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=======================
Submitting custom pings
=======================
Custom pings can be submitted from JavaScript using:
.. code-block:: js
TelemetryController.submitExternalPing(type, payload, options)
- ``type`` - a ``string`` that is the type of the ping, limited to ``/^[a-z0-9][a-z0-9-]+[a-z0-9]$/i``.
- ``payload`` - the actual payload data for the ping, has to be a JSON style object.
- ``options`` - optional, an object containing additional options:
- ``addClientId``- whether to add the client id to the ping, defaults to ``false``
- ``addEnvironment`` - whether to add the environment data to the ping, defaults to ``false``
- ``overrideEnvironment`` - a JSON style object that overrides the environment data
``TelemetryController`` will assemble a ping with the passed payload and the specified options.
That ping will be archived locally for use with Shield and inspection in ``about:telemetry``.
If the preferences allow upload of Telemetry pings, the ping will be uploaded at the next opportunity (this is subject to throttling, retry-on-failure, etc.).
Submission constraints
----------------------
When submitting pings on shutdown, they should not be submitted after Telemetry shutdown.
Pings should be submitted at the latest within:
- the `observer notification <https://developer.mozilla.org/de/docs/Observer_Notifications#Application_shutdown>`_ ``"profile-before-change"``
- the :ref:`AsyncShutdown phase <AsyncShutdown_phases>` ``sendTelemetry``
There are other constraints that can lead to a ping submission getting dropped:
- invalid ping type strings
- invalid payload types: E.g. strings instead of objects.
- oversized payloads: We currently only drop pings >1MB, but targetting sizes of <=10KB is recommended.
Tools
=====
Helpful tools for designing new pings include:
- `gzipServer <https://github.com/mozilla/gzipServer>`_ - a Python script that can run locally and receives and saves Telemetry pings. Making Firefox send to it allows inspecting outgoing pings easily.
- ``about:telemetry`` - allows inspecting submitted pings from the local archive, including all custom ones.
Designing custom pings
======================
In general, creating a new custom ping means you don't benefit automatically from the existing tooling. Further work is needed to make data show up in re:dash or other analysis tools.
In addition to the `data collection review <https://wiki.mozilla.org/Firefox/Data_Collection>`_, questions to guide a new pings design are:
- Submission interval & triggers:
- What events trigger ping submission?
- What interval is the ping submitted in?
- Is there a throttling mechanism?
- What is the desired latency? (submitting "at least daily" still leads to certain latency tails)
- Are pings submitted on a clock schedule? Or based on "time since session start", "time since last ping" etc.? (I.e. will we get sharp spikes in submission volume?)
- Size and volume:
- What’s the size of the submitted payload?
- What's the full ping size including metadata in the pipeline?
- What’s the target population?
- What's the overall estimated volume?
- Dataset:
- Is it opt-out?
- Does it need to be opt-out?
- Does it need to be in a separate ping? (why can’t the data live in probes?)
- Privacy:
- Is there risk to leak PII?
- How is that risk mitigated?
- Data contents:
- Does the submitted data answer the posed product questions?
- Does the shape of the data allow to answer the questions efficiently?
- Is the data limited to whats needed to answer the questions?
- Does the data use common formats? (i.e. can we re-use tooling or analysis know-how)
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