Bug 1319286 - Cache nsIUrlClassifierDBService.getTables result until next update. r=francois.

MozReview-Commit-ID: ItjTQNzCVED

toolkit/components/url-classifier/Classifier.cpp

@@ -22,6 +22,7 @@
 #include "mozilla/Unused.h"
 #include "mozilla/TypedEnumBits.h"
 #include "nsIUrlClassifierUtils.h"
+#include "nsUrlClassifierDBService.h"
 
 // MOZ_LOG=UrlClassifierDbService:5
 extern mozilla::LazyLogModule gUrlClassifierDbServiceLog;
@@ -144,6 +145,7 @@ Classifier::GetPrivateStoreDirectory(nsIFile* aRootStoreDirectory,
 }
 
 Classifier::Classifier()
+  : mIsTableRequestResultOutdated(true)
 {
 }
 
@@ -348,6 +350,16 @@ Classifier::AbortUpdateAndReset(const nsCString& aTable)
 void
 Classifier::TableRequest(nsACString& aResult)
 {
+  MOZ_ASSERT(!NS_IsMainThread(),
+             "TableRequest must be called on the classifier worker thread.");
+
+  // This function and all disk I/O are guaranteed to occur
+  // on the same thread so we don't need to add a lock around.
+  if (!mIsTableRequestResultOutdated) {
+    aResult = mTableRequestResult;
+    return;
+  }
+
   // Generating v2 table info.
   nsTArray<nsCString> tables;
   ActiveTables(tables);
@@ -387,8 +399,13 @@ Classifier::TableRequest(nsACString& aResult)
   // Specifically for v4 tables.
   nsCString metadata;
   nsresult rv = LoadMetadata(mRootStoreDirectory, metadata);
-  NS_ENSURE_SUCCESS_VOID(rv);
-  aResult.Append(metadata);
+  if (NS_SUCCEEDED(rv)) {
+    aResult.Append(metadata);
+  }
+
+  // Update the TableRequest result in-memory cache.
+  mTableRequestResult = aResult;
+  mIsTableRequestResultOutdated = false;
 }
 
 // This is used to record the matching statistics for v2 and v4.
@@ -534,6 +551,10 @@ Classifier::ApplyUpdates(nsTArray<TableUpdate*>* aUpdates)
           rv = UpdateTableV4(aUpdates, updateTable);
         }
 
+        // We mark the table associated info outdated no matter the
+        // update is successful to avoid any possibile non-atomic update.
+        mIsTableRequestResultOutdated = true;
+
         if (NS_FAILED(rv)) {
           if (rv != NS_ERROR_OUT_OF_MEMORY) {
 #ifdef MOZ_SAFEBROWSING_DUMP_FAILED_UPDATES
@@ -1009,6 +1030,9 @@ nsresult
 Classifier::UpdateTableV4(nsTArray<TableUpdate*>* aUpdates,
                           const nsACString& aTable)
 {
+  MOZ_ASSERT(!NS_IsMainThread(),
+             "UpdateTableV4 must be called on the classifier worker thread.");
+
   LOG(("Classifier::UpdateTableV4(%s)", PromiseFlatCString(aTable).get()));
 
   if (!CheckValidUpdate(aUpdates, aTable)) {

toolkit/components/url-classifier/Classifier.h

@@ -159,6 +159,14 @@ private:
   uint32_t mHashKey;
   // Stores the last time a given table was updated (seconds).
   nsDataHashtable<nsCStringHashKey, int64_t> mTableFreshness;
+
+  // In-memory cache for the result of TableRequest. See
+  // nsIUrlClassifierDBService.getTables for the format.
+  nsCString mTableRequestResult;
+
+  // Whether mTableRequestResult is outdated and needs to
+  // be reloaded from disk.
+  bool mIsTableRequestResultOutdated;
 };
 
 } // namespace safebrowsing

toolkit/components/url-classifier/tests/unit/test_listmanager.js

@@ -360,7 +360,17 @@ function waitUntilMetaDataSaved(expectedState, expectedChecksum, callback) {
       if (stateBase64 === btoa(expectedState) &&
           checksumBase64 === btoa(expectedChecksum)) {
         do_print('State has been saved to disk!');
-        callback();
+
+        // We slightly defer the callback to see if the in-memory
+        // |getTables| caching works correctly.
+        dbService.getTables(cachedMetadata => {
+          equal(cachedMetadata, metaData);
+          callback();
+        });
+
+        // Even though we haven't done callback at this moment
+        // but we still claim "we have" in order to stop repeating
+        // a new timer.
         didCallback = true;
       }