Bug 1848542 - Add telemetry for residual cache folder removal or failure r=necko-reviewers,kershaw

Differential Revision: https://phabricator.services.mozilla.com/D194076

netwerk/cache2/CacheFileIOManager.cpp

@@ -34,6 +34,7 @@
 #include "mozilla/IntegerPrintfMacros.h"
 #include "mozilla/Preferences.h"
 #include "nsNetUtil.h"
+#include "mozilla/glean/GleanMetrics.h"
 
 #ifdef MOZ_BACKGROUNDTASKS
 #  include "mozilla/BackgroundTasksRunner.h"
@@ -1462,7 +1463,17 @@ nsresult CacheFileIOManager::OnIdleDaily() {
                 continue;
               }
               if (leafName.Find(kPurgeExtension) != kNotFound) {
-                subdir->Remove(true);
+                mozilla::glean::networking::residual_cache_folder_count.Add(1);
+                rv = subdir->Remove(true);
+                if (NS_SUCCEEDED(rv)) {
+                  mozilla::glean::networking::residual_cache_folder_removal
+                      .Get("success"_ns)
+                      .Add(1);
+                } else {
+                  mozilla::glean::networking::residual_cache_folder_removal
+                      .Get("failure"_ns)
+                      .Add(1);
+                }
               }
             }
 

netwerk/metrics.yaml

@@ -402,3 +402,32 @@ networking:
       - acreskey@mozilla.com
     expires: never
     telemetry_mirror: HTTP_UPLOAD_THROUGHPUT_MBPS_HTTP_3
+
+  residual_cache_folder_count:
+    type: counter
+    description: >
+      Counts how often we find a cache folder that wasn't purged
+      at shutdown by a background task process.
+    bugs:
+      - https://bugzilla.mozilla.org/1848542
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1848542
+    notification_emails:
+      - vgosu@mozilla.com
+    expires: 136
+
+  residual_cache_folder_removal:
+    type: labeled_counter
+    description: >
+      Counts how often succeed/fail in removing cache folder
+      that wasn't purged at shutdown
+    bugs:
+      - https://bugzilla.mozilla.org/1848542
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1848542
+    notification_emails:
+      - vgosu@mozilla.com
+    expires: 136
+    labels:
+      - success
+      - failure

netwerk/test/browser/browser_purgeCache_idle_daily.js

@@ -5,6 +5,7 @@
 "use strict";
 
 add_task(async function test_idle_cleanup() {
+  Services.fog.testResetFOG();
   Services.prefs.setBoolPref(
     "network.cache.shutdown_purge_in_background_task",
     true
@@ -32,6 +33,51 @@ add_task(async function test_idle_cleanup() {
     false,
     `Folder ${dir.path} should have been purged by background task`
   );
+  Assert.equal(
+    await Glean.networking.residualCacheFolderCount.testGetValue(),
+    1
+  );
+  Assert.equal(
+    await Glean.networking.residualCacheFolderRemoval.success.testGetValue(),
+    1
+  );
+  Assert.equal(
+    await Glean.networking.residualCacheFolderRemoval.failure.testGetValue(),
+    null
+  );
+
+  // Check that telemetry properly detects folders failing to be deleted when readonly
+  // Making folders readonly only works on windows
+  if (AppConstants.platform == "win") {
+    dir.create(Ci.nsIFile.DIRECTORY_TYPE, 0o744);
+    dir.QueryInterface(Ci.nsILocalFileWin).readOnly = true;
+
+    Services.obs.notifyObservers(null, "idle-daily");
+
+    await BrowserTestUtils.waitForCondition(async () => {
+      return (
+        (await Glean.networking.residualCacheFolderRemoval.failure.testGetValue()) ==
+        1
+      );
+    });
+
+    Assert.equal(
+      await Glean.networking.residualCacheFolderCount.testGetValue(),
+      2
+    );
+    Assert.equal(
+      await Glean.networking.residualCacheFolderRemoval.success.testGetValue(),
+      1
+    );
+    Assert.equal(
+      await Glean.networking.residualCacheFolderRemoval.failure.testGetValue(),
+      1
+    );
+
+    dir.QueryInterface(Ci.nsILocalFileWin).readOnly = false;
+    dir.remove(true);
+  }
+
   Services.prefs.clearUserPref(
     "network.cache.shutdown_purge_in_background_task"
   );