


The tracker instance lets you track events. You should maintain a reference to the initialized tracker during the app lifetime.

Argument NameDescriptionRequired?Default
emitterThe emitter to which events are sentYes
subjectThe user being trackedNonullptr
client_sessionClient session recordingNonullptr
platformThe platform the Tracker is running onNo“srv”
app_idThe application IDNo“”
name_spaceThe namespace of the tracker instance used to identify the tracker.No“”
use_base64Whether to enable base 64 encoding. Defaults to true to ensure that no data is lost or corrupted.Notrue
desktop_contextWhether to add a desktop_context to eventsNotrue

The desktop_context gathers extra information about the device it is running on and sends it along with every event that is made by the Tracker.

An example of the data in this context:

{ "deviceManufacturer": "Apple Inc.", "deviceModel": "MacPro3,1", "deviceProcessorCount": 8, "osIs64Bit": true, "osServicePack": "", "osType": "macOS", "osVersion": "10.11.2" }
Code language: JSON / JSON with Comments (json)

For more information the raw JsonSchema can be found here.

If you’d like to learn more about Snowplow BDP you can book a demo with our team, or if you’d prefer, you can try Snowplow technology for yourself quickly and easily.