leveldb: Add DBTracker for exposing databases to Chrome's memory-infra.

third_party/leveldatabase/env_chromium_unittest.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "third_party/leveldatabase/env_chromium.h"
 #include "base/files/file.h"
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/lazy_instance.h"
+#include "base/macros.h"
 #include "base/test/test_suite.h"
 #include "testing/gtest/include/gtest/gtest.h"
-#include "third_party/leveldatabase/env_chromium.h"
 #include "third_party/leveldatabase/src/include/leveldb/db.h"
 
 #define FPL FILE_PATH_LITERAL
 
 using leveldb::DB;
 using leveldb::Env;
 using leveldb::Options;
 using leveldb::ReadOptions;
 using leveldb::Slice;
 using leveldb::Status;
@@ skipping 159 matching lines @@
   // The disk size equating to the max buffer size
   EXPECT_EQ(size_t(4 * MB), leveldb_env::WriteBufferSize(40 * MB));
 
   // Make sure sizes larger than 40MB are clamped to max buffer size.
   EXPECT_EQ(size_t(4 * MB), leveldb_env::WriteBufferSize(80 * MB));
 
   // Check for very large disk size (catch overflow).
   EXPECT_EQ(size_t(4 * MB), leveldb_env::WriteBufferSize(100 * MB * MB));
 }
 
+TEST(ChromiumEnv, DBRegistryOpen) {

[pwnall, 2017/06/22 02:50:22]

Thank you for tests!

FYI, leveldb tests don't run on the CQ yet. Please make sure they pass on your
machine.

ninja -C out/Default/ leveldb_env_test
out/Default/leveldb_env_test

[DmitrySkiba, 2017/06/26 20:45:19]

Acknowledged.

+  base::ScopedTempDir scoped_temp_dir;
+  ASSERT_TRUE(scoped_temp_dir.CreateUniqueTempDir());
+  base::FilePath dir = scoped_temp_dir.GetPath();
+
+  struct KeyValue {
+    const char* key;
+    const char* value;
+  };
+  constexpr KeyValue db_data[] = {
+      {"banana", "yellow"}, {"sky", "blue"}, {"enthusiasm", ""},
+  };
+
+  // Open a new database using DBRegistry::Open, write some data

[pwnall, 2017/06/22 02:50:22]

Periods at the end of sentences?

[DmitrySkiba, 2017/06/26 20:45:19]

Done.

+  Options options;
+  options.create_if_missing = true;
+  DB* db;
+  Status status =
+      leveldb_env::DBRegistry::Open(options, dir.AsUTF8Unsafe(), &db);
+  ASSERT_TRUE(status.ok()) << status.ToString();
+  for (const auto& kv : db_data) {
+    status = db->Put(WriteOptions(), kv.key, kv.value);
+    ASSERT_TRUE(status.ok()) << status.ToString();
+  }
+
+  // Close the database
+  delete db;
+
+  // Open the database again with DB::Open, and check the data
+  options.create_if_missing = false;
+  status = leveldb::DB::Open(options, dir.AsUTF8Unsafe(), &db);
+  ASSERT_TRUE(status.ok()) << status.ToString();
+  for (const auto& kv : db_data) {
+    std::string value;
+    status = db->Get(ReadOptions(), kv.key, &value);
+    ASSERT_TRUE(status.ok()) << status.ToString();
+    ASSERT_EQ(value, kv.value);
+  }
+  delete db;
+}
+
+TEST(ChromiumEnv, DBRegistryVisitDatabases) {
+  base::ScopedTempDir scoped_temp_dir;
+  ASSERT_TRUE(scoped_temp_dir.CreateUniqueTempDir());
+
+  struct NamedDB {
+    const char* tag;
+    std::string name;
+    std::unique_ptr<DB> db;
+  };
+  NamedDB named_dbs[] = {
+      {"poets"}, {"movies"}, {"recipes"}, {"misconceptions"},
+  };
+
+  // Open databases
+  for (auto& named_db : named_dbs) {
+    Options options;
+    options.create_if_missing = true;
+    std::string name =
+        scoped_temp_dir.GetPath().Append(named_db.tag).AsUTF8Unsafe();
+    DB* db;
+    Status status = leveldb_env::DBRegistry::Open(options, name, &db);
+    ASSERT_TRUE(status.ok()) << status.ToString();
+    named_db.name = name;
+    named_db.db.reset(db);
+  }
+
+  size_t visited_db_count;

[pwnall, 2017/06/22 02:50:22]

Can you initialize this to 0, so a reader doesn't have to wonder why it's not
initialized?

[DmitrySkiba, 2017/06/26 20:45:19]

Acknowledged.

+  auto db_visitor = [&](leveldb_env::DBRegistry::DBWrapper* db) {
+    for (const auto& named_db : named_dbs) {
+      if (db->name() == named_db.name) {
+        ASSERT_EQ(named_db.db.get(), db);
+        visited_db_count += 1;

[pwnall, 2017/06/22 02:50:22]

This algorithm doesn't catch the case where the visitor yields the same db
multiple times.

Here are two solutions that should not add much complexity.

1) Hav an array of flags that you memset to zero before each iteration.
2) Instead of the NamedDB struct, you start with an of C strings that have
names. You create a map<string, DB*> out of that. Each visit test creates a copy
of the map. When a DB is visited, you check that the name exists in the map and
its value matches the DB* vended by the visitor, and then you remove the name
from the map. At the end, you check that the map is empty.

How about the following alternative? 

[DmitrySkiba, 2017/06/26 20:45:19]

Good catch. Redid the test. The motivation behind DBInfo is to be able to add
(and check) more info as it's added to DBWrapper.

[pwnall, 2017/06/26 23:37:13]

Thanks for explaining! It makes sense to keep it, then.

+        return;
+      }
+    }
+    ASSERT_TRUE(false) << "Visited unknown database '" << db->name() << "'";
+  };
+
+  // Check that VisitDatabases() visits all opened databases
+  visited_db_count = 0;
+  leveldb_env::DBRegistry::GetInstance()->VisitDatabases(db_visitor);
+  ASSERT_EQ(visited_db_count, arraysize(named_dbs));
+
+  // Close couple databases

[pwnall, 2017/06/22 02:50:22]

a couple of?

[DmitrySkiba, 2017/06/26 20:45:19]

Done.

[pwnall, 2017/06/26 23:37:13]

Almost? You still need the "a".

+  named_dbs[0].db.reset();
+  named_dbs[2].db.reset();
+
+  // Check that VisitDatabases() visits only the remaining ones
+  visited_db_count = 0;
+  leveldb_env::DBRegistry::GetInstance()->VisitDatabases(db_visitor);
+  ASSERT_EQ(visited_db_count, arraysize(named_dbs) - 2);
+}
+
 int main(int argc, char** argv) { return base::TestSuite(argc, argv).Run(); }