Initialization

Assuming you have completed the Python Tracker Setup for your Python project, you are now ready to initialize the Python Tracker. There are two ways to this:

1. Using the Snowplow class. This is preferable for most use cases.
2. Using the Tracker, Emitter and Subject classes. This option is useful in case you want to replace one of the internal tracker components (for instance, you want to provide a custom Emitter class).

Option 1: Initialization using the Snowplow class

The Snowplow class contains static methods to help manage Tracker objects.

Import the Snowplow class along with the required configuration objects:

from snowplow_tracker import Snowplow, EmitterConfiguration, Subject, TrackerConfiguration

The simplest tracker configuration can be instantiated with the create_tracker() method as follows:

Snowplow.create_tracker(namespace='ns', endpoint='collector.example.com')

This creates a Tracker and Emitter with default settings, with events logged to collector.example.com.

You can access a tracker in the following way:

Snowplow.get_tracker('ns')

The Snowplow class can be used to initialize trackers using the following properties:

Argument Name	Description	Required?	Default
namespace	The name of the tracker	Yes
endpoint	The collector URL events are sent to	Yes
method	The method to use: “get” or “post”	No	post
emitter_config	The emitter configuration object	No	EmitterConfiguration()
app_id	The application ID	No	None
subject	The user being tracked	No	subject.Subject()
tracker_config	The tracker configuration object	No	TrackerConfiguration()

Optionally, you may choose to use the TrackerConfiguration and EmitterConfiguration classes to configure the emitter and tracker respectively.

Tracker configuration using TrackerConfiguration

The TrackerConfiguration class contains settings to encode the payload and provide a custom json serializer. For example:

tracker_config = TrackerConfiguration(
    encode_base64=False,
    json_encoder=my_custom_encoder
)

Snowplow.create_tracker(
    namespace='ns', 
    endpoint='collector.example.com',
    tracker_config = tracker_config
)

Argument Name	Description	Default
encode_base64	Whether JSONs in the payload should be base-64 encoded.	True
json_encoder	Custom JSON serializer that gets called on non-serializable object.	None

Emitter configuration using EmitterConfiguration

The EmitterConfiguration class contains additional settings for the Emitter initialization. For example:

emitter_config = EmitterConfiguration(
    batch_size = 50,
    on_success = my_success_function,
    on_failure= my_failure_function,
    byte_limit = 25000,
    request_timeout = (10, 20),
    custom_retry_codes = {500: False, 401: True}, # Don't retry 500, retry 401
    event_store=my_custom_event_store,
    session=requests.Session
)

Snowplow.create_tracker(
    namespace='ns', 
    endpoint='collector.example.com',
    emitter_config = emitter_config
)

The full list of arguments is below:

Argument Name	Description	Default
batch_size	The maximum number of queued events before the buffer is flushed.	10
on_success	Callback executed after every HTTP request in a flush has status code 200.	None
on_failure	Callback executed if at least one HTTP request in a flush has status code other than 200.	None
byte_limit	The size event list after reaching which queued events will be flushed.	None
request_timeout	Timeout for the HTTP requests. Can be set either as single float value which applies to both "connect" AND "read" timeout, or as tuple with two float values which specify the "connect" and "read" timeouts separately.	None
custom_retry_codes	Set custom retry rules for HTTP status codes received in emit responses from the Collector. By default, retry will not occur for status codes 400, 401, 403, 410 or 422. This can be overridden here. Note that 2xx codes will never retry as they are considered successful.	None
event_store	Stores the event buffer and buffer capacity.	InMemoryEventStore
session	Persist parameters across requests by using a session object	None

Option 2: Managing "Tracker", "Emitter", and "Subject" directly

Require the Python Tracker's module into your Python code like so:

from snowplow_tracker import Tracker, Emitter, Subject

That's it - you are now ready to initialize a tracker instance.

Creating a tracker

The simplest tracker initialization only requires you to provide the Emitter's endpoint to which the tracker will log events:

e = Emitter(endpoint="collector.example.com")
t = Tracker(namespace="snowplow_tracker", emitters=e)

The tracker parameters are:

Argument Name	Description	Required?	Default
namespace	The name of the tracker instance	Yes
emitters	The emitter(s) to which events are sent	Yes
subject	The user being tracked	No	subject.Subject()
app_id	The application ID	No	None
encode_base64	Whether to enable base 64 encoding	No	True
json_encoder	Custom JSON serializer	No	None

Here is a more complete example in which every tracker parameter is set:

e = Emitter(endpoint="collector.example.com")
s = Subject().set_platform("srv")

tracker = Tracker( 
    namespace="cf", 
    emitter=e, 
    subject=s, 
    app_id="aid", 
    encode_base64=False,
    json_encoder=my_custom_encoder
)

namespace

The namespace argument is attached to every event fired by the new tracker. This allows you to later identify which tracker fired which event if you have multiple trackers running.

emitters

This can be a single emitter or an array containing at least one emitter. The tracker will send events to these emitters, which will in turn send them to a collector.

e1 = Emitter(endpoint="mycollector.com")
e2 = Emitter(endpoint="myothercollector.com", port=8080)
tracker = Tracker(namespace="snowplow_tracker", emitters=[e1, e2])

subject

The user which the Tracker will track. This should be an instance of the Subject class. You don't need to set this during Tracker construction; in this case the tracker will set a default subject, which you can also change using the Tracker.set_subject method afterwards.

app_id

The app_id argument lets you set the application ID to any string.

encode_base64

By default, unstructured events and custom contexts are encoded into Base64 to ensure that no data is lost or corrupted. You can turn encoding on or off using the Boolean encode_base64 argument.

json_encoder

This parameter allows you to customize the JSON encoder used to serialize objects added to the payload. For example:

from json.encoder import JSONEncoder
def complex_encoder(c):
    if isinstance(c,complex):
        return [c.real, c.imag]
    return JSONEncoder.default(c)

t = Tracker(
    namespace="snowplow_tracker", 
    emitter=e, 
    json_encoder=complex_encoder
)