co.elastic.apm.attach.CachedAttachmentProvider Maven / Gradle / Ivy
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* Licensed to Elasticsearch B.V. under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch B.V. 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 co.elastic.apm.attach;
import co.elastic.apm.attach.bytebuddy.agent.ByteBuddyAgent;
/**
* Successive attachments with a {@code tools.jar}-based {@link co.elastic.apm.attach.bytebuddy.agent.ByteBuddyAgent.AttachmentProvider}
* would lead to the {@link com.sun.tools.attach.VirtualMachine} class to be loaded from multiple class loaders
* (see {@link co.elastic.apm.attach.bytebuddy.agent.ByteBuddyAgent.AttachmentProvider.ForStandardToolsJarVm#attempt()}).
* That leads to a UnsatisfiedLinkError on Java 7 and 8 because the native library libattach can only be loaded by one class loader.
* By caching the {@link co.elastic.apm.attach.bytebuddy.agent.ByteBuddyAgent.AttachmentProvider.Accessor},
* the same VirtualMachine class is reused so that there is no attempt to load the libattach library from another class loader.
*/
public class CachedAttachmentProvider implements ByteBuddyAgent.AttachmentProvider {
private volatile Accessor accessor;
private final ByteBuddyAgent.AttachmentProvider delegate;
CachedAttachmentProvider(ByteBuddyAgent.AttachmentProvider delegate) {
this.accessor = delegate.attempt();
this.delegate = delegate;
}
@Override
public Accessor attempt() {
if (accessor == null) {
accessor = delegate.attempt();
}
return accessor;
}
}