org.neo4j.io.pagecache

Interface PageSwapperFactory

public interface PageSwapperFactory

Creates PageSwappers for the given files.

A PageSwapper is responsible for swapping file pages in and out of memory.

The PageSwapperFactory presumably knows about what file system to use.

To be able to create PageSwapper factory need to be configured first using appropriate configure call. Note that this API is only intended to be used by a PageCache implementation. It should never be used directly by user code.

Method Summary

Modifier and Type	Method and Description
void	close() Close and release any resources associated with this PageSwapperFactory, that it may have opened or acquired during its construction or use.
PageSwapper	createPageSwapper(File file, int filePageSize, PageEvictionCallback onEviction, boolean createIfNotExist) Create a PageSwapper for the given file.
int	getCachePageSizeHint() Get the most optimal cache page size (in bytes) for these PageSwapper implementations.
FileSystemAbstraction	getFileSystemAbstraction() Get the FileSystemAbstraction that represents the underlying storage for the page swapper.
long	getRequiredBufferAlignment() Get the unit of alignment that the swappers require of the memory buffers.
String	implementationName() Get the name of this PageSwapperFactory implementation, for configuration purpose.
boolean	isCachePageSizeHintStrict() Gives true if the getCachePageSizeHint() is the only cache page size that is supported for these PageSwapper implementations, otherwise false.
void	open(FileSystemAbstraction fs, org.neo4j.graphdb.config.Configuration config) Open page swapper factory with provided filesystem and config
void	syncDevice() Forces all prior writes made through all non-closed PageSwappers that this factory has created, to all the relevant devices, such that the writes are durable when this call returns.

Method Detail

open

void open(FileSystemAbstraction fs,
          org.neo4j.graphdb.config.Configuration config)

Open page swapper factory with provided filesystem and config

Parameters:

fs - file system to use in page swappers

config - custom page swapper configuration

getFileSystemAbstraction

FileSystemAbstraction getFileSystemAbstraction()

Get the FileSystemAbstraction that represents the underlying storage for the page swapper.

implementationName

String implementationName()

Get the name of this PageSwapperFactory implementation, for configuration purpose.

getCachePageSizeHint

int getCachePageSizeHint()

Get the most optimal cache page size (in bytes) for these PageSwapper implementations.

isCachePageSizeHintStrict

boolean isCachePageSizeHintStrict()

Gives true if the getCachePageSizeHint() is the only cache page size that is supported for these PageSwapper implementations, otherwise false.

getRequiredBufferAlignment

long getRequiredBufferAlignment()

Get the unit of alignment that the swappers require of the memory buffers. For instance, if page alignment is required for doing direct IO, then UnsafeUtil.pageSize() can be returned.

Returns:

The required buffer alignment byte multiple.

createPageSwapper

PageSwapper createPageSwapper(File file,
                              int filePageSize,
                              PageEvictionCallback onEviction,
                              boolean createIfNotExist)
                       throws IOException

Create a PageSwapper for the given file.

Parameters:

file - The file that the PageSwapper will move file pages in and out of.

filePageSize - The size of the pages in the file. Presumably a multiple of some record size.

onEviction - The PageSwapper will be told about evictions, and has the responsibility of informing the PagedFile via this callback.

createIfNotExist - When true, creates the given file if it does not exist, instead of throwing an exception.

Returns:

A working PageSwapper instance for the given file.

Throws:

IOException - If the PageSwapper could not be created, for instance if the underlying file could not be opened, or the given file does not exist and createIfNotExist is false.

syncDevice

void syncDevice()
         throws IOException

Forces all prior writes made through all non-closed PageSwappers that this factory has created, to all the relevant devices, such that the writes are durable when this call returns.

This method has no effect if the PageSwapper.force() method forces the writes for the individual file. The PageCache.flushAndForce() method will first call force on the PageSwappers for all mapped files, then call syncDevice on the PageSwapperFactory. This way, the writes are always made durable regardless of which method that does the forcing.

Throws:

IOException

close

void close()

Close and release any resources associated with this PageSwapperFactory, that it may have opened or acquired during its construction or use.

This method cannot be called before all of the opened PageSwappers have been closed, and it is guaranteed that no new page swappers will be created after this method has been called.