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Object Pooling

Nidus provides a thread-safe generic object pool (TObjectPool<T>) and a TComponent variant. Pooling eliminates repeated allocation of expensive objects under high concurrency.

Registering a pool​

Generic objects​

GetNidus
  .UsePools<TMyHeavyResource>(128)   // max pool size = 128
  .Start(TAppModule.Create);

This calls TPoolRegistry.RegisterDefaultObjectPool<TMyHeavyResource>(128) internally.

TComponent subclasses​

GetNidus
  .UsePools<TMyDbConnection>(32, AOwner,
    procedure(C: TMyDbConnection)
    begin
      C.Reset;   // called before returning to pool
    end)
  .Start(TAppModule.Create);

Or the equivalent alias:

GetNidus.UseComponentPool<TMyDbConnection>(32, AOwner, ResetProc);

Custom registry​

Provide your own IPoolRegistry implementation:

GetNidus.UsePools(TMyPoolRegistry.Create);

Acquiring and releasing objects​

Via WithPool​

The safest pattern — automatically acquires and releases around the callback:

GetNidus.WithPool<TMyHeavyResource>(
  procedure(R: TMyHeavyResource)
  begin
    R.DoWork;
  end);

With a named key (when multiple pools exist for the same type):

GetNidus.WithPool<TMyHeavyResource>('v2',
  procedure(R: TMyHeavyResource)
  begin
    R.DoWork;
  end);

Source: TNidus.WithPool<T> delegates to TPoolHelpers.WithPool<T> (Nidus.Pooling.Helpers).

Via IPoolRegistry directly​

var LPool := GetNidus.Pools;
var LObj  := LPool.Acquire<TMyHeavyResource>;
try
  LObj.DoWork;
finally
  LPool.Release(LObj);
end;

Pool internals​

TObjectPool<T> wraps a TQueue<T> protected by a TCriticalSection. Behaviour:

  • Acquire: dequeues an existing instance if available; otherwise calls T.Create.
  • Release: enqueues the instance if Count < MaxSize; otherwise frees it.
  • MaxSize defaults to 256 for object pools, 32 for component pools.

Source: Nidus.ObjectPool — TObjectPool<T>, TObjectPoolAdapter<T>.

Accessing the pool registry​

var LRegistry := GetNidus.Pools;   // returns IPoolRegistry

SetGlobalPoolRegistry / GetGlobalPoolRegistry manage the global singleton. Source: Nidus.Pooling.Interfaces.