All Downloads are FREE. Search and download functionalities are using the official Maven repository.

org.apache.cassandra.db.ReadExecutionController Maven / Gradle / Ivy

There is a newer version: 3.11.12.3
Show newest version
/*
 * 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.db;

import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.index.Index;
import org.apache.cassandra.utils.concurrent.OpOrder;

public class ReadExecutionController implements AutoCloseable
{
    // For every reads
    private final OpOrder.Group baseOp;
    private final CFMetaData baseMetadata; // kept to sanity check that we have take the op order on the right table

    // For index reads
    private final ReadExecutionController indexController;
    private final OpOrder.Group writeOp;

    private ReadExecutionController(OpOrder.Group baseOp, CFMetaData baseMetadata, ReadExecutionController indexController, OpOrder.Group writeOp)
    {
        // We can have baseOp == null, but only when empty() is called, in which case the controller will never really be used
        // (which validForReadOn should ensure). But if it's not null, we should have the proper metadata too.
        assert (baseOp == null) == (baseMetadata == null);
        this.baseOp = baseOp;
        this.baseMetadata = baseMetadata;
        this.indexController = indexController;
        this.writeOp = writeOp;
    }

    public ReadExecutionController indexReadController()
    {
        return indexController;
    }

    public OpOrder.Group writeOpOrderGroup()
    {
        return writeOp;
    }

    public boolean validForReadOn(ColumnFamilyStore cfs)
    {
        return baseOp != null && cfs.metadata.cfId.equals(baseMetadata.cfId);
    }

    public static ReadExecutionController empty()
    {
        return new ReadExecutionController(null, null, null, null);
    }

    /**
     * Creates an execution controller for the provided command.
     * 

* Note: no code should use this method outside of {@link ReadCommand#executionController} (for * consistency sake) and you should use that latter method if you need an execution controller. * * @param command the command for which to create a controller. * @return the created execution controller, which must always be closed. */ @SuppressWarnings("resource") // ops closed during controller close static ReadExecutionController forCommand(ReadCommand command) { ColumnFamilyStore baseCfs = Keyspace.openAndGetStore(command.metadata()); ColumnFamilyStore indexCfs = maybeGetIndexCfs(baseCfs, command); if (indexCfs == null) { return new ReadExecutionController(baseCfs.readOrdering.start(), baseCfs.metadata, null, null); } else { OpOrder.Group baseOp = null, writeOp = null; ReadExecutionController indexController = null; // OpOrder.start() shouldn't fail, but better safe than sorry. try { baseOp = baseCfs.readOrdering.start(); indexController = new ReadExecutionController(indexCfs.readOrdering.start(), indexCfs.metadata, null, null); // TODO: this should perhaps not open and maintain a writeOp for the full duration, but instead only *try* to delete stale entries, without blocking if there's no room // as it stands, we open a writeOp and keep it open for the duration to ensure that should this CF get flushed to make room we don't block the reclamation of any room being made writeOp = Keyspace.writeOrder.start(); return new ReadExecutionController(baseOp, baseCfs.metadata, indexController, writeOp); } catch (RuntimeException e) { // Note that must have writeOp == null since ReadOrderGroup ctor can't fail assert writeOp == null; try { if (baseOp != null) baseOp.close(); } finally { if (indexController != null) indexController.close(); } throw e; } } } private static ColumnFamilyStore maybeGetIndexCfs(ColumnFamilyStore baseCfs, ReadCommand command) { Index index = command.getIndex(baseCfs); return index == null ? null : index.getBackingTable().orElse(null); } public CFMetaData metaData() { return baseMetadata; } public void close() { try { if (baseOp != null) baseOp.close(); } finally { if (indexController != null) { try { indexController.close(); } finally { writeOp.close(); } } } } }





© 2015 - 2024 Weber Informatics LLC | Privacy Policy