RecoveryFile is horribly broken #7
Description
So, I was curious how the recovery file stuff was actually implemented, and found some grave bugs which completely disable the feature always, and if it wasn't, would actually cause more data corruption.
For starters CorrectlyFinished is always false, because it tries to read beyond the stream end (Stream.Seek(finalRecordSize, SeekOrigin.End); instead of -finalRecordSize).
Next, it does not actually read the content of update records:, as it calls the BlockingRead() variant that expects a size and returns the buffer (and ignores the return value), so content is never filled, thus potentially "updating" a page with all zeroes.
DataTanker/DataTanker/Core/Recovery/RecoveryFile.cs
Lines 318 to 319 in ac533a6
Finally, replaying the recovery records will fail, as the recovery is attempted before Storage.IsOpen is set to true, thus when tying to e.g. update a page a chain of PageExists -> CheckStorage -> not open -> throw new InvalidOperationException occurs, and boom.
Fixing these issue should at least make the basic recovery functionality work.
I added a test to my local fork (that has Recovery renamed to Journal, among other things), that you maybe can adapt.
[TestFixture]
public class JournalTests : FileSystemStorageTestBase
{
public JournalTests()
{
StoragePath = Path.Combine(Directory.GetParent(Assembly.GetExecutingAssembly().Location).FullName,
"..\\..\\Storages");
}
[Test]
public void RecoverJournal()
{
long idx;
long deleteIndex;
using (var man = new FileSystemPageManager(4096))
using (var storage = new Storage(man)) {
storage.Open(StoragePath, PersistentStorageOpenMode.Create);
var page = man.CreatePage();
idx = page.Index;
deleteIndex = man.CreatePage().Index;
}
using (var man = new FileSystemPageManager(4096))
using (var storage = new Storage(man)) {
storage.Open(StoragePath, PersistentStorageOpenMode.OpenExisting);
var page = man.FetchPage(idx);
Assert.AreEqual(page.Index, idx);
Assert.AreNotEqual(page.Content[10], 0xff);
Assert.True(man.PageExists(deleteIndex));
}
string file;
using (var man = new FileSystemPageManager(4096))
using (var storage = new Storage(man))
using (var journal = new JournalFile(man, man.PageSize)) {
storage.Open(StoragePath, PersistentStorageOpenMode.OpenExisting);
var page = man.FetchPage(idx);
idx = page.Index;
man.Dispose();
Assert.AreEqual(page.Index, idx);
Assert.AreNotEqual(page.Content[10], 0xff);
journal.WriteDeletePageRecord(deleteIndex);
// Update twice with different pages to make sure the latest one wins
page.Content[9] = 0xaa;
page.Content[10] = 0xaa;
journal.WriteUpdatePageRecord(page);
page.Content[10] = 0xff;
journal.WriteUpdatePageRecord(page);
journal.WriteFinalMarker();
file = journal.JournalFileName;
}
Assert.True(File.Exists(file));
Assert.GreaterOrEqual(new FileInfo(file).Length, 1);
Assert.AreNotEqual(idx, 0);
using (var man = new FileSystemPageManager(4096))
using (var storage = new Storage(man)) {
storage.Open(StoragePath, PersistentStorageOpenMode.OpenExisting);
var page = man.FetchPage(idx);
Assert.AreEqual(page.Index, idx);
Assert.AreEqual(page.Content[9], 0xaa);
Assert.AreEqual(page.Content[10], 0xff);
Assert.False(man.PageExists(deleteIndex));
Assert.AreEqual(man.CreatePage().Index, deleteIndex);
}
}
}