Bug 1621402 - Add telemetry to capture failures to read attribution data r=janerik,mixedpuppy

Differential Revision: https://phabricator.services.mozilla.com/D67163

--HG--
extra : moz-landing-system : lando

browser/components/attribution/AttributionCode.jsm

@@ -80,7 +80,16 @@ var AttributionCode = {
         break;
       }
     }
-    return isValid ? parsed : {};
+
+    if (isValid) {
+      return parsed;
+    }
+
+    Services.telemetry
+      .getHistogramById("BROWSER_ATTRIBUTION_ERRORS")
+      .add("decode_error");
+
+    return {};
   },
 
   /**
@@ -100,15 +109,28 @@ var AttributionCode = {
 
     gCachedAttrData = {};
     if (AppConstants.platform == "win") {
+      let bytes;
       try {
-        let bytes = await OS.File.read(getAttributionFile().path);
-        let decoder = new TextDecoder();
-        let code = decoder.decode(bytes);
-        gCachedAttrData = this.parseAttributionCode(code);
+        bytes = await OS.File.read(getAttributionFile().path);
       } catch (ex) {
-        // The attribution file may already have been deleted,
-        // or it may have never been installed at all;
-        // failure to open or read it isn't an error.
+        if (ex instanceof OS.File.Error && ex.becauseNoSuchFile) {
+          return gCachedAttrData;
+        }
+        Services.telemetry
+          .getHistogramById("BROWSER_ATTRIBUTION_ERRORS")
+          .add("read_error");
+      }
+      if (bytes) {
+        try {
+          let decoder = new TextDecoder();
+          let code = decoder.decode(bytes);
+          gCachedAttrData = this.parseAttributionCode(code);
+        } catch (ex) {
+          // TextDecoder can throw an error
+          Services.telemetry
+            .getHistogramById("BROWSER_ATTRIBUTION_ERRORS")
+            .add("decode_error");
+        }
       }
     } else if (AppConstants.platform == "macosx") {
       try {

browser/components/attribution/moz.build

@@ -9,6 +9,8 @@ with Files("**"):
 
 XPCSHELL_TESTS_MANIFESTS += ['test/xpcshell/xpcshell.ini']
 
+BROWSER_CHROME_MANIFESTS += ['test/browser/browser.ini']
+
 EXTRA_JS_MODULES += [
     'AttributionCode.jsm',
 ]

browser/components/attribution/test/browser/browser.ini

@@ -0,0 +1,4 @@
+[DEFAULT]
+
+[browser_AttributionCode_telemetry.js]
+skip-if = os != "win" # Windows only telemetry

browser/components/attribution/test/browser/browser_AttributionCode_telemetry.js

@@ -0,0 +1,97 @@
+ChromeUtils.defineModuleGetter(
+  this,
+  "TelemetryTestUtils",
+  "resource://testing-common/TelemetryTestUtils.jsm"
+);
+const { AttributionCode } = ChromeUtils.import(
+  "resource:///modules/AttributionCode.jsm"
+);
+ChromeUtils.defineModuleGetter(this, "OS", "resource://gre/modules/osfile.jsm");
+const { sinon } = ChromeUtils.import("resource://testing-common/Sinon.jsm");
+
+async function writeAttributionFile(data) {
+  let appDir = Services.dirsvc.get("LocalAppData", Ci.nsIFile);
+  let file = appDir.clone();
+  file.append(Services.appinfo.vendor || "mozilla");
+  file.append(AppConstants.MOZ_APP_NAME);
+
+  await OS.File.makeDir(file.path, { from: appDir.path, ignoreExisting: true });
+
+  file.append("postSigningData");
+  await OS.File.writeAtomic(file.path, data);
+}
+
+add_task(function setup() {
+  // Clear cache call is only possible in a testing environment
+  let env = Cc["@mozilla.org/process/environment;1"].getService(
+    Ci.nsIEnvironment
+  );
+  env.set("XPCSHELL_TEST_PROFILE_DIR", "testing");
+
+  registerCleanupFunction(() => {
+    env.set("XPCSHELL_TEST_PROFILE_DIR", null);
+  });
+});
+
+add_task(async function test_parse_error() {
+  registerCleanupFunction(async () => {
+    await AttributionCode.deleteFileAsync();
+    AttributionCode._clearCache();
+  });
+  const histogram = Services.telemetry.getHistogramById(
+    "BROWSER_ATTRIBUTION_ERRORS"
+  );
+  // Delete the file to trigger a read error
+  await AttributionCode.deleteFileAsync();
+  AttributionCode._clearCache();
+  // Clear any existing telemetry
+  histogram.clear();
+  let result = await AttributionCode.getAttrDataAsync();
+  Assert.deepEqual(
+    result,
+    {},
+    "Shouldn't be able to get a result if the file doesn't exist"
+  );
+
+  // Write an invalid file to trigger a decode error
+  await AttributionCode.deleteFileAsync();
+  AttributionCode._clearCache();
+  await writeAttributionFile(""); // empty string is invalid
+  result = await AttributionCode.getAttrDataAsync();
+  Assert.deepEqual(result, {}, "Should have failed to parse");
+
+  // `assertHistogram` also ensures that `read_error` index 0 is 0
+  // as we should not have recorded telemetry from the previous `getAttrDataAsync` call
+  TelemetryTestUtils.assertHistogram(histogram, 1, 1);
+  // Reset
+  histogram.clear();
+});
+
+add_task(async function test_read_error() {
+  registerCleanupFunction(async () => {
+    await AttributionCode.deleteFileAsync();
+    AttributionCode._clearCache();
+  });
+  const histogram = Services.telemetry.getHistogramById(
+    "BROWSER_ATTRIBUTION_ERRORS"
+  );
+  const sandbox = sinon.createSandbox();
+  // Delete the file to trigger a read error
+  await AttributionCode.deleteFileAsync();
+  AttributionCode._clearCache();
+  // Clear any existing telemetry
+  histogram.clear();
+
+  // Force a read error
+  const stub = sandbox.stub(OS.File, "read");
+  stub.throws(() => new Error("read_error"));
+  // Try to read the file
+  await AttributionCode.getAttrDataAsync();
+
+  // It should record the read error
+  TelemetryTestUtils.assertHistogram(histogram, 0, 1);
+
+  // Clear any existing telemetry
+  histogram.clear();
+  sandbox.restore();
+});

toolkit/components/telemetry/Histograms.json

@@ -10728,6 +10728,18 @@
     "kind": "boolean",
     "description": "The result of the default browser check for assist intent."
   },
+  "BROWSER_ATTRIBUTION_ERRORS": {
+    "record_in_processes": ["main", "content"],
+    "products": ["firefox"],
+    "expires_in_version": "80",
+    "kind": "categorical",
+    "labels": ["read_error", "decode_error"],
+    "description": "Count for the number of errors encountered trying to read the attribution data from the stub installer.",
+    "releaseChannelCollection": "opt-out",
+    "bug_numbers": [1621402],
+    "alert_emails": ["aoprea@mozilla.com"],
+    "operating_systems": ["windows"]
+  },
   "MIXED_CONTENT_PAGE_LOAD": {
     "record_in_processes": ["main", "content"],
     "products": ["firefox", "fennec", "geckoview"],