Poison

jvm-profiler

发表于

最近在做 Java Agent 的相关开发，在查询相关开源 Java Agent 实现时想起了 Uber 的 jvm-profiler，之前在开发 Spark 相关应用时了解过该 Agent，最近处理 Java Agent 的类隔离又想起了它，于是看了看相关实现，其中 premain 方法的入口如下：

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/*
 * Copyright (c) 2018 Uber Technologies, Inc.
 *
 * Licensed 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.uber.profiling;

import java.lang.instrument.Instrumentation;

public final class Agent {

    private static AgentImpl agentImpl = new AgentImpl();

    private Agent() {
    }

    public static void agentmain(final String args, final Instrumentation instrumentation) {
        premain(args, instrumentation);
    }

    public static void premain(final String args, final Instrumentation instrumentation) {
        System.out.println("Java Agent " + AgentImpl.VERSION + " premain args: " + args);

        Arguments arguments = Arguments.parseArgs(args);
        arguments.runConfigProvider();
        agentImpl.run(arguments, instrumentation, null);
    }
}

其中 agentImpl.run 方法的实现见：AgentImpl.java，在入口处没有看见有创建独立的类加载器的相关逻辑，而在 pom.xml 中看到使用 maven-shade-plugin 对类进行了重定位，并未实现物理隔离。

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<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version>3.1.0</version>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>shade</goal>
            </goals>
            <configuration>
                <relocations>
                    <relocation>
                        <pattern>org.apache</pattern>
                        <shadedPattern>ujagent_shaded.org.apache</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.fasterxml</pattern>
                        <shadedPattern>ujagent_shaded.com.fasterxml</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>org.codehaus</pattern>
                        <shadedPattern>ujagent_shaded.org.codehaus</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.thoughtworks</pattern>
                        <shadedPattern>ujagent_shaded.com.thoughtworks</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>org.xerial</pattern>
                        <shadedPattern>ujagent_shaded.org.xerial</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>org.tukaani</pattern>
                        <shadedPattern>ujagent_shaded.org.tukaani</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>org.slf4j</pattern>
                        <shadedPattern>ujagent_shaded.org.slf4j</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.alibaba</pattern>
                        <shadedPattern>ujagent_shaded.com.alibaba</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>net.logstash</pattern>
                        <shadedPattern>ujagent_shaded.net.logstash</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.timgroup</pattern>
                        <shadedPattern>ujagent_shaded.com.timgroup</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.amazonaws</pattern>
                        <shadedPattern>ujagent_shaded.com.amazonaws</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>org.javassist</pattern>
                        <shadedPattern>ujagent_shaded.org.javassist</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>org.joda</pattern>
                        <shadedPattern>ujagent_shaded.org.joda</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>avro</pattern>
                        <shadedPattern>ujagent_shaded.avro</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>edu</pattern>
                        <shadedPattern>ujagent_shaded.edu</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>javassist</pattern>
                        <shadedPattern>ujagent_shaded.javassist</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>net</pattern>
                        <shadedPattern>ujagent_shaded.net</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.uber.data</pattern>
                        <shadedPattern>ujagent_shaded.com.uber.data</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.uber.m3</pattern>
                        <shadedPattern>ujagent_shaded.com.uber.m3</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.uber.stream</pattern>
                        <shadedPattern>ujagent_shaded.com.uber.stream</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.uber.elk</pattern>
                        <shadedPattern>ujagent_shaded.com.uber.elk</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>com.shade</pattern>
                        <shadedPattern>ujagent_shaded.com.shade</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>org.yaml</pattern>
                        <shadedPattern>ujagent_org.yaml</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>redis.clients</pattern>
                        <shadedPattern>ujagent_shaded.redis.clients</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>org.influxdb</pattern>
                        <shadedPattern>ujagent_shaded.org.influxdb</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>ch</pattern>
                        <shadedPattern>ujagent_shaded.ch</shadedPattern>
                    </relocation>
                    <relocation>
                        <pattern>okio</pattern>
                        <shadedPattern>ujagent_shaded.okio</shadedPattern>
                    </relocation>
                </relocations>
                <filters>
                    <filter>
                        <artifact>*:*</artifact>
                        <excludes>
                            <exclude>META-INF/maven/**</exclude>
                            <exclude>META-INF/services/com.fasterxml.**</exclude>
                            <exclude>META-INF/services/java.sql.Driver</exclude>
                            <exclude>awssdk_config_default.json</exclude>
                            <exclude>heatpipe.config.properties</exclude>
                            <exclude>log4j.properties</exclude>
                            <exclude>kafka/kafka-version.properties</exclude>
                            <exclude>darwin/x86_64/liblz4-java.dylib</exclude>
                            <exclude>linux/amd64/liblz4-java.so</exclude>
                            <exclude>linux/i386/liblz4-java.so</exclude>
                            <exclude>win32/amd64/liblz4-java.so</exclude>
                            <exclude>org/gjt/mm/mysql/**</exclude>
                        </excludes>
                    </filter>
                </filters>
            </configuration>
        </execution>
    </executions>
</plugin>
Reference

JVM Profiler: An Open Source Tool for Tracing Distributed JVM Applications at Scale