“main” ping¶
This is the “main” Telemetry ping type, whose payload contains most of the measurements that are used to track the performance and health of Firefox in the wild. It includes histograms and other performance and diagnostic data.
This ping may be triggered for one of many reasons documented by the reason
field:
aborted-session
- this ping is regularly saved to disk (every 5 minutes), overwriting itself, and deleted at shutdown. If a previous aborted session ping is found at startup, it gets sent to the server. The first aborted-session ping is generated as soon as Telemetry startsenvironment-change
- the Environment changed, so the session measurements got reset and a new subsession startsshutdown
- triggered when the browser session ends. For the first browsing session, this ping is saved to disk and sent on the next browser restart. From the second browsing session on, this ping is sent immediately on shutdown using the Ping Sender, unless the OS is shutting downdaily
- a session split triggered in 24h hour intervals at local midnight. If anenvironment-change
ping is generated by the time it should be sent, the daily ping is rescheduled for the next midnightsaved-session
- the “classic” Telemetry payload with measurements covering the whole browser session (only submitted for a transition period)
Most reasons lead to a session split, initiating a new subsession. We reset important measurements for those subsessions.
After a new subsession split, the internal-telemetry-after-subsession-split
topic is notified to all the observers. This is an internal topic and is only meant for internal Telemetry usage.
Note
saved-session
is sent with a different ping type (saved-session
, not main
), but otherwise has the same format as discussed here.
Structure:
{
version: 4,
info: {
reason: <string>, // what triggered this ping: "saved-session", "environment-change", "shutdown", ...
revision: <string>, // the Histograms.json revision
timezoneOffset: <integer>, // time-zone offset from UTC, in minutes, for the current locale
previousBuildId: <string>, // null if this is the first run, or the previous build ID is unknown
sessionId: <uuid>, // random session id, shared by subsessions
subsessionId: <uuid>, // random subsession id
previousSessionId: <uuid>, // session id of the previous session, null on first run.
previousSubsessionId: <uuid>, // subsession id of the previous subsession (even if it was in a different session),
// null on first run.
subsessionCounter: <unsigned integer>, // the running no. of this subsession since the start of the browser session
profileSubsessionCounter: <unsigned integer>, // the running no. of all subsessions for the whole profile life time
sessionStartDate: <ISO date>, // hourly precision, ISO date in local time
subsessionStartDate: <ISO date>, // hourly precision, ISO date in local time
sessionLength: <integer>, // the session length until now in seconds, monotonic
subsessionLength: <integer>, // the subsession length in seconds, monotonic
flashVersion: <string>, // obsolete, use ``environment.addons.activePlugins``
addons: <string>, // obsolete, use ``environment.addons``
},
processes: {...},
childPayloads: [...], // only present with e10s; reduced payloads from content processes, null on failure
simpleMeasurements: {...},
// The following properties may all be null if we fail to collect them.
histograms: {...},
keyedHistograms: {...},
chromeHangs: {...},
threadHangStats: [...], // obsolete in firefox 57, use the 'bhr' ping
capturedStacks: {...},
log: [...],
webrtc: {...},
gc: {...},
fileIOReports: {...},
lateWrites: {...},
addonDetails: {...},
UIMeasurements: [...], // Android only
slowSQL: {...},
slowSQLstartup: {...},
}
info¶
sessionLength¶
The length of the current session so far in seconds.
This uses a monotonic clock, so this may mismatch with other measurements that
are not monotonic like calculations based on Date.now()
.
If the monotonic clock failed, this will be -1
.
Note that this currently does not behave consistently over our supported platforms:
- On Windows this uses
GetTickCount64()
, which does increase over sleep periods - On macOS this uses
mach_absolute_time()
, which does not increase over sleep periods - On POSIX/Linux this uses
clock_gettime(CLOCK_MONOTONIC, &ts)
, which should not increase over sleep time
See bug 1204823 for details.
subsessionLength¶
The length of this subsession in seconds.
This uses a monotonic clock, so this may mismatch with other measurements that are not monotonic (e.g. based on Date.now()
).
If sessionLength
is -1
, the monotonic clock is not working.
Also see the remarks for sessionLength
on platform consistency.
processes¶
This section contains per-process data.
Structure:
"processes" : {
// ... other processes ...
"parent": {
scalars: {...},
keyedScalars: {...},
events: {...},
},
"content": {
scalars: {...},
keyedScalars: {...},
histograms: {...},
keyedHistograms: {...},
events: {...},
},
"gpu": {
// ...
}
}
histograms and keyedHistograms¶
This section contains histograms and keyed histograms accumulated on content processes. Histograms recorded on a content child process have different character than parent histograms. For instance, GC_MS
will be much different in processes.content
as it has to contend with web content, whereas the instance in payload.histograms
has only to contend with browser JS. Also, some histograms may be absent if never recorded on a content child process (EVENTLOOP_UI_ACTIVITY
is parent-process-only).
This format was adopted in Firefox 51 via bug 1218576.
scalars and keyedScalars¶
This section contains the Scalars that are valid for the current platform. Scalars are only submitted if data was added to them, and are only reported with subsession pings. The recorded scalars are described in the Scalars.yaml file. The info.revision
field indicates the revision of the file that describes the reported scalars.
events¶
This section contains the Events that are recorded for the current subsession. Events are not always recorded, recording has to be enabled first for the Firefox session.
The recorded events are defined in the Events.yaml. The info.revision
field indicates the revision of the file that describes the reported events.
childPayloads¶
The Telemetry payloads sent by child processes, recorded on child process shutdown (event content-child-shutdown
observed). They are reduced session payloads, only available with e10s. Among some other things, they don’t contain histograms, keyed histograms, add-on details, or UI Telemetry.
Note: Child payloads are not collected and cleared with subsession splits, they are currently only meaningful when analysed from saved-session
or main
pings with reason
set to shutdown
.
Note: Before Firefox 51 and bug 1218576, content process histograms and keyedHistograms were in the individual child payloads instead of being aggregated into processes.content
.
simpleMeasurements¶
This section contains a list of simple measurements, or counters. In addition to the ones highlighted below, Telemetry timestamps (see here and here) can be reported.
totalTime¶
A non-monotonic integer representing the number of seconds the session has been alive.
uptime¶
A non-monotonic integer representing the number of minutes the session has been alive.
addonManager¶
Only available in the extended set of measures, it contains a set of counters related to Addons. See here for a list of recorded measures.
UITelemetry¶
Only available in the extended set of measures. For more see UITelemetry data format.
startupInterrupted¶
A boolean set to true if startup was interrupted by an interactive prompt.
js¶
This section contains a series of counters from the JavaScript engine.
Structure:
"js" : {
// ...
}
As of Firefox 59 this section no longer contains any entries.
maximalNumberOfConcurrentThreads¶
An integer representing the highest number of threads encountered so far during the session.
startupSessionRestoreReadBytes¶
Windows-only integer representing the number of bytes read by the main process up until the session store has finished restoring the windows.
startupSessionRestoreWriteBytes¶
Windows-only integer representing the number of bytes written by the main process up until the session store has finished restoring the windows.
startupWindowVisibleReadBytes¶
Windows-only integer representing the number of bytes read by the main process up until after a XUL window is made visible.
startupWindowVisibleWriteBytes¶
Windows-only integer representing the number of bytes written by the main process up until after a XUL window is made visible.
debuggerAttached¶
A boolean set to true if a debugger is attached to the main process.
shutdownDuration¶
The time, in milliseconds, it took to complete the last shutdown.
failedProfileLockCount¶
The number of times the system failed to lock the user profile.
savedPings¶
Integer count of the number of pings that need to be sent.
activeTicks¶
Integer count of the number of five-second intervals (‘ticks’) the user was considered ‘active’ (sending UI events to the window). An extra event is fired immediately when the user becomes active after being inactive. This is for some mouse and gamepad events, and all touch, keyboard, wheel, and pointer events (see EventStateManager.cpp).
This measure might be useful to give a trend of how much a user actually interacts with the browser when compared to overall session duration. It does not take into account whether or not the window has focus or is in the foreground. Just if it is receiving these interaction events.
Note that in main
pings, this measure is reset on subsession splits, while in saved-session
pings it covers the whole browser session.
pingsOverdue¶
Integer count of pending pings that are overdue.
histograms¶
This section contains the histograms that are valid for the current platform. Flag
histograms are always created and submitted with a default value of false
if a value of true
is not recorded during the time period. Other histogram types (see Choosing a Histogram Type) are not created nor submitted if no data was added to them. The type and format of the reported histograms is described by the Histograms.json
file. Its most recent version is available here. The info.revision
field indicates the revision of the file that describes the reported histograms.
keyedHistograms¶
This section contains the keyed histograms available for the current platform.
As of Firefox 48, this section does not contain empty keyed histograms anymore.
threadHangStats¶
As of Firefox 57 this section is no longer present, and has been replaced with the bhr ping.
Contains the statistics about the hangs in main and background threads. Note that hangs in this section capture the C++ pseudostack and an incomplete JS stack, which is not 100% precise. For particularly egregious hangs, and on nightly, an unsymbolicated native stack is also captured. The amount of time that is considered “egregious” is different from thread to thread, and is set when the BackgroundHangMonitor is constructed for that thread. In general though, hangs from 5 - 10 seconds are generally considered egregious. Shorter hangs (1 - 2s) are considered egregious for other threads (the compositor thread, and the hang monitor that is only enabled during tab switch).
To avoid submitting overly large payloads, some limits are applied:
- Identical, adjacent “(chrome script)” or “(content script)” stack entries are collapsed together. If a stack is reduced, the “(reduced stack)” frame marker is added as the oldest frame.
- The depth of the reported pseudostacks is limited to 11 entries. This value represents the 99.9th percentile of the thread hangs stack depths reported by Telemetry.
- The native stacks are limited to a depth of 25 stack frames.
Structure:
"threadHangStats" : [
{
"name" : "Gecko",
"activity" : {...}, // a time histogram of all task run times
"nativeStacks": { // captured for all hangs on nightly, or egregious hangs on beta
"memoryMap": [
["wgdi32.pdb", "08A541B5942242BDB4AEABD8C87E4CFF2"],
["igd10iumd32.pdb", "D36DEBF2E78149B5BE1856B772F1C3991"],
// ... other entries in the format ["module name", "breakpad identifier"] ...
],
"stacks": [
[
[
0, // the module index or -1 for invalid module indices
190649 // the offset of this program counter in its module or an absolute pc
],
[1, 2540075],
// ... other frames ...
],
// ... other stacks ...
]
},
"hangs" : [
{
"stack" : [
"Startup::XRE_Main",
"Timer::Fire",
"(content script)",
"IPDL::PPluginScriptableObject::SendGetChildProperty",
... up to 11 frames ...
],
"nativeStack": 0, // index into nativeStacks.stacks array
"histogram" : {...}, // the time histogram of the hang times
"annotations" : [
{
"pluginName" : "Shockwave Flash",
"pluginVersion" : "18.0.0.209"
},
... other annotations ...
]
},
],
},
... other threads ...
]
capturedStacks¶
Contains information about stacks captured on demand via Telemetry API. For more information see stack capture.
This is similar to chromeHangs, but only Precise C++ stacks on the main thread of
the parent process are reported. This data is only available on Windows, either
in Firefox Nightly or in builds using --enable-profiling
switch.
Limits for captured stacks are the same as for chromeHangs (see below). Furthermore:
- the key length is limited to 50 characters,
- keys are restricted to alpha-numeric characters and -.
The module names can contain unicode characters.
Structure:
"capturedStacks" : {
"memoryMap": [
["wgdi32.pdb", "08A541B5942242BDB4AEABD8C87E4CFF2"],
["igd10iumd32.pdb", "D36DEBF2E78149B5BE1856B772F1C3991"],
// ... other entries in the format ["module name", "breakpad identifier"] ...
],
"stacks": [
[
[
0, // the module index or -1 for invalid module indices
190649 // the offset of this program counter in its module or an absolute pc
],
[1, 2540075],
// ... other frames ...
],
// ... other stacks ...
],
"captures": [["string-key", stack-index, count], ... ]
}
chromeHangs¶
Contains the statistics about the hangs happening exclusively on the main thread of the parent process. Precise C++ stacks are reported. This is only available on Nightly Release on Windows, when building using “–enable-profiling” switch.
Some limits are applied:
- Reported chrome hang stacks are limited in depth to 50 entries.
- The maximum number of reported stacks is 50.
The module names can contain unicode characters.
Structure:
"chromeHangs" : {
"memoryMap" : [
["wgdi32.pdb", "08A541B5942242BDB4AEABD8C87E4CFF2"],
["igd10iumd32.pdb", "D36DEBF2E78149B5BE1856B772F1C3991"],
... other entries in the format ["module name", "breakpad identifier"] ...
],
"stacks" : [
[
[
0, // the module index or -1 for invalid module indices
190649 // the offset of this program counter in its module or an absolute pc
],
[1, 2540075],
... other frames, up to 50 ...
],
... other stacks, up to 50 ...
],
"durations" : [8, ...], // the hang durations (in seconds)
"systemUptime" : [692, ...], // the system uptime (in minutes) at the time of the hang
"firefoxUptime" : [672, ...], // the Firefox uptime (in minutes) at the time of the hang
"annotations" : [
[
[0, ...], // the indices of the related hangs
{
"pluginName" : "Shockwave Flash",
"pluginVersion" : "18.0.0.209",
... other annotations as key:value pairs ...
}
],
...
]
},
log¶
This section contains a log of important or unusual events reported through Telemetry.
Structure:
"log": [
[
"Event_ID",
3785, // the timestamp (in milliseconds) for the log entry
... other data ...
],
...
]
At present there is one known users of this section: Telemetry Experiments.
Telemetry Experiments uses it to note when experiments are activated and terminated.
webrtc¶
Contains special statistics gathered by WebRTC related components.
So far only a bitmask for the ICE candidate type present in a successful or failed WebRTC connection is getting reported through C++ code as IceCandidatesStats, because the required bitmask is too big to be represented in a regular enum histogram.
Note: in most cases the webrtc dictionary inside of IceCandidatesStats will simply be empty as the user has not used any WebRTC PeerConnection at all during the ping report time.
Structure:
"webrtc": {
"IceCandidatesStats": {
"webrtc": {
"34526345": {
"successCount": 5
},
"2354353": {
"failureCount": 1
}
},
}
},
gc¶
Contains statistics about selected garbage collections. To avoid bloating the ping, only a few GCs are included. There are two selection strategies. We always save the two GCs with the worst max_pause time. Additionally, in content processes, two collections are selected at random. If a GC runs for C milliseconds and the total time for all GCs since the session began is T milliseconds, then the GC has a C/T probablility of being selected for one of these “slots”.
Structure:
"gc": {
"random": [
{
// "completed" or "aborted" if an OOM occured.
"status": "completed",
// Timestamps are in milliseconds since startup. All the times here
// are wall-clock times, which may not be monotonically increasing.
"timestamp": 294872.2,
// All durations are in milliseconds.
"max_pause": 73.629,
"total_time": 364.951, // Sum of all slice times.
"zones_collected": 9,
"total_zones": 9,
"total_compartments": 309,
"minor_gcs": 44,
// Present if non-zero.
"store_buffer_overflows": 19,
"mmu_20ms": 0,
"mmu_50ms": 0,
// Reasons include "None", "NonIncrementalRequested",
// "AbortRequested", "KeepAtomsSet", "IncrementalDisabled",
// "ModeChange", "MallocBytesTrigger", "GCBytesTrigger",
// "ZoneChange", "CompartmentRevived".
// Present for non-incremental GCs only.
"nonincremental_reason": "GCBytesTrigger",
"allocated_bytes": 38853696 // in bytes
// Present if non-zero.
"added_chunks": 54,
"removed_chunks": 12,
// Total number of slices (some of which may not appear
// in the "slices" array).
"slices": 15,
// We record at most 4 slices.
"slice_number": 218, // The first slice number for this GC event.
"slices_list": [
{
"slice": 218, // The global index of this slice.
"pause": 23.221, // How long the slice took (milliseconds).
"reason": "SET_NEW_DOCUMENT",
// GC state when the slice started
"initial_state": "NotActive",
// GC state when the slice ended
"final_state": "Mark",
// Budget is either "Xms", "work(Y)", or
// "unlimited".
"budget": "10ms",
// Number of page faults during the slice.
// optional field, missing means 0.
"page_faults": 1,
// The start time of this slice in seconds. The end time is
// given by the start_timestamp + pause.
"start_timestamp": 294875,
// Time taken by each phase. There are at most 65 possible
// phases, but usually only a few phases run in a given slice.
"times": {
"wait_background_thread": 0.012,
"mark_discard_code": 2.845,
"purge": 0.723,
"mark": 9.831,
"mark_roots": 0.102,
"buffer_gray_roots": 3.095,
"mark_cross_compartment_wrappers": 0.039,
"mark_c_and_js_stacks": 0.005,
"mark_runtime_wide_data": 2.313,
"mark_embedding": 0.117,
"mark_compartments": 2.27,
"unmark": 1.063,
"minor_gcs_to_evict_nursery": 8.701,
...
}
},
{ ... },
],
// Sum of the phase times across all slices, including
// omitted slices. As before, there are <= 65 possible phases.
"totals": {
"wait_background_thread": 0.012,
"mark_discard_code": 2.845,
"purge": 0.723,
"mark": 9.831,
"mark_roots": 0.102,
"buffer_gray_roots": 3.095,
"mark_cross_compartment_wrappers": 0.039,
"mark_c_and_js_stacks": 0.005,
"mark_runtime_wide_data": 2.313,
"mark_embedding": 0.117,
"mark_compartments": 2.27,
"unmark": 1.063,
"minor_gcs_to_evict_nursery": 8.701,
...
}
},
... // Up to four more selected GCs follow.
],
"worst": [
... // Same as above, but the 2 worst GCs by max_pause.
]
},
fileIOReports¶
Contains the statistics of main-thread I/O recorded during the execution. Only the I/O stats for the XRE and the profile directories are currently reported, neither of them disclosing the full local path.
Structure:
"fileIOReports": {
"{xre}": [
totalTime, // Accumulated duration of all operations
creates, // Number of create/open operations
reads, // Number of read operations
writes, // Number of write operations
fsyncs, // Number of fsync operations
stats, // Number of stat operations
],
"{profile}": [ ... ],
...
}
lateWrites¶
This sections reports writes to the file system that happen during shutdown. The reported data contains the stack and the file names of the loaded libraries at the time the writes happened.
The file names of the loaded libraries can contain unicode characters.
Structure:
"lateWrites" : {
"memoryMap" : [
["wgdi32.pdb", "08A541B5942242BDB4AEABD8C87E4CFF2"],
... other entries in the format ["module name", "breakpad identifier"] ...
],
"stacks" : [
[
[
0, // the module index or -1 for invalid module indices
190649 // the offset of this program counter in its module or an absolute pc
],
[1, 2540075],
... other frames ...
],
... other stacks ...
],
},
addonDetails¶
This section contains per add-on telemetry details, as reported by each add-on provider. The XPI provider is the only one reporting at the time of writing (see DXR). Telemetry does not manipulate or enforce a specific format for the supplied provider’s data.
Structure:
"addonDetails": {
"XPI": {
"adbhelper@mozilla.org": {
"scan_items": 24,
"scan_MS": 3,
"location": "app-profile",
"name": "ADB Helper",
"creator": "Mozilla & Android Open Source Project",
"startup_MS": 30
},
...
},
...
}
UITelemetry¶
See the UITelemetry data format
documentation.
slowSQL¶
This section contains the informations about the slow SQL queries for both the main and other threads. The execution of an SQL statement is considered slow if it takes 50ms or more on the main thread or 100ms or more on other threads. Slow SQL statements will be automatically trimmed to 1000 characters. This limit doesn’t include the ellipsis and database name, that are appended at the end of the stored statement.
Structure:
"slowSQL": {
"mainThread": {
"Sanitized SQL Statement": [
1, // the number of times this statement was hit
200 // the total time (in milliseconds) that was spent on this statement
],
...
},
"otherThreads": {
"VACUUM /* places.sqlite */": [
1,
330
],
...
}
},
slowSQLStartup¶
This section contains the slow SQL statements gathered at startup (until the “sessionstore-windows-restored” event is fired). The structure of this section resembles the one for slowSQL.
UIMeasurements¶
This section is Android-only and contains UI specific Telemetry measurements and events (see here).
Structure:
"UIMeasurements": [
{
"type": "event", // either "session" or "event"
"action": "action.1",
"method": "menu",
"sessions": [],
"timestamp": 12345,
"extras": "settings"
},
{
"type": "session",
"name": "awesomescreen.1",
"reason": "commit",
"start": 123,
"end": 456
}
...
],