Class WriteBufferManager

Namespace

RocksDbNet

Assembly

RocksDb.Net.dll

A memory budget for memtables, shared across column families and across databases. Maps to rocksdb_write_buffer_manager_t.

public sealed class WriteBufferManager : RocksDbHandle, IDisposable

Inheritance

object

RocksDbHandle

WriteBufferManager

Implements

IDisposable

Inherited Members

RocksDbHandle.Handle

RocksDbHandle.Owned

RocksDbHandle.IsDisposed

RocksDbHandle.ThrowIfDisposed()

RocksDbHandle.Dispose()

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

WriteBufferSize bounds one memtable. It says nothing about the total, so a process with many column families or several databases has no way to cap how much memory their memtables take together. This does.

Attach it with WriteBufferManager. RocksDb takes a shared reference, so this object may be disposed once assigned, and sharing one instance between databases is the point: they then draw on a common budget rather than each having their own.

Properties

AllowStall

Whether writers are stalled when the budget is exhausted.

public bool AllowStall { set; }

Property Value

bool

Remarks

Write-only: RocksDb exposes no getter for it.

BufferSize

The budget, in bytes. Zero disables enforcement.

public ulong BufferSize { get; set; }

Property Value

ulong

CostsToCache

Whether this manager charges its memory against a cache.

public bool CostsToCache { get; }

Property Value

bool

DummyEntriesInCacheUsage

Memory the manager has reserved in its cache through placeholder entries, in bytes.

public ulong DummyEntriesInCacheUsage { get; }

Property Value

ulong

Remarks

Zero unless the manager was created with a cache. This is how memtable memory is made visible to the cache's accounting.

IsEnabled

Whether the manager is enforcing a budget, which it is only when the buffer size is non-zero.

public bool IsEnabled { get; }

Property Value

bool

MemoryUsage

Memory currently attributed to memtables, in bytes, including those already sealed and waiting to be flushed.

public ulong MemoryUsage { get; }

Property Value

ulong

MutableMemtableMemoryUsage

Memory attributed to memtables still accepting writes, in bytes.

public ulong MutableMemtableMemoryUsage { get; }

Property Value

ulong

Remarks

The difference between this and MemoryUsage is memory held by memtables that are sealed and waiting on a flush. A large gap means flushing is not keeping up.

Methods

Create(ulong, Cache, bool)

Creates a manager that charges its memory against cache, so that memtables and cached blocks compete for one budget.

public static WriteBufferManager Create(ulong bufferSize, Cache cache, bool allowStall = false)

Parameters

bufferSize ulong

cache Cache

allowStall bool

Returns

WriteBufferManager

Remarks

Useful when the real constraint is total process memory rather than memtable memory specifically. The manager inserts placeholder entries into the cache to account for what the memtables hold; see DummyEntriesInCacheUsage.

Create(ulong, bool)

Creates a manager with a budget of bufferSize bytes.

public static WriteBufferManager Create(ulong bufferSize, bool allowStall = false)

Parameters

bufferSize ulong

The total memtable budget. Zero disables the manager, which then tracks usage without enforcing anything.

allowStall bool

Whether writers are stalled when the budget is exhausted. When false, the budget is enforced by flushing sooner rather than by blocking.

Returns

WriteBufferManager

DisposeHandle()

Releases the native handle. Called during disposal.

protected override void DisposeHandle()

Remarks

Protected rather than public: it destroys the native object without marking this instance disposed or clearing the handle, so calling it from outside and then disposing normally would free the same pointer twice. It was the most Dispose-looking member on the type. Callers want Dispose().