Bug 1161515 - Add previousSessionId to Telemetry payloads. r=gfritzsche

toolkit/components/telemetry/TelemetrySession.jsm

@@ -744,6 +744,7 @@ this.TelemetrySession = Object.freeze({
   reset: function() {
     Impl._sessionId = null;
     Impl._subsessionId = null;
+    Impl._previousSessionId = null;
     Impl._previousSubsessionId = null;
     Impl._subsessionCounter = 0;
     Impl._profileSubsessionCounter = 0;
@@ -816,6 +817,8 @@ let Impl = {
   _sessionId: null,
   // Random subsession id.
   _subsessionId: null,
+  // Session id of the previous session, null on first run.
+  _previousSessionId: null,
   // Subsession id of the previous subsession (even if it was in a different session),
   // null on first run.
   _previousSubsessionId: null,
@@ -1122,6 +1125,7 @@ let Impl = {
 
       sessionId: this._sessionId,
       subsessionId: this._subsessionId,
+      previousSessionId: this._previousSessionId,
       previousSubsessionId: this._previousSubsessionId,
 
       subsessionCounter: this._subsessionCounter,
@@ -1916,13 +1920,14 @@ let Impl = {
     let dataFile = OS.Path.join(OS.Constants.Path.profileDir, DATAREPORTING_DIRECTORY,
                                 SESSION_STATE_FILE_NAME);
 
-    // Try to load the "profileSubsessionCounter" from the state file.
+    // Try to load info about the previous session from the state file.
     try {
       let data = yield CommonUtils.readJSON(dataFile);
       if (data &&
           "profileSubsessionCounter" in data &&
           typeof(data.profileSubsessionCounter) == "number" &&
-          "subsessionId" in data) {
+          "subsessionId" in data && "sessionId" in data) {
+        this._previousSessionId = data.sessionId;
         this._previousSubsessionId = data.subsessionId;
         // Add |_subsessionCounter| to the |_profileSubsessionCounter| to account for
         // new subsession while loading still takes place. This will always be exactly
@@ -1942,6 +1947,7 @@ let Impl = {
    */
   _getSessionDataObject: function() {
     return {
+      sessionId: this._sessionId,
       subsessionId: this._subsessionId,
       profileSubsessionCounter: this._profileSubsessionCounter,
     };

toolkit/components/telemetry/docs/main-ping.rst

@@ -30,6 +30,7 @@ Structure::
 
         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.
 

toolkit/components/telemetry/tests/unit/test_SubsessionChaining.js

@@ -42,6 +42,8 @@ let promiseValidateArchivedPings = Task.async(function*(aExpectedReasons) {
   let previousPing = yield TelemetryArchive.promiseArchivedPingById(list[0].id);
   Assert.equal(aExpectedReasons.shift(), previousPing.payload.info.reason,
                "Telemetry should only get pings with expected reasons.");
+  Assert.equal(previousPing.payload.info.previousSessionId, null,
+               "The first session must report a null previous session id.");
   Assert.equal(previousPing.payload.info.previousSubsessionId, null,
                "The first subsession must report a null previous subsession id.");
   Assert.equal(previousPing.payload.info.profileSubsessionCounter, 1,
@@ -50,6 +52,7 @@ let promiseValidateArchivedPings = Task.async(function*(aExpectedReasons) {
                "subsessionCounter must be 1 the first time.");
 
   let expectedSubsessionCounter = 1;
+  let expectedPreviousSessionId = previousPing.payload.info.sessionId;
 
   for (let i = 1; i < list.length; i++) {
     let currentPing = yield TelemetryArchive.promiseArchivedPingById(list[i].id);
@@ -59,6 +62,8 @@ let promiseValidateArchivedPings = Task.async(function*(aExpectedReasons) {
 
     Assert.equal(aExpectedReasons.shift(), currentInfo.reason,
                  "Telemetry should only get pings with expected reasons.");
+    Assert.equal(currentInfo.previousSessionId, expectedPreviousSessionId,
+                 "Telemetry must correctly chain session identifiers.");
     Assert.equal(currentInfo.previousSubsessionId, previousInfo.subsessionId,
                  "Telemetry must correctly chain subsession identifiers.");
     Assert.equal(currentInfo.profileSubsessionCounter, previousInfo.profileSubsessionCounter + 1,
@@ -70,8 +75,13 @@ let promiseValidateArchivedPings = Task.async(function*(aExpectedReasons) {
     previousPing = currentPing;
     // Reset the expected subsession counter, if required. Otherwise increment the expected
     // subsession counter.
-    expectedSubsessionCounter =
-      SESSION_END_PING_REASONS.has(currentInfo.reason) ? 1 : (expectedSubsessionCounter + 1);
+    // If this is the final subsession of a session we need to update expected values accordingly.
+    if (SESSION_END_PING_REASONS.has(currentInfo.reason)) {
+      expectedSubsessionCounter = 1;
+      expectedPreviousSessionId = currentInfo.sessionId;
+    } else {
+      expectedSubsessionCounter++;
+    }
   }
 });
 

toolkit/components/telemetry/tests/unit/test_TelemetrySession.js

@@ -1167,6 +1167,7 @@ add_task(function* test_savedSessionData() {
   // Write test data to the session data file.
   const dataFilePath = OS.Path.join(DATAREPORTING_PATH, "session-state.json");
   const sessionState = {
+    sessionId: null,
     subsessionId: null,
     profileSubsessionCounter: 3785,
   };