LocalBufferPool (Flink : Runtime 1.20.1 API)

java.lang.Object
- org.apache.flink.runtime.io.network.buffer.LocalBufferPool

All Implemented Interfaces:

AvailabilityProvider, BufferPool, BufferProvider, BufferRecycler
```
public class LocalBufferPool
extends Object
implements BufferPool
```
A buffer pool used to manage a number of Buffer instances from the NetworkBufferPool.
Buffer requests are mediated to the network buffer pool to ensure deadlock free operation of the network stack by limiting the number of buffers per local buffer pool. It also implements the default mechanism for buffer recycling, which ensures that every buffer is ultimately returned to the network buffer pool.
The size of this pool can be dynamically changed at runtime (setNumBuffers(int). It will then lazily return the required number of buffers to the NetworkBufferPool to match its new size.
New buffers can be requested only when numberOfRequestedMemorySegments < currentPoolSize + maxOverdraftBuffersPerGate. In other words, all buffers exceeding the currentPoolSize will be dynamically regarded as overdraft buffers.
Availability is defined as returning a non-overdraft segment on a subsequent requestBuffer()/ requestBufferBuilder() and heaving a non-blocking requestBufferBuilderBlocking(int). In particular,
- There is at least one availableMemorySegments.
- No subpartitions has reached maxBuffersPerChannel.
To ensure this contract, the implementation eagerly fetches additional memory segments from NetworkBufferPool as long as it hasn't reached maxNumberOfMemorySegments or one subpartition reached the quota.

Nested Class Summary
- Nested classes/interfaces inherited from interface org.apache.flink.runtime.io.AvailabilityProvider
  AvailabilityProvider.AvailabilityHelper
- Nested classes/interfaces inherited from interface org.apache.flink.runtime.io.network.buffer.BufferRecycler
  BufferRecycler.DummyBufferRecycler

Field Summary
- Fields inherited from interface org.apache.flink.runtime.io.AvailabilityProvider
  AVAILABLE

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`addBufferListener(BufferListener listener)` Adds a buffer availability listener to the buffer provider.
`int`	`bestEffortGetNumOfUsedBuffers()` Returns the number of used buffers of this buffer pool.
`CompletableFuture<?>`	`getAvailableFuture()`
`int`	`getEstimatedNumberOfRequestedMemorySegments()` Estimates the number of requested buffers.
`int`	`getMaxNumberOfMemorySegments()` Returns the maximum number of memory segments this buffer pool should use.
`int`	`getMaxOverdraftBuffersPerGate()` Returns the max overdraft buffer size of per gate.
`int`	`getNumberOfAvailableMemorySegments()` Returns the number memory segments, which are currently held by this buffer pool.
`int`	`getNumberOfRequestedMemorySegments()`
`int`	`getNumberOfRequiredMemorySegments()` Returns the number of guaranteed (minimum number of) memory segments of this buffer pool.
`int`	`getNumBuffers()` Returns the current size of this buffer pool.
`boolean`	`isDestroyed()` Checks whether this buffer pool has been destroyed.
`void`	`lazyDestroy()` Destroy is called after the produce or consume phase of a task finishes.
`void`	`recycle(org.apache.flink.core.memory.MemorySegment segment)` Recycles the `MemorySegment` to its original `BufferPool` instance.
`Buffer`	`requestBuffer()` Returns a `Buffer` instance from the buffer provider, if one is available.
`BufferBuilder`	`requestBufferBuilder()` Returns a `BufferBuilder` instance from the buffer provider.
`BufferBuilder`	`requestBufferBuilder(int targetChannel)` Returns a `BufferBuilder` instance from the buffer provider.
`BufferBuilder`	`requestBufferBuilderBlocking()` Returns a `BufferBuilder` instance from the buffer provider.
`BufferBuilder`	`requestBufferBuilderBlocking(int targetChannel)` Returns a `BufferBuilder` instance from the buffer provider.
`org.apache.flink.core.memory.MemorySegment`	`requestMemorySegment()` Returns a `MemorySegment` instance from the buffer provider.
`org.apache.flink.core.memory.MemorySegment`	`requestMemorySegmentBlocking()` Returns a `MemorySegment` instance from the buffer provider.
`void`	`reserveSegments(int numberOfSegmentsToReserve)` Reserves the target number of segments to this pool.
`void`	`setMaxOverdraftBuffersPerGate(int maxOverdraftBuffersPerGate)` Sets the max overdraft buffer size of per gate.
`void`	`setNumBuffers(int numBuffers)` Sets the current size of this buffer pool.
`String`	`toString()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.flink.runtime.io.AvailabilityProvider
and, isApproximatelyAvailable, isAvailable, or

- Method Detail
  - reserveSegments
```
public void reserveSegments(int numberOfSegmentsToReserve)
                     throws IOException
```
    Description copied from interface: BufferPool
    
    Reserves the target number of segments to this pool. Will throw an exception if it can not allocate enough segments.
    
    Specified by:
    
    reserveSegments in interface BufferPool
    
    Throws:
    
    IOException
  - isDestroyed
```
public boolean isDestroyed()
```
    Description copied from interface: BufferPool
    
    Checks whether this buffer pool has been destroyed.
    
    Specified by:
    
    isDestroyed in interface BufferPool
    
    Specified by:
    
    isDestroyed in interface BufferProvider
  - getNumberOfRequiredMemorySegments
```
public int getNumberOfRequiredMemorySegments()
```
    Description copied from interface: BufferPool
    
    Returns the number of guaranteed (minimum number of) memory segments of this buffer pool.
    
    Specified by:
    
    getNumberOfRequiredMemorySegments in interface BufferPool
  - getMaxNumberOfMemorySegments
```
public int getMaxNumberOfMemorySegments()
```
    Description copied from interface: BufferPool
    
    Returns the maximum number of memory segments this buffer pool should use.
    
    Specified by:
    
    getMaxNumberOfMemorySegments in interface BufferPool
    
    Returns:
    
    maximum number of memory segments to use or -1 if unlimited
  - getEstimatedNumberOfRequestedMemorySegments
```
public int getEstimatedNumberOfRequestedMemorySegments()
```
    Estimates the number of requested buffers.
    
    Returns:
    
    the same value as getMaxNumberOfMemorySegments() for bounded pools. For unbounded pools it returns an approximation based upon getNumberOfRequiredMemorySegments()
  - getNumberOfRequestedMemorySegments
```
@VisibleForTesting
public int getNumberOfRequestedMemorySegments()
```
  - getNumberOfAvailableMemorySegments
```
public int getNumberOfAvailableMemorySegments()
```
    Description copied from interface: BufferPool
    
    Returns the number memory segments, which are currently held by this buffer pool.
    
    Specified by:
    
    getNumberOfAvailableMemorySegments in interface BufferPool
  - getNumBuffers
```
public int getNumBuffers()
```
    Description copied from interface: BufferPool
    
    Returns the current size of this buffer pool.
    The size of the buffer pool can change dynamically at runtime.
    
    Specified by:
    
    getNumBuffers in interface BufferPool
  - bestEffortGetNumOfUsedBuffers
```
public int bestEffortGetNumOfUsedBuffers()
```
    Description copied from interface: BufferPool
    
    Returns the number of used buffers of this buffer pool.
    
    Specified by:
    
    bestEffortGetNumOfUsedBuffers in interface BufferPool
  - requestBuffer
```
public Buffer requestBuffer()
```
    Description copied from interface: BufferProvider
    
    Returns a Buffer instance from the buffer provider, if one is available.
    
    Specified by:
    
    requestBuffer in interface BufferProvider
    
    Returns:
    
    null if no buffer is available or the buffer provider has been destroyed.
  - requestBufferBuilder
```
public BufferBuilder requestBufferBuilder()
```
    Description copied from interface: BufferProvider
    
    Returns a BufferBuilder instance from the buffer provider. This equals to BufferProvider.requestBufferBuilder(int) with unknown target channel.
    
    Specified by:
    
    requestBufferBuilder in interface BufferProvider
    
    Returns:
    
    null if no buffer is available or the buffer provider has been destroyed.
  - requestBufferBuilder
```
public BufferBuilder requestBufferBuilder(int targetChannel)
```
    Description copied from interface: BufferProvider
    
    Returns a BufferBuilder instance from the buffer provider.
    
    Specified by:
    
    requestBufferBuilder in interface BufferProvider
    
    Parameters:
    
    targetChannel - to which the request will be accounted to.
    
    Returns:
    
    null if no buffer is available or the buffer provider has been destroyed.
  - requestBufferBuilderBlocking
```
public BufferBuilder requestBufferBuilderBlocking()
                                           throws InterruptedException
```
    Description copied from interface: BufferProvider
    
    Returns a BufferBuilder instance from the buffer provider. This equals to BufferProvider.requestBufferBuilderBlocking(int) with unknown target channel.
    If there is no buffer available, the call will block until one becomes available again or the buffer provider has been destroyed.
    
    Specified by:
    
    requestBufferBuilderBlocking in interface BufferProvider
    
    Throws:
    
    InterruptedException
  - requestMemorySegmentBlocking
```
public org.apache.flink.core.memory.MemorySegment requestMemorySegmentBlocking()
                                                                        throws InterruptedException
```
    Description copied from interface: BufferProvider
    
    Returns a MemorySegment instance from the buffer provider.
    If there is no memory segment available, the call will block until one becomes available again or the buffer provider has been destroyed.
    
    Specified by:
    
    requestMemorySegmentBlocking in interface BufferProvider
    
    Throws:
    
    InterruptedException
  - requestBufferBuilderBlocking
```
public BufferBuilder requestBufferBuilderBlocking(int targetChannel)
                                           throws InterruptedException
```
    Description copied from interface: BufferProvider
    
    Returns a BufferBuilder instance from the buffer provider.
    If there is no buffer available, the call will block until one becomes available again or the buffer provider has been destroyed.
    
    Specified by:
    
    requestBufferBuilderBlocking in interface BufferProvider
    
    Parameters:
    
    targetChannel - to which the request will be accounted to.
    
    Throws:
    
    InterruptedException
  - requestMemorySegment
```
public org.apache.flink.core.memory.MemorySegment requestMemorySegment()
```
    Description copied from interface: BufferProvider
    
    Returns a MemorySegment instance from the buffer provider.
    
    Specified by:
    
    requestMemorySegment in interface BufferProvider
    
    Returns:
    
    null if no memory segment is available or the buffer provider has been destroyed.
  - recycle
```
public void recycle(org.apache.flink.core.memory.MemorySegment segment)
```
    Description copied from interface: BufferRecycler
    
    Recycles the MemorySegment to its original BufferPool instance.
    
    Specified by:
    
    recycle in interface BufferRecycler
    
    Parameters:
    
    segment - The memory segment to be recycled.
  - lazyDestroy
```
public void lazyDestroy()
```
    Destroy is called after the produce or consume phase of a task finishes.
    
    Specified by:
    
    lazyDestroy in interface BufferPool
  - addBufferListener
```
public boolean addBufferListener(BufferListener listener)
```
    Description copied from interface: BufferProvider
    
    Adds a buffer availability listener to the buffer provider.
    The operation fails with return value false, when there is a buffer available or the buffer provider has been destroyed.
    
    Specified by:
    
    addBufferListener in interface BufferProvider
  - setNumBuffers
```
public void setNumBuffers(int numBuffers)
```
    Description copied from interface: BufferPool
    
    Sets the current size of this buffer pool.
    The size needs to be greater or equal to the guaranteed number of memory segments.
    
    Specified by:
    
    setNumBuffers in interface BufferPool
  - setMaxOverdraftBuffersPerGate
```
public void setMaxOverdraftBuffersPerGate(int maxOverdraftBuffersPerGate)
```
    Description copied from interface: BufferPool
    
    Sets the max overdraft buffer size of per gate.
    
    Specified by:
    
    setMaxOverdraftBuffersPerGate in interface BufferPool
  - getMaxOverdraftBuffersPerGate
```
public int getMaxOverdraftBuffersPerGate()
```
    Description copied from interface: BufferPool
    
    Returns the max overdraft buffer size of per gate.
    
    Specified by:
    
    getMaxOverdraftBuffersPerGate in interface BufferPool
  - getAvailableFuture
```
public CompletableFuture<?> getAvailableFuture()
```
    Specified by:
    
    getAvailableFuture in interface AvailabilityProvider
    
    Returns:
    
    a future that is completed if the respective provider is available.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class LocalBufferPool

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.flink.runtime.io.AvailabilityProvider

Nested classes/interfaces inherited from interface org.apache.flink.runtime.io.network.buffer.BufferRecycler

Field Summary

Fields inherited from interface org.apache.flink.runtime.io.AvailabilityProvider

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface org.apache.flink.runtime.io.AvailabilityProvider

Method Detail

reserveSegments

isDestroyed

getNumberOfRequiredMemorySegments

getMaxNumberOfMemorySegments

getEstimatedNumberOfRequestedMemorySegments

getNumberOfRequestedMemorySegments

getNumberOfAvailableMemorySegments

getNumBuffers

bestEffortGetNumOfUsedBuffers

requestBuffer

requestBufferBuilder

requestBufferBuilder

requestBufferBuilderBlocking

requestMemorySegmentBlocking

requestBufferBuilderBlocking

requestMemorySegment

recycle

lazyDestroy

addBufferListener

setNumBuffers

setMaxOverdraftBuffersPerGate

getMaxOverdraftBuffersPerGate

getAvailableFuture

toString