“core” ping¶

This mobile-specific ping is intended to provide the most critical data in a concise format, allowing for frequent uploads.

Since this ping is used to measure retention, it should be sent each time the browser is opened.

Submission will be per the Edge server specification:

/submit/telemetry/docId/docType/appName/appVersion/appUpdateChannel/appBuildID

docId is a UUID for deduping
docType is “core”
appName is “Fennec”
appVersion is the version of the application (e.g. “46.0a1”)
appUpdateChannel is “release”, “beta”, etc.
appBuildID is the build number

Note: Counts below (e.g. search & usage times) are “since the last ping”, not total for the whole application lifetime.

Structure:

{
  "v": 7, // ping format version
  "clientId": <string>, // client id, e.g.
                        // "c641eacf-c30c-4171-b403-f077724e848a"
  "seq": <positive integer>, // running ping counter, e.g. 3
  "locale": <string>, // application locale, e.g. "en-US"
  "os": <string>, // OS name.
  "osversion": <string>, // OS version.
  "device": <string>, // Build.MANUFACTURER + " - " + Build.MODEL
                      // where manufacturer is truncated to 12 characters
                      // & model is truncated to 19 characters
  "arch": <string>, // e.g. "arm", "x86"
  "profileDate": <pos integer>, // Profile creation date in days since
                                // UNIX epoch.
  "defaultSearch": <string>, // Identifier of the default search engine,
                             // e.g. "yahoo".
  "distributionId": <string>, // Distribution identifier (optional)
  "created": <string>, // date the ping was created
                       // in local time, "yyyy-mm-dd"
  "tz": <integer>, // timezone offset (in minutes) of the
                   // device when the ping was created
  "sessions": <integer>, // number of sessions since last upload
  "durations": <integer>, // combined duration, in seconds, of all
                                // sessions since last upload
  "searches": <object>, // Optional, object of search use counts in the
                        // format: { "engine.source": <pos integer> }
                        // e.g.: { "yahoo.suggestion": 3, "other.listitem": 1 }
  "experiments": [<string>, …], // Optional, array of identifiers
                                // for the active experiments
}

Field details¶

device¶

The device field is filled in with information specified by the hardware manufacturer. As such, it could be excessively long and use excessive amounts of limited user data. To avoid this, we limit the length of the field. We’re more likely have collisions for models within a manufacturer (e.g. “Galaxy S5” vs. “Galaxy Note”) than we are for shortened manufacturer names so we provide more characters for the model than the manufacturer.

distributionId¶

The distributionId contains the distribution ID as specified by preferences.json for a given distribution. More information on distributions can be found here.

It is optional.

defaultSearch¶

On Android, this field may be null. To get the engine, we rely on SearchEngineManager#getDefaultEngine, which searches in several places in order to find the search engine identifier:

Shared Preferences
The distribution (if it exists)
The localized default engine

If the identifier could not be retrieved, this field is null. If the identifier is retrieved, we attempt to create an instance of the search engine from the search plugins (in order):

In the distribution
From the localized plugins shipped with the browser
The third-party plugins that are installed in the profile directory

If the plugins fail to create a search engine instance, this field is also null.

This field can also be null when a custom search engine is set as the default.

sessions & durations¶

On Android, a session is the time when Firefox is focused in the foreground. sessions tracks the number of sessions since the last upload and durations is the accumulated duration in seconds of all of these sessions. Note that showing a dialog (including a Firefox dialog) will take Firefox out of focus & end the current session.

An implementation that records a session when Firefox is completely hidden is preferrable (e.g. to avoid the dialog issue above), however, it’s more complex to implement and so we chose not to, at least for the initial implementation.

profileDate¶

On Android, this value is created at profile creation time and retrieved or, for legacy profiles, taken from the package install time (note: this is not the same exact metric as profile creation time but we compromised in favor of ease of implementation).

Additionally on Android, this field may be null in the unlikely event that all of the following events occur:

The times.json file does not exist
The package install date could not be persisted to disk

The reason we don’t just return the package install time even if the date could not be persisted to disk is to ensure the value doesn’t change once we start sending it: we only want to send consistent values.

searches¶

In the case a search engine is added by a user, the engine identifier “other” is used, e.g. “other.<source>”.

Sources in Android are based on the existing UI telemetry values and are as follows:

actionbar: the user types in the url bar and hits enter to use the default search engine
listitem: the user selects a search engine from the list of secondary search engines at the bottom of the screen
suggestion: the user clicks on a search suggestion or, in the case that suggestions are disabled, the row corresponding with the main engine

Other parameters¶

HTTP “Date” header¶

This header is used to track the submission date of the core ping in the format specified by rfc 2616 sec 14.18, et al (e.g. “Tue, 01 Feb 2011 14:00:00 GMT”).

Version history¶

v7: added sessionCount & sessionDuration
v6: added searches
v5: added created & tz
v4: profileDate will return package install time when times.json is not available
v3: added defaultSearch
v2: added distributionId
v1: initial version

Notes¶

distributionId (v2) actually landed after profileDate (v4) but was uplifted to 46, whereas profileDate landed on 47. The version numbers in code were updated to be increasing (bug 1264492) and the version history docs rearranged accordingly.

Android implementation notes¶

On Android, the uploader has a high probability of delivering the complete data for a given client but not a 100% probability. This was a conscious decision to keep the code simple. The cases where we can lose data:

Resetting the field measurements (including incrementing the sequence number) and storing a ping for upload are not atomic. Android can kill our process for memory pressure in between these distinct operations so we can just lose a ping’s worth of data. That sequence number will be missing on the server.
If we exceed some number of pings on disk that have not yet been uploaded, we remove old pings to save storage space. For those pings, we will lose their data and their sequence numbers will be missing on the server.

Note: we never expect to drop data without also dropping a sequence number so we are able to determine when data loss occurs.