The events ping


The events ping's purpose is to transport event metric information.

If the application crashes, an events ping is generated next time the application starts with events that were not sent before the crash.

Platform availability

SDKKotlinSwiftPythonRustJavaScriptFirefox Desktop
events ping


The events ping is automatically submitted under the following circumstances:

  1. If there are any recorded events to send when the application becomes inactive (on mobile, this means going to background).

  2. When the queue of events exceeds Glean.configuration.maxEvents (default 1 for Glean.js, 500 for all other SDKs). This configuration option can be changed at initialization.

  3. If there are any unsent events found on disk when starting the application. (This results in this ping never containing the glean.restarted event.)

Python and JavaScript caveats

Since the Glean Python and JavaScript SDKs don't have a generic concept of "inactivity", case (1) above cannot be handled automatically.

On Python, users can call the handle_client_inactive API to let Glean know the app is inactive and that will trigger submission of the events ping.

On JavaScript there is no such API and only cases (2) and (3) apply.


At the top-level, this ping contains the following keys:

  • client_info: The information common to all pings.

  • ping_info: The information common to all pings.

  • events: An array of all of the events that have occurred since the last time the events ping was sent.

Each entry in the events array is an object with the following properties:

  • "timestamp": The milliseconds relative to the first event in the ping.

  • "category": The category of the event, as defined by its location in the metrics.yaml file.

  • "name": The name of the event, as defined in the metrics.yaml file.

  • "extra" (optional): A mapping of strings to strings providing additional data about the event. Keys are restricted to 40 UTF-8 bytes while values in the extra object are limited a maximum length of 500 UTF-8 bytes.

Example event JSON

  "ping_info": {
    "experiments": {
      "third_party_library": {
        "branch": "enabled"
    "seq": 0,
    "start_time": "2019-03-29T09:50-04:00",
    "end_time": "2019-03-29T10:02-04:00"
  "client_info": {
    "telemetry_sdk_build": "0.49.0",
    "first_run_date": "2019-03-29-04:00",
    "os": "Android",
    "android_sdk_version": "27",
    "os_version": "8.1.0",
    "device_manufacturer": "Google",
    "device_model": "Android SDK built for x86",
    "architecture": "x86",
    "app_build": "1",
    "app_display_version": "1.0",
    "client_id": "35dab852-74db-43f4-8aa0-88884211e545"
  "events": [
      "timestamp": 0,
      "category": "examples",
      "name": "event_example",
      "extra": {
        "metadata1": "extra",
        "metadata2": "more_extra"
      "timestamp": 1000,
      "category": "examples",
      "name": "event_example"