Bug 1380081 - Part 13: Add telemetry documentation for the new ping format, r=bsmedberg, r=froydnj

MozReview-Commit-ID: G4hFZcR2EGL

toolkit/components/telemetry/docs/data/backgroundhangmonitor-ping.rst

@@ -0,0 +1,118 @@
+
+"backgroundhangmonitor" ping
+==========
+
+Whenever a thread monitored by the Background Hang Monitor hangs, a stack and
+some non-identifying information about the hang is captured. When 50 of these
+hangs are collected across all processes, or the browser exits, this ping is
+transmitted with the collected hang information.
+
+This ping is only collected in nightly builds, to avoid the high volume of pings
+which would be produced in Beta.
+
+Structure:
+
+.. code-block:: js
+
+    {
+      "type": "backgroundhangmonitor",
+      ... // common ping data
+      "environment": { ... },
+      "payload": {
+        "modules": [
+          [
+            <string>, // Name of the file holding the debug information.
+            <string> // Breakpad ID of this module.
+          ],
+          ...
+        ],
+        "hangs": [
+          {
+            "duration": <number>, // duration of the hang in milliseconds.
+            "thread": <string>, // name of the hanging thread.
+            "runnableName": <string>, // name of the runnable executing during the hang.
+                                      // Runnable names are only collected for the XPCOM main thread.
+            "process": <string>, // Type of process that hung, see below for a list of types.
+            "annotations": { ... }, // A set of annotations on the hang, see below.
+            "pseudoStack": [ ... ], // List of pseudostack frame names.
+            "stack": [ ... ], // interleaved hang stack, see below.
+          },
+          ...
+        ]
+      }
+    }
+
+.. note: :
+
+  Hangs are collected whenever the current runnable takes over 128ms.
+
+Process Types
+-------------
+
+The ``process`` field is a string denoting the kind of process that hung. Hangs
+are currently sent only for the processes below:
+
++---------------+---------------------------------------------------+
+| Kind          | Description                                       |
++===============+===================================================+
+| default       | Main process, also known as the browser process   |
++---------------+---------------------------------------------------+
+| tab           | Content process                                   |
++---------------+---------------------------------------------------+
+| gpu           | GPU process                                       |
++---------------+---------------------------------------------------+
+
+Stack Traces
+------------
+
+Each hang object contains a ``stack`` field which has been populated with an
+interleaved stack trace of the hung thread. An interleaved stack consists of a
+native backtrace with additional frames interleaved, representing chrome JS and
+pseudostack entries.
+
+Note that this field only contains native stack frames, pseudostack and chrome
+JS script frames. If native stacks can not be collected on the target platform,
+or stackwalking was not initialized, there will be no native frames present, and
+the stack will consist only of pseudostack and chrome JS script frames.
+
+A single frame in the stack is either a raw string, representing a pseudostack
+or chrome JS script frame, or a native stack frame:
+
+.. code-block:: js
+
+    [
+      <number>, // Index in the payload.modules list of the module description.
+                // -1 if this frame was not in a valid module.
+      <string> // Hex string (e.g. "FF0F") of the frame offset in the module.
+    ]
+
+Annotations
+-----------
+
+The annotations field is a map from key to string value, for example if the user
+was interacting during a hang the annotations field would look something like
+this:
+
+.. code-block:: js
+
+    {
+        "UserInteracting": "true"
+    }
+
+The following annotations are currently present in tree:
+
++-----------------+-------------------------------------------------+
+| Name            | Description                                     |
++=================+=================================================+
+| UserInteracting | "true" if the user was actively interacting     |
++-----------------+-------------------------------------------------+
+| pluginName      | Name of the currently running plugin            |
++-----------------+-------------------------------------------------+
+| pluginVersion   | Version of the currently running plugin         |
++-----------------+-------------------------------------------------+
+| HangUIShown     | "true" if the hang UI was shown                 |
++-----------------+-------------------------------------------------+
+| HangUIContinued | "true" if continue was selected in the hang UI  |
++-----------------+-------------------------------------------------+
+| HangUIDontShow  | "true" if the hang UI was not shown             |
++-----------------+-------------------------------------------------+

toolkit/components/telemetry/docs/data/index.rst

@@ -12,6 +12,7 @@ Data documentation
    main-ping
    deletion-ping
    crash-ping
+   backgroundhangmonitor-ping
    anonymous-ping
    *-ping