com.datastax.oss.driver.internal.core.util.collection.QueryPlan Maven / Gradle / Ivy
/*
* 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,
* 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 com.datastax.oss.driver.internal.core.util.collection;
import com.datastax.oss.driver.api.core.metadata.Node;
import com.datastax.oss.driver.api.core.session.Request;
import com.datastax.oss.driver.api.core.session.Session;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.util.Iterator;
import java.util.Queue;
import net.jcip.annotations.ThreadSafe;
/**
* A specialized, thread-safe node queue for use when creating {@linkplain
* com.datastax.oss.driver.api.core.loadbalancing.LoadBalancingPolicy#newQueryPlan(Request, Session)
* query plans}.
*
* This interface and its built-in implementations are not general-purpose queues; they are
* tailored for the specific use case of creating query plans in the driver. They make a few
* unconventional API choices for the sake of performance.
*
*
Furthermore, the driver only consumes query plans through calls to its {@link #poll()} method;
* therefore, this method is the only valid mutation operation for a query plan, other mutating
* methods throw.
*
*
Both {@link #size()} and {@link #iterator()} are supported and never throw, even if called
* concurrently. These methods are implemented for reporting purposes only, the driver itself does
* not use them.
*
*
All built-in {@link QueryPlan} implementations can be safely reused for custom load balancing
* policies; if you plan to do so, study the source code of {@link
* com.datastax.oss.driver.internal.core.loadbalancing.DefaultLoadBalancingPolicy} or {@link
* com.datastax.oss.driver.internal.core.loadbalancing.BasicLoadBalancingPolicy}.
*
* @see QueryPlanBase
*/
@ThreadSafe
public interface QueryPlan extends Queue {
QueryPlan EMPTY = new EmptyQueryPlan();
/**
* {@inheritDoc}
*
* Implementation note: query plan iterators are snapshots that reflect the contents of the
* queue at the time of the call, and are not affected by further modifications. Successive calls
* to this method will return different objects.
*/
@NonNull
@Override
Iterator iterator();
@Override
default boolean offer(Node node) {
throw new UnsupportedOperationException("Not implemented");
}
@Override
default Node peek() {
throw new UnsupportedOperationException("Not implemented");
}
@Override
default boolean add(Node node) {
throw new UnsupportedOperationException("Not implemented");
}
@Override
default Node remove() {
throw new UnsupportedOperationException("Not implemented");
}
@Override
default Node element() {
throw new UnsupportedOperationException("Not implemented");
}
}