Package org.elasticsearch.gateway

Class MetaDataStateFormat<T>

java.lang.Object

org.elasticsearch.gateway.MetaDataStateFormat<T>

Type Parameters:

T - the type of the XContent base data-structure

public abstract class MetaDataStateFormat<T>
extends java.lang.Object

MetaDataStateFormat is a base class to write checksummed XContent based files to one or more directories in a standardized directory structure.

Field Summary

Fields

Modifier and Type	Field	Description
static XContentType	FORMAT
static java.lang.String	STATE_DIR_NAME
static java.lang.String	STATE_FILE_EXTENSION

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	MetaDataStateFormat(java.lang.String prefix)	Creates a new MetaDataStateFormat instance

Method Summary

Modifier and Type	Method	Description
void	cleanupOldFiles(long currentGeneration, java.nio.file.Path[] locations)	Clean ups all state files not matching passed generation.
static void	deleteMetaState(java.nio.file.Path... dataLocations)	Deletes all meta state directories recursively for the given data locations
abstract T	fromXContent(XContentParser parser)	Reads a new instance of the state from the given XContentParser Subclasses need to implement this class for theirs specific state.
java.lang.String	getPrefix()
java.lang.String	getStateFileName(long generation)
T	loadGeneration(org.apache.logging.log4j.Logger logger, NamedXContentRegistry namedXContentRegistry, long generation, java.nio.file.Path... dataLocations)	Tries to load the state of particular generation from the given data-locations.
T	loadLatestState(org.apache.logging.log4j.Logger logger, NamedXContentRegistry namedXContentRegistry, java.nio.file.Path... dataLocations)	Tries to load the latest state from the given data-locations.
Tuple<T,java.lang.Long>	loadLatestStateWithGeneration(org.apache.logging.log4j.Logger logger, NamedXContentRegistry namedXContentRegistry, java.nio.file.Path... dataLocations)	Tries to load the latest state from the given data-locations.
protected org.apache.lucene.store.Directory	newDirectory(java.nio.file.Path dir)
protected XContentBuilder	newXContentBuilder(XContentType type, java.io.OutputStream stream)
T	read(NamedXContentRegistry namedXContentRegistry, java.nio.file.Path file)	Reads the state from a given file and compares the expected version against the actual version of the state.
abstract void	toXContent(XContentBuilder builder, T state)	Writes the given state to the given XContentBuilder Subclasses need to implement this class for theirs specific state.
long	write(T state, java.nio.file.Path... locations)	Writes the given state to the given directories.
long	writeAndCleanup(T state, java.nio.file.Path... locations)	Writes the given state to the given directories and performs cleanup of old state files if the write succeeds or newly created state file if write fails.

Methods inherited from class java.lang.Object

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

Field Detail

FORMAT

public static final XContentType FORMAT

STATE_DIR_NAME

public static final java.lang.String STATE_DIR_NAME

See Also:

Constant Field Values

STATE_FILE_EXTENSION

public static final java.lang.String STATE_FILE_EXTENSION

See Also:

Constant Field Values

Constructor Detail

MetaDataStateFormat

protected MetaDataStateFormat(java.lang.String prefix)

Creates a new MetaDataStateFormat instance

Method Detail

writeAndCleanup

public final long writeAndCleanup(T state,
                                  java.nio.file.Path... locations)
                           throws WriteStateException

Writes the given state to the given directories and performs cleanup of old state files if the write succeeds or newly created state file if write fails. See also write(Object, Path...) and cleanupOldFiles(long, Path[]).

Throws:

WriteStateException

write

public final long write(T state,
                        java.nio.file.Path... locations)
                 throws WriteStateException

Writes the given state to the given directories. The state is written to a state directory ("_state") underneath each of the given file locations and is created if it doesn't exist. The state is serialized to a temporary file in that directory and is then atomically moved to it's target filename of the pattern {prefix}{version}.st. If this method returns without exception there is a guarantee that state is persisted to the disk and loadLatestState will return it.
This method always performs cleanup of temporary files regardless whether it succeeds or fails. Cleanup logic for state files is more involved. If this method fails with an exception, it performs cleanup of newly created state file. But if this method succeeds, it does not perform cleanup of old state files. If this write succeeds, but some further write fails, you may want to rollback the transaction and keep old file around. After transaction is finished use cleanupOldFiles(long, Path[]) for the clean-up. If this write is not a part of bigger transaction, consider using writeAndCleanup(Object, Path...) method instead.

Parameters:

state - the state object to write

locations - the locations where the state should be written to.

Returns:

generation of newly written state.

Throws:

WriteStateException - if some exception during writing state occurs. See also WriteStateException.isDirty().

newXContentBuilder

protected XContentBuilder newXContentBuilder(XContentType type,
                                             java.io.OutputStream stream)
                                      throws java.io.IOException

Throws:

java.io.IOException

toXContent

public abstract void toXContent(XContentBuilder builder,
                                T state)
                         throws java.io.IOException

Writes the given state to the given XContentBuilder Subclasses need to implement this class for theirs specific state.

Throws:

java.io.IOException

fromXContent

public abstract T fromXContent(XContentParser parser)
                        throws java.io.IOException

Reads a new instance of the state from the given XContentParser Subclasses need to implement this class for theirs specific state.

Throws:

java.io.IOException

read

public final T read(NamedXContentRegistry namedXContentRegistry,
                    java.nio.file.Path file)
             throws java.io.IOException

Reads the state from a given file and compares the expected version against the actual version of the state.

Throws:

java.io.IOException

newDirectory

protected org.apache.lucene.store.Directory newDirectory(java.nio.file.Path dir)
                                                  throws java.io.IOException

Throws:

java.io.IOException

cleanupOldFiles

public void cleanupOldFiles(long currentGeneration,
                            java.nio.file.Path[] locations)

Clean ups all state files not matching passed generation.

Parameters:

currentGeneration - state generation to keep.

locations - state paths.

getStateFileName

public java.lang.String getStateFileName(long generation)

loadGeneration

public T loadGeneration(org.apache.logging.log4j.Logger logger,
                        NamedXContentRegistry namedXContentRegistry,
                        long generation,
                        java.nio.file.Path... dataLocations)

Tries to load the state of particular generation from the given data-locations. If any of data locations contain state files with given generation, state will be loaded from these state files.

Parameters:

logger - a logger instance.

generation - the generation to be loaded.

dataLocations - the data-locations to try.

Returns:

the state of asked generation or null if no state was found.

loadLatestStateWithGeneration

public Tuple<T,java.lang.Long> loadLatestStateWithGeneration(org.apache.logging.log4j.Logger logger,
                                                                   NamedXContentRegistry namedXContentRegistry,
                                                                   java.nio.file.Path... dataLocations)
                                                            throws java.io.IOException

Tries to load the latest state from the given data-locations.

Parameters:

logger - a logger instance.

dataLocations - the data-locations to try.

Returns:

tuple of the latest state and generation. (-1, null) if no state is found.

Throws:

java.io.IOException

loadLatestState

public T loadLatestState(org.apache.logging.log4j.Logger logger,
                         NamedXContentRegistry namedXContentRegistry,
                         java.nio.file.Path... dataLocations)
                  throws java.io.IOException

Tries to load the latest state from the given data-locations.

Parameters:

logger - a logger instance.

dataLocations - the data-locations to try.

Returns:

the latest state or null if no state was found.

Throws:

java.io.IOException

deleteMetaState

public static void deleteMetaState(java.nio.file.Path... dataLocations)
                            throws java.io.IOException

Deletes all meta state directories recursively for the given data locations

Parameters:

dataLocations - the data location to delete

Throws:

java.io.IOException

getPrefix

public java.lang.String getPrefix()