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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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 org.apache.cassandra.concurrent;
import io.netty.util.concurrent.FastThreadLocal;
import org.apache.cassandra.service.ClientWarn;
import org.apache.cassandra.tracing.TraceState;
import org.apache.cassandra.utils.Closeable;
import org.apache.cassandra.utils.WithResources;
/*
* This class only knows about Tracing and ClientWarn, so if any different executor locals are added, it must be
* updated.
*
* We don't enumerate the ExecutorLocal.all array each time because it would be much slower.
*/
public class ExecutorLocals implements WithResources, Closeable
{
private static final ExecutorLocals none = new ExecutorLocals(null, null);
private static final FastThreadLocal locals = new FastThreadLocal()
{
@Override
protected ExecutorLocals initialValue()
{
return none;
}
};
public static class Impl
{
protected static void set(TraceState traceState, ClientWarn.State clientWarnState)
{
if (traceState == null && clientWarnState == null) locals.set(none);
else locals.set(new ExecutorLocals(traceState, clientWarnState));
}
}
public final TraceState traceState;
public final ClientWarn.State clientWarnState;
protected ExecutorLocals(TraceState traceState, ClientWarn.State clientWarnState)
{
this.traceState = traceState;
this.clientWarnState = clientWarnState;
}
/**
* @return an ExecutorLocals object which has the current trace state and client warn state.
*/
public static ExecutorLocals current()
{
return locals.get();
}
/**
* The {@link #current}Locals, if any; otherwise {@link WithResources#none()}.
* Used to propagate current to other executors as a {@link WithResources}.
*/
public static WithResources propagate()
{
ExecutorLocals locals = current();
return locals == none ? WithResources.none() : locals;
}
public static ExecutorLocals create(TraceState traceState)
{
ExecutorLocals current = locals.get();
return current.traceState == traceState ? current : new ExecutorLocals(traceState, current.clientWarnState);
}
public static void clear()
{
locals.set(none);
}
/**
* Overwrite current locals, and return the previous ones
*/
public Closeable get()
{
ExecutorLocals old = current();
if (old != this)
locals.set(this);
return old;
}
public void close()
{
locals.set(this);
}
}