Module me.ahoo.cosid.core

Package me.ahoo.cosid.lease

Class StaticSlot

java.lang.Object

me.ahoo.cosid.lease.StaticSlot

All Implemented Interfaces:

AutoCloseable, SlotHandle

public final class StaticSlot
extends Object
implements SlotHandle, AutoCloseable

A slot the user keeps unique (manual or StatefulSet ordinal), with a time window from a local file (05-machine-lease.md §4.4): the file holds the ceiling, written ahead and fsynced before use, so a crash followed by a clock regression cannot repeat ids. Without a file there is no regression protection.

With a file, one long-lived task on the executor writes the ceiling ahead again whenever less than ahead/2 of the window is left; the executor must run tasks asynchronously.

Its public constructors are the assembly entry CosIdRuntime uses (R2-core-03): they keep their signatures, and a new parameter comes only through a builder or a static factory, never as one more positional overload (api-freeze.md §4.2).

Constructor Summary

Constructors

Constructor	Description
StaticSlot(int slot, int bits, Optional<Path> stateFile, Duration ahead, Optional<Instant> notBefore, Executor executor, TimeSource time)	A static slot; start() reads the window.

Method Summary

Modifier and Type	Method	Description
int	bits()
void	close()	Stops extending the window; the ceiling written ahead stays in the file.
void	close(long lastIssued)	Writes the exact last issued timestamp as the ceiling, so the next start begins right after it.
SlotBinding	current()	The current binding: one volatile read.
int	slot()
void	start()	Reads the floor from the file and writes the first ceiling ahead.

Methods inherited from class java.lang.Object

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

Constructor Details

StaticSlot

public StaticSlot(int slot,
 int bits,
 Optional<Path> stateFile,
 Duration ahead,
 Optional<Instant> notBefore,
 Executor executor,
 TimeSource time)

A static slot; start() reads the window.

Parameters:

slot - the slot, in [0, 2^bits)

bits - the slot bits

stateFile - the window file; none means no clock regression protection

ahead - how far ahead the ceiling is written; default 10s

notBefore - the floor when the file does not exist yet (given by the migration tool)

executor - runs the asynchronous rewrites of the ceiling

time - the time source

Method Details

slot

public int slot()

bits

public int bits()

start

public void start()

Reads the floor from the file and writes the first ceiling ahead.

current

public SlotBinding current()

Description copied from interface: SlotHandle

The current binding: one volatile read. A generator reads it once per id.

Specified by:

current in interface SlotHandle

Returns:

the binding

close

public void close(long lastIssued)

Writes the exact last issued timestamp as the ceiling, so the next start begins right after it.

Parameters:

lastIssued - the largest timestamp issued on the slot, in milliseconds

close

public void close()

Stops extending the window; the ceiling written ahead stays in the file.

Specified by:

close in interface AutoCloseable