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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,
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* See the License for the specific language governing permissions and
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*/
package org.apache.cassandra.db.virtual;
import org.apache.cassandra.concurrent.DebuggableTask;
import org.apache.cassandra.concurrent.SharedExecutorPool;
import org.apache.cassandra.db.marshal.LongType;
import org.apache.cassandra.db.marshal.UTF8Type;
import org.apache.cassandra.dht.LocalPartitioner;
import org.apache.cassandra.schema.TableMetadata;
import static java.lang.Long.max;
import static java.util.concurrent.TimeUnit.NANOSECONDS;
import static org.apache.cassandra.utils.MonotonicClock.Global.approxTime;
/**
* Virtual table that lists currently running queries on the NTR (coordinator) and Read/Mutation (local) stages
*
* Example:
*
* cqlsh> SELECT * FROM system_views.queries;
*
* thread_id | queued_micros | running_micros | task
* ------------------------------+---------------+-----------------+--------------------------------------------------------------------------------
* Native-Transport-Requests-7 | 72923 | 7611 | QUERY select * from system_views.queries; [pageSize = 100]
* MutationStage-2 | 18249 | 2084 | Mutation(keyspace='distributed_test_keyspace', key='000000f8', modifications...
* ReadStage-2 | 72447 | 10121 | SELECT * FROM keyspace.table LIMIT 5000
*
*/
final class QueriesTable extends AbstractVirtualTable
{
private static final String TABLE_NAME = "queries";
private static final String ID = "thread_id";
private static final String QUEUED = "queued_micros";
private static final String RUNNING = "running_micros";
private static final String DESC = "task";
QueriesTable(String keyspace)
{
super(TableMetadata.builder(keyspace, TABLE_NAME)
.comment("Lists currently running queries")
.kind(TableMetadata.Kind.VIRTUAL)
.partitioner(new LocalPartitioner(UTF8Type.instance))
// The thread name is unique since the id given to each SEPWorker is unique
.addPartitionKeyColumn(ID, UTF8Type.instance)
.addRegularColumn(QUEUED, LongType.instance)
.addRegularColumn(RUNNING, LongType.instance)
.addRegularColumn(DESC, UTF8Type.instance)
.build());
}
/**
* Walks the {@link SharedExecutorPool} workers for any {@link DebuggableTask} instances and populates the table.
*/
@Override
public DataSet data()
{
SimpleDataSet result = new SimpleDataSet(metadata());
for (DebuggableTask.RunningDebuggableTask task : SharedExecutorPool.SHARED.runningTasks())
{
if (!task.hasTask()) continue;
long creationTimeNanos = task.creationTimeNanos();
long startTimeNanos = task.startTimeNanos();
long now = approxTime.now();
long queuedMicros = NANOSECONDS.toMicros(max((startTimeNanos > 0 ? startTimeNanos : now) - creationTimeNanos, 0));
long runningMicros = startTimeNanos > 0 ? NANOSECONDS.toMicros(now - startTimeNanos) : 0;
result.row(task.threadId())
.column(QUEUED, queuedMicros)
.column(RUNNING, runningMicros)
.column(DESC, task.description());
}
return result;
}
}