net.openhft.chronicle.map.ChronicleMap Maven / Gradle / Ivy
/*
* Copyright 2012-2018 Chronicle Map Contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package net.openhft.chronicle.map;
import net.openhft.chronicle.bytes.Byteable;
import net.openhft.chronicle.core.util.SerializableFunction;
import net.openhft.chronicle.hash.ChronicleHash;
import net.openhft.chronicle.hash.serialization.SizedReader;
import net.openhft.chronicle.hash.serialization.SizedWriter;
import org.jetbrains.annotations.NotNull;
import java.io.Closeable;
import java.io.File;
import java.io.IOException;
import java.io.Serializable;
import java.lang.reflect.Type;
import java.util.Map;
import java.util.concurrent.ConcurrentMap;
/**
* {@code ChronicleMap} provides concurrent access to a Chronicle Map key-value store from a
* JVM process.
*
*
For information on
- how to construct a {@code ChronicleMap}
- {@code
* ChronicleMap} flavors and properties
- available configurations
see {@link
* ChronicleMapBuilder} documentation.
*
*
Functionally this interface defines some methods supporting garbage-free off-heap programming:
* {@link #getUsing(Object, Object)}, {@link #acquireUsing(Object, Object)}.
*
*
Roughly speaking, {@code ChronicleMap} compares keys and values by their binary serialized
* form, that shouldn't necessary be the same equality relation as defined by built-in {@link
* Object#equals(Object)} method, which is prescribed by general {@link Map} contract.
*
*
Note that {@code ChronicleMap} extends {@link Closeable}, don't forget to {@linkplain #close()
* close} map when it is no longer needed.
*
* @param the map key type
* @param the map value type
* @see ChronicleMapBuilder#create()
* @see ChronicleMapBuilder#createPersistedTo(File)
* @see ChronicleMapBuilder#createOrRecoverPersistedTo(File, boolean)
*/
public interface ChronicleMap extends ConcurrentMap,
ChronicleHash, MapSegmentContext,
ExternalMapQueryContext> {
/**
* Delegates to {@link ChronicleMapBuilder#of(Class, Class)} for convenience.
*
* @param keyClass class of the key type of the Chronicle Map to create
* @param valueClass class of the value type of the Chronicle Map to create
* @param the key type of the Chronicle Map to create
* @param the value type of the Chronicle Map to create
* @return a new {@code ChronicleMapBuilder} for the given key and value classes
*/
static ChronicleMapBuilder of(Class keyClass, Class valueClass) {
return ChronicleMapBuilder.of(keyClass, valueClass);
}
/**
* Returns the value to which the specified key is mapped, or {@code null} if this map contains
* no mapping for the key.
*
*
If the value class allows reusing, consider {@link #getUsing(Object, Object)} method
* instead of this to reduce garbage creation. Read the section about usage
* patterns in the Chronicle Map 3 Tutorial for more.
*
* @param key the key whose associated value is to be returned
* @return the value to which the specified key is mapped after this method call, or {@code
* null} if no value is mapped
* @see #getUsing(Object, Object)
*/
@Override
V get(Object key);
/**
* Returns the value to which the specified key is mapped, read to the provided {@code value}
* object, if possible, or returns {@code null}, if this map contains no mapping for the key.
*
*
If the specified key is present in the map, the value data is read to the provided {@code
* value} object via value reader's {@link SizedReader#read(net.openhft.chronicle.bytes.Bytes, long, Object)
* read(StreamingDataInput, size, value)} method. If the value deserializer is able to reuse the
* given {@code value} object, calling this method instead of {@link #get(Object)} could help to
* reduce garbage creation.
*
*
The provided {@code value} object is allowed to be {@code null}, in this case {@code
* map.getUsing(key, null)} call is semantically equivalent to simple {@code map.get(key)}
* call.
*
* @param key the key whose associated value is to be returned
* @param usingValue the object to read value data in, if possible
* @return the value to which the specified key is mapped, or {@code null} if this map contains
* no mapping for the key
* @see #get(Object)
* @see #acquireUsing(Object, Object)
* @see ChronicleMapBuilder#valueMarshallers(SizedReader, SizedWriter)
*/
V getUsing(K key, V usingValue);
/**
* Acquire a value for a key, creating if absent.
*
*
If the specified key is absent in the map, {@linkplain
* ChronicleMapBuilder#defaultValueProvider(DefaultValueProvider) default value provider} is
* called. Then this object is put to this map for the specified key.
*
*
Then, either if the key was initially absent in the map or already present, the value is
* deserialized just as during {@link #getUsing(Object, Object) getUsing(key, usingValue)} call,
* passed the same {@code key} and {@code usingValue} as into this method call. This means, as
* in {@link #getUsing}, {@code usingValue} could safely be {@code null}, in this case a new
* value instance is created to deserialize the data.
*
*
In code, {@code acquireUsing} is specified as :
*
{@code
* V acquireUsing(K key, V usingValue) {
* if (!containsKey(key))
* put(key, defaultValue(key));
* return getUsing(key, usingValue);
* }}
*
*
*
Where {@code defaultValue(key)} returns {@link
* ChronicleMapBuilder#defaultValueProvider(DefaultValueProvider) defaultValueProvider}.
*
*
If the {@code ChronicleMap} is off-heap updatable, i. e. created via {@link
* ChronicleMapBuilder} builder (values are {@link Byteable}), there is one more option of what
* to do if the key is absent in the map. By default, value bytes are just zeroed out, no
* default value, either provided for key or constant, is put for the absent key.
*
* @param key the key whose associated value is to be returned
* @param usingValue the object to read value data in, if present. Can not be null
* @return value to which the given key is mapping after this call, either found or created
* @see #getUsing(Object, Object)
*/
V acquireUsing(@NotNull K key, V usingValue);
@NotNull
net.openhft.chronicle.core.io.Closeable acquireContext(@NotNull K key, @NotNull V usingValue);
/**
* Returns the result of application of the given function to the value to which the given key
* is mapped. If there is no mapping for the key, {@code null} is returned from {@code
* getMapped()} call without application of the given function. This method is primarily useful
* when accessing {@code ChronicleMap} implementation which delegates it's requests to some
* remote node (server) and pulls the result through serialization/deserialization path, and
* probably network. In this case, when you actually need only a part of the map value's state
* (e. g. a single field) it's cheaper to extract it on the server side and transmit lesser
* bytes.
*
* @param key the key whose associated value is to be queried
* @param function a function to transform the value to the actually needed result,
* which should be smaller than the map value
* @param the result type
* @return the result of applying the function to the mapped value, or {@code null} if there
* is no mapping for the key
*/
R getMapped(K key, @NotNull SerializableFunction function);
/**
* Exports all the entries to a {@link File} storing them in JSON format, an attempt is
* made where possible to use standard java serialisation and keep the data human readable, data
* serialized using the custom serialises are converted to a binary format which is not human
* readable but this is only done if the Keys or Values are not {@link Serializable}.
* This method can be used in conjunction with {@link ChronicleMap#putAll(File)} and is
* especially useful if you wish to import/export entries from one chronicle map into another.
* This import and export of the entries can be performed even when the versions of ChronicleMap
* differ. This method is not performant and as such we recommend it is not used in performance
* sensitive code.
*
* @param toFile the file to store all the entries to, the entries will be stored in JSON
* format
* @throws IOException its not possible store the data to {@code toFile}
* @see ChronicleMap#putAll(File)
*/
void getAll(File toFile) throws IOException;
/**
* Imports all the entries from a {@link File}, the {@code fromFile} must be created
* using or the same format as {@link ChronicleMap#get(Object)}, this method behaves
* similar to {@link Map#put(Object, Object)} where existing
* entries are overwritten. A write lock is only held while each individual entry is inserted
* into the map, not over all the entries in the {@link File}
*
* @param fromFile the file containing entries ( in JSON format ) which will be deserialized and
* {@link Map#put(Object, Object)} into the map
* @throws IOException its not possible read the {@code fromFile}
* @see ChronicleMap#getAll(File)
*/
void putAll(File fromFile) throws IOException;
/**
* @return the class of {@code }
*/
Class valueClass();
/**
* @return the value Class or UnresolvedType if unknown.
*/
Type valueType();
/**
* @return the amount of free space in the map as a percentage. When the free space gets low ( around 5% ) the map will automatically expand. The
* number of times it can automatically expand is based on the {@code net.openhft.chronicle.map.ChronicleMapBuilder#maxBloatFactor}. If the map
* expands you will see an increase in the available free space. NOTE: It is not possible to expand the chronicle map manually.
*
* see also {@see net.openhft.chronicle.map.ChronicleMap#remainingAutoResizes} as these operations are related.
*/
default short percentageFreeSpace() {
throw new UnsupportedOperationException("todo");
}
/**
* @return the number of times in the future the map can expand its capacity of each segment ( by expending its capacity we mean expending the maximum number of possible entries that
* can be stored into the map), the map will expand automatically. However, there is an upper limit to the number of times the map can expand.
* This limit is set via the {@code net.openhft.chronicle.map.ChronicleMapBuilder#maxBloatFactor} if the {@code remainingAutoResizes} drops to zero,
* then the map is no longer able to expand, if subsequently, the free space ( see {@link net.openhft.chronicle.map.ChronicleMap#percentageFreeSpace})
* in the map becomes low ( around 5% ), the map will not be able to take more entries and will fail with an {@code
* java.lang.IllegalStateException} for production systems it is recommended you periodically monitor the remainingAutoResizes and
* {@link net.openhft.chronicle.map.ChronicleMap#percentageFreeSpace}.
*/
default int remainingAutoResizes() {
throw new UnsupportedOperationException("todo");
}
}