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Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.
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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.kernel.info;

import java.lang.management.MemoryUsage;
import java.util.List;
import java.util.Locale;
import java.util.regex.Pattern;

import org.neo4j.logging.Log;

import static java.util.regex.Pattern.compile;
import static org.neo4j.configuration.BootloaderSettings.initial_heap_size;
import static org.neo4j.configuration.BootloaderSettings.max_heap_size;

public class JvmChecker
{
    private static final int SUPPORTED_FEATURE_VERSION = 11;
    static final String INCOMPATIBLE_JVM_WARNING = "You are using an unsupported Java runtime. Please" +
            " use Oracle(R) Java(TM) 11, OpenJDK(TM) 11.";
    static final String INCOMPATIBLE_JVM_VERSION_WARNING = "You are using an unsupported version of " +
            "the Java runtime. Please use Oracle(R) Java(TM) 11 or OpenJDK(TM) 11.";
    private static final Pattern SUPPORTED_JAVA_NAME_PATTERN = compile( "(Java HotSpot\\(TM\\)|OpenJDK) (64-Bit Server|Server) VM" );

    private final Log log;
    private final JvmMetadataRepository jvmMetadataRepository;

    public JvmChecker( Log log, JvmMetadataRepository jvmMetadataRepository )
    {
        this.log = log;
        this.jvmMetadataRepository = jvmMetadataRepository;
    }

    public void checkJvmCompatibilityAndIssueWarning()
    {
        String javaVmName = jvmMetadataRepository.getJavaVmName();
        Runtime.Version javaVersion = jvmMetadataRepository.getJavaVersion();

        if ( !SUPPORTED_JAVA_NAME_PATTERN.matcher( javaVmName ).matches() )
        {
            log.warn( INCOMPATIBLE_JVM_WARNING );
        }
        else if ( javaVersion.feature() != SUPPORTED_FEATURE_VERSION )
        {
            log.warn( INCOMPATIBLE_JVM_VERSION_WARNING );
        }
        List jvmArguments = jvmMetadataRepository.getJvmInputArguments();
        MemoryUsage heapMemoryUsage = jvmMetadataRepository.getHeapMemoryUsage();
        if ( missingOption( jvmArguments, "-Xmx" ) )
        {
            log.warn( maxMemorySettingWarning( heapMemoryUsage.getMax() ) );
        }
        if ( missingOption( jvmArguments, "-Xms" ) )
        {
            log.warn( initialMemorySettingWarning( heapMemoryUsage.getInit() ) );
        }
    }

    static String initialMemorySettingWarning( long currentUsage )
    {
        return String.format( "The initial heap memory has not been configured. It is recommended that it is always explicitly configured, to " +
                "ensure the system has a balanced configuration. Until then, a JVM computed heuristic of %d bytes is used instead. If you are running " +
                "neo4j server, you need to configure %s in neo4j.conf. If you are running neo4j embedded, you have to launch the JVM with -Xms set to a " +
                "value. You can run neo4j-admin memrec for memory configuration suggestions.", currentUsage, initial_heap_size.name() );
    }

    static String maxMemorySettingWarning( long currentUsage )
    {
        return String.format( "The max heap memory has not been configured. It is recommended that it is always explicitly configured, to " +
                "ensure the system has a balanced configuration. Until then, a JVM computed heuristic of %d bytes is used instead. If you are running " +
                "neo4j server, you need to configure %s in neo4j.conf. If you are running neo4j embedded, you have to launch the JVM with -Xmx set to a " +
                "value. You can run neo4j-admin memrec for memory configuration suggestions.", currentUsage, max_heap_size.name() );
    }

    private static boolean missingOption( List jvmArguments, String option )
    {
        String normalizedOption = option.toUpperCase( Locale.ROOT );
        return jvmArguments.stream().noneMatch( o -> o.toUpperCase( Locale.ROOT ).startsWith( normalizedOption ) );
    }
}