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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.kafka.streams;
import org.apache.kafka.streams.processor.TopicNameExtractor;
import org.apache.kafka.streams.processor.internals.StreamTask;
import java.util.Set;
import java.util.regex.Pattern;
/**
* A meta representation of a {@link Topology topology}.
*
* The nodes of a topology are grouped into {@link Subtopology sub-topologies} if they are connected.
* In contrast, two sub-topologies are not connected but can be linked to each other via topics, i.e., if one
* sub-topology {@link Topology#addSink(String, String, String...) writes} into a topic and another sub-topology
* {@link Topology#addSource(String, String...) reads} from the same topic.
*
* When {@link KafkaStreams#start()} is called, different sub-topologies will be constructed and executed as independent
* {@link StreamTask tasks}.
*/
public interface TopologyDescription {
/**
* A connected sub-graph of a {@link Topology}.
*
* Nodes of a {@code Subtopology} are connected {@link Topology#addProcessor(String,
* org.apache.kafka.streams.processor.ProcessorSupplier, String...) directly} or indirectly via
* {@link Topology#connectProcessorAndStateStores(String, String...) state stores}
* (i.e., if multiple processors share the same state).
*/
interface Subtopology {
/**
* Internally assigned unique ID.
* @return the ID of the sub-topology
*/
int id();
/**
* All nodes of this sub-topology.
* @return set of all nodes within the sub-topology
*/
Set nodes();
}
/**
* Represents a {@link Topology#addGlobalStore(org.apache.kafka.streams.state.StoreBuilder, String,
* org.apache.kafka.common.serialization.Deserializer, org.apache.kafka.common.serialization.Deserializer, String,
* String, org.apache.kafka.streams.processor.ProcessorSupplier) global store}.
* Adding a global store results in adding a source node and one stateful processor node.
* Note, that all added global stores form a single unit (similar to a {@link Subtopology}) even if different
* global stores are not connected to each other.
* Furthermore, global stores are available to all processors without connecting them explicitly, and thus global
* stores will never be part of any {@link Subtopology}.
*/
interface GlobalStore {
/**
* The source node reading from a "global" topic.
* @return the "global" source node
*/
Source source();
/**
* The processor node maintaining the global store.
* @return the "global" processor node
*/
Processor processor();
int id();
}
/**
* A node of a topology. Can be a source, sink, or processor node.
*/
interface Node {
/**
* The name of the node. Will never be {@code null}.
* @return the name of the node
*/
String name();
/**
* The predecessors of this node within a sub-topology.
* Note, sources do not have any predecessors.
* Will never be {@code null}.
* @return set of all predecessors
*/
Set predecessors();
/**
* The successor of this node within a sub-topology.
* Note, sinks do not have any successors.
* Will never be {@code null}.
* @return set of all successor
*/
Set successors();
}
/**
* A source node of a topology.
*/
interface Source extends Node {
/**
* The topic names this source node is reading from.
* @return comma separated list of topic names or pattern (as String)
* @deprecated use {@link #topicSet()} or {@link #topicPattern()} instead
*/
@Deprecated
String topics();
/**
* The topic names this source node is reading from.
* @return a set of topic names
*/
Set topicSet();
/**
* The pattern used to match topic names that is reading from.
* @return the pattern used to match topic names
*/
Pattern topicPattern();
}
/**
* A processor node of a topology.
*/
interface Processor extends Node {
/**
* The names of all connected stores.
* @return set of store names
*/
Set stores();
}
/**
* A sink node of a topology.
*/
interface Sink extends Node {
/**
* The topic name this sink node is writing to.
* Could be {@code null} if the topic name can only be dynamically determined based on {@link TopicNameExtractor}
* @return a topic name
*/
String topic();
/**
* The {@link TopicNameExtractor} class that this sink node uses to dynamically extract the topic name to write to.
* Could be {@code null} if the topic name is not dynamically determined.
* @return the {@link TopicNameExtractor} class used get the topic name
*/
TopicNameExtractor topicNameExtractor();
}
/**
* All sub-topologies of the represented topology.
* @return set of all sub-topologies
*/
Set subtopologies();
/**
* All global stores of the represented topology.
* @return set of all global stores
*/
Set globalStores();
}