ZoneTree 1.2.0

ZoneTree

ZoneTree is a persistent, high-performance, transactional, and ACID-compliant key-value database for .NET. It can operate in memory or on disk. (Optimized for SSDs)

ZoneTree is a lightweight, transactional and high-performance LSM Tree for .NET.

It is four times faster than Facebook's RocksDB.

Why ZoneTree?

1. It is pure C#.
2. It is fast. See benchmark below.
3. Your data is protected against crashes / power cuts.
4. Supports transactional and non-transactional access with blazing speeds and ACID guarantees.
5. You can embed your database into your assembly. Therefore, you don't have to pay the cost of maintaining/shipping another database product along with yours.

How fast is it?

Benchmark Configuration:

DiskCompressionBlockSize = 1024 * 1024 * 1;
WALCompressionBlockSize = 1024 * 1024;
DiskSegmentMode = DiskSegmentMode.MultipleDiskSegments;

Additional Notes: According to our tests, ZoneTree is stable and fast even with big data. Tested up to 200M records in desktop computers till now.

ZoneTree offers 3 WAL modes to let you make a flexible tradeoff.

• The Immediate mode provides maximum durability but slower write speed. In case of a crash/power cut, the immediate mode ensures that the inserted data is not lost. RocksDb does not have immediate WAL mode. It has a WAL mode similar to the CompressedImmediate mode. (reference:http://rocksdb.org/blog/2017/08/25/flushwal.html)

• The CompressedImmediate mode provides faster write speed but less durability. Compression requires chunks to be filled before appending them into the WAL file. It is possible to enable a periodic job to persist decompressed tail records into a separate location in a specified interval. See IWriteAheadLogProvider options for more details.

• The Lazy mode provides faster write speed but less durability. Log entries are queued to be written in a separate thread. Lazy mode uses compression in WAL files and provides immediate tail record persistence.

Environment:

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.22000
Intel Core i7-6850K CPU 3.60GHz (Skylake), 1 CPU, 12 logical and 6 physical cores
64 GB DDR4 Memory
SSD: Samsung SSD 850 EVO 1TB
Config: 1M mutable segment size, 2M readonly segments merge-threshold

How to use ZoneTree?

The following sample demonstrates creating a database.

  var dataPath = "data/mydatabase";
  using var zoneTree = new ZoneTreeFactory<int, string>()
    .SetComparer(new Int32ComparerAscending())
    .SetDataDirectory(dataPath)
    .SetKeySerializer(new Int32Serializer())
    .SetValueSerializer(new Utf8StringSerializer())
    .OpenOrCreate();
    
    // atomic (thread-safe) on single mutable-segment.
    zoneTree.Upsert(39, "Hello Zone Tree!");
    
    // atomic across all segments
    zoneTree.TryAtomicAddOrUpdate(39, "a", (x) => x + "b");

How to maintain LSM Tree?

Big LSM Trees require maintenance tasks. ZoneTree provides the IZoneTreeMaintenance interface to give you full power on maintenance tasks. It also comes with a default maintainer to let you focus on your business logic without wasting time with LSM details. You can start using the default maintainer like in the following sample code. Note: For small data you don't need a maintainer.

  var dataPath = "data/mydatabase";

  // 1. Create your ZoneTree
  using var zoneTree = new ZoneTreeFactory<int, string>()
    .SetComparer(new Int32ComparerAscending())
    .SetDataDirectory(dataPath)
    .SetKeySerializer(new Int32Serializer())
    .SetValueSerializer(new Utf8StringSerializer())
    .OpenOrCreate();
 
  using var maintainer = new BasicZoneTreeMaintainer<int, string>(zoneTree);

  // 2. Read/Write data
  zoneTree.Upsert(39, "Hello ZoneTree!");

  // 3. Complete maintainer running tasks.
  maintainer.CompleteRunningTasks();

How to delete keys?

In LSM trees, the deletions are handled by upserting key/value with deleted flag. Later on, during the compaction stage, the actual deletion happens. ZoneTree does not implement this flag format by default. It lets the user to define the suitable deletion flag themselves. For example, the deletion flag might be defined by user as -1 for int values. If user wants to use any int value as a valid record, then the value-type should be changed. For example, one can define the following struct and use this type as a value-type.

[StructLayout(LayoutKind.Sequential)]
struct MyDeletableValueType {
   int Number; 
   bool IsDeleted; 
}

You can micro-manage the tree size with ZoneTree. The following sample shows how to configure the deletion markers for your database.

using var zoneTree = new ZoneTreeFactory<int, int>()
  // Additional stuff goes here
  .SetIsValueDeletedDelegate((in int x) => x == -1)
  .SetMarkValueDeletedDelegate((ref int x) => x = -1)
  .OpenOrCreate();  

or

using var zoneTree = new ZoneTreeFactory<int, MyDeletableValueType>()
  // Additional stuff goes here
  .SetIsValueDeletedDelegate((in MyDeletableValueType x) => x.IsDeleted)
  .SetMarkValueDeletedDelegate((ref MyDeletableValueType x) => x.IsDeleted = true)
  .OpenOrCreate();  

If you forget to provide the deletion marker delegates, you can never delete the record from your database.

How to iterate over data?

Iteration is possible in both directions, forward and backward. Unlike other LSM tree implementations, iteration performance is equal in both directions. The following sample shows how to do the iteration.

 using var zoneTree = new ZoneTreeFactory<int, int>()
    // Additional stuff goes here
    .OpenOrCreate();
 using var iterator = zoneTree.CreateIterator();
 while(iterator.Next()) {
    var key = iterator.CurrentKey;
    var value = iterator.CurrentValue;
 } 
 
 using var reverseIterator = zoneTree.CreateReverseIterator();
 while(reverseIterator.Next()) {
    var key = reverseIterator.CurrentKey;
    var value = reverseIterator.CurrentValue;
 }

How to iterate starting with a key (Seekable Iterator)?

ZoneTreeIterator provides Seek() method to jump into any record with in O(log(n)) complexity. That is useful for doing prefix search with forward-iterator or with backward-iterator.

 using var zoneTree = new ZoneTreeFactory<string, int>()
    // Additional stuff goes here
    .OpenOrCreate();
 using var iterator = zoneTree.CreateIterator();
 // iterator jumps into the first record starting with "SomePrefix" in O(log(n)) complexity. 
 iterator.Seek("SomePrefix");
 
 //iterator.Next() complexity is O(1)
 while(iterator.Next()) {
    var key = iterator.CurrentKey;
    var value = iterator.CurrentValue;
 } 

Transaction Support

ZoneTree supports Optimistic Transactions. It is proud to announce that the ZoneTree is ACID-compliant. Of course, you can use non-transactional API for the scenarios where eventual consistency is sufficient.

ZoneTree supports 3 way of doing transactions.

1. Fluent Transactions with ready to use retry capability.
2. Classical Transaction API.
3. Exceptionless Transaction API.

The following sample shows how to do the transactions with ZoneTree Fluent Transaction API.

using var zoneTree = new ZoneTreeFactory<int, int>()
    // Additional stuff goes here
    .OpenOrCreateTransactional();
using var transaction =
    zoneTree
        .BeginFluentTransaction()
        .Do((tx) => zoneTree.UpsertNoThrow(tx, 3, 9))
        .Do((tx) =>
        {
            if (zoneTree.TryGetNoThrow(tx, 3, out var value).IsAborted)
                return TransactionResult.Aborted();
            if (zoneTree.UpsertNoThrow(tx, 3, 21).IsAborted)
                return TransactionResult.Aborted();
            return TransactionResult.Success();
        })
        .SetRetryCountForPendingTransactions(100)
        .SetRetryCountForAbortedTransactions(10);
    await transaction.CommitAsync();

The following sample shows traditional way of doing transactions with ZoneTree.

 using var zoneTree = new ZoneTreeFactory<int, int>()
    // Additional stuff goes here
    .OpenOrCreateTransactional();
 try 
 {
     var txId = zoneTree.BeginTransaction();
     zoneTree.TryGet(txId, 3, out var value);
     zoneTree.Upsert(txId, 3, 9);
     var result = zoneTree.Prepare(txId);
     while (result.IsPendingTransactions) {
         Thread.Sleep(100);
         result = zoneTree.Prepare(txId);
     }
     zoneTree.Commit(txId);
  }
  catch(TransactionAbortedException e)
  {
      //retry or cancel
  }

Features

I need more information. Where can I find it?

I am going to write more detailed documentation as soon as possible.

I want to contribute. What can I do?

I appreciate any contribution to the project. These are the things I do think we need at the moment:

1. Write tests / benchmarks.
2. Write documentation.
3. Convert documentation to a website using static site generators.
4. Feature requests & bug fixes.
5. Performance improvements.