Bug 1156712 - Part 4: Update the ping submission documentation. r=vladan

toolkit/components/telemetry/docs/pings.rst

@@ -14,11 +14,23 @@ It contains some basic information shared between different ping types, the :doc
 Submission
 ==========
 
-Pings are submitted via a common API on ``TelemetryController``. It allows callers to choose a custom retention period that determines how long pings are kept on disk if submission wasn't successful.
-If a ping failed to submit (e.g. because of missing internet connection), Telemetry will retry to submit it until its retention period is up.
+Pings are submitted via a common API on ``TelemetryController``.
+If a ping fails to successfully submit to the server immediately (e.g. because
+of missing internet connection), Telemetry will store it on disk and retry to
+send it until the maximum ping age is exceeded (14 days).
 
 *Note:* the :doc:`main pings <main-ping>` are kept locally even after successful submission to enable the HealthReport and SelfSupport features. They will be deleted after their retention period of 180 days.
 
+Sending of pending pings starts as soon as the delayed startup is finished. They are sent in batches, newest-first, with up
+to 10 persisted pings per batch plus all unpersisted pings.
+The send logic then waits for each batch to complete.
+
+If it succeeds we trigger the next send of a ping batch. This is delayed as needed to only trigger one batch send per minute.
+
+If ping sending encounters an error that means retrying later, a backoff timeout behavior is
+triggered, exponentially increasing the timeout for the next try from 1 minute up to a limit of 120 minutes.
+Any new ping submissions and "idle-daily" events reset this behavior as a safety mechanism and trigger immediate ping sending.
+
 The telemetry server team is working towards `the common services status codes <https://wiki.mozilla.org/CloudServices/DataPipeline/HTTPEdgeServerSpecification#Server_Responses>`_, but for now the following logic is sufficient for Telemetry:
 
 * `2XX` - success, don't resubmit