Package me.ahoo.cosid.segment

Class SegmentChainId

java.lang.Object

me.ahoo.cosid.segment.SegmentChainId

All Implemented Interfaces:

IdGenerator, SegmentId, Statistical, StringIdGenerator

public class SegmentChainId
extends Object
implements SegmentId

Segment chain algorithm ID generator.

This implementation extends the basic segment algorithm by organizing segments into a chain structure, providing improved performance and resilience through prefetching and dynamic scaling.

Key features of the segment chain algorithm:

• Chain Structure: Segments are organized in a linked chain
• Prefetching: Segments are prefetched in the background
• Dynamic Scaling: Prefetch distance adapts to demand
• High Availability: Multiple segments provide resilience

The algorithm works by:

1. Maintaining a chain of ID segments
2. Generating IDs from the head of the chain
3. Prefetching new segments in the background
4. Dynamically adjusting prefetch distance based on demand

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
class	SegmentChainId.PrefetchJob	Background prefetch job for segment chain ID generation.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_SAFE_DISTANCE	The default safe distance for prefetching segments.

Fields inherited from interface me.ahoo.cosid.segment.SegmentId

ONE_STEP

Constructor Summary

Constructors

Constructor	Description
SegmentChainId(long idSegmentTtl, int safeDistance, IdSegmentDistributor maxIdDistributor, PrefetchWorkerExecutorService prefetchWorkerExecutorService)	Create a new SegmentChainId with custom configuration.
SegmentChainId(IdSegmentDistributor maxIdDistributor)	Create a new SegmentChainId with default configuration.

Method Summary

Modifier and Type	Method	Description
IdSegment	current()	Get the current ID segment (the head of the chain).
long	generate()	Generate a new distributed ID.
IdSegmentChain	getHead()	Get the head of the segment chain.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface me.ahoo.cosid.IdGenerator

generateAsString, idConverter

Methods inherited from interface me.ahoo.cosid.segment.SegmentId

stat

Field Details

DEFAULT_SAFE_DISTANCE

public static final int DEFAULT_SAFE_DISTANCE

The default safe distance for prefetching segments.

This is the minimum number of segments to keep prefetched ahead of the current consumption point to ensure continuous ID generation.

See Also:

• Constant Field Values

Constructor Details

SegmentChainId

public SegmentChainId(IdSegmentDistributor maxIdDistributor)

Create a new SegmentChainId with default configuration.

This constructor creates a generator with infinite segment TTL, default safe distance, and the default prefetch worker executor.

Parameters:

maxIdDistributor - The distributor for allocating new segments

SegmentChainId

public SegmentChainId(long idSegmentTtl,
 int safeDistance,
 IdSegmentDistributor maxIdDistributor,
 PrefetchWorkerExecutorService prefetchWorkerExecutorService)

Create a new SegmentChainId with custom configuration.

This constructor allows full control over all parameters of the segment chain ID generator.

Parameters:

idSegmentTtl - The time-to-live for segments

safeDistance - The safe distance for prefetching

maxIdDistributor - The distributor for allocating new segments

prefetchWorkerExecutorService - The executor for prefetch jobs

Method Details

current

public IdSegment current()

Get the current ID segment (the head of the chain).

This method returns the segment from which IDs are currently being allocated. In the chain implementation, this is the head of the segment chain.

Specified by:

current in interface SegmentId

Returns:

The current ID segment (head of the chain)

getHead

public IdSegmentChain getHead()

Get the head of the segment chain.

This method provides direct access to the head of the segment chain, which contains additional chain-specific information beyond the basic segment interface.

Returns:

The head of the segment chain

generate

public long generate()

Generate a new distributed ID.

This method generates a unique ID by traversing the segment chain and allocating an ID from the first available segment. If no segments are available, it triggers prefetching of new segments.

Specified by:

generate in interface IdGenerator

Returns:

A unique distributed ID