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 and Description
static java.lang.String	STATE_DIR_NAME
static java.lang.String	STATE_FILE_EXTENSION

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
static void	deleteMetaState(java.nio.file.Path... dataLocations) Deletes all meta state directories recursively for the given data locations
XContentType	format() Returns the XContentType used to serialize xcontent on write.
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.
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.
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.
void	write(T state, java.nio.file.Path... locations) Writes the given state to the given directories.

Methods inherited from class java.lang.Object

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

Field Detail

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(XContentType format,
                              java.lang.String prefix)

Creates a new MetaDataStateFormat instance

Parameters:

format - the format of the x-content

Method Detail

format

public XContentType format()

Returns the XContentType used to serialize xcontent on write.

write

public final void write(T state,
                        java.nio.file.Path... locations)
                 throws java.io.IOException

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.

Parameters:

state - the state object to write

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

Throws:

java.io.IOException - if an IOException occurs

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

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. It tries to load the latest state determined by the states version from one or more data directories and if none of the latest states can be loaded an exception is thrown to prevent accidentally loading a previous state and silently omitting the latest state.

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