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// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hosted.node.admin.task.util.file;
import com.yahoo.vespa.hosted.node.admin.component.TaskContext;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.Optional;
import java.util.logging.Logger;
/**
* Class to minimize resource usage with repetitive and mostly identical, idempotent, and
* mutating file operations, e.g. setting file content, setting owner, etc.
*
* Only changes to the file is logged.
*
* @author hakohall
*/
// @ThreadUnsafe
public class FileSync {
private static final Logger logger = Logger.getLogger(FileSync.class.getName());
private final UnixPath path;
private final FileContentCache contentCache;
public FileSync(Path path) {
this.path = new UnixPath(path);
this.contentCache = new FileContentCache(this.path);
}
/**
* CPU, I/O, and memory usage is optimized for repeated calls with the same arguments.
* @return true if the system was modified: content was written, or owner was set, etc.
* system is only modified if necessary (different).
*/
public boolean convergeTo(TaskContext taskContext, PartialFileData partialFileData) {
FileAttributesCache currentAttributes = new FileAttributesCache(path);
boolean modifiedSystem = maybeUpdateContent(taskContext, partialFileData.getContent(), currentAttributes);
AttributeSync attributeSync = new AttributeSync(path.toPath()).with(partialFileData);
modifiedSystem |= attributeSync.converge(taskContext, currentAttributes);
return modifiedSystem;
}
private boolean maybeUpdateContent(TaskContext taskContext,
Optional<byte[]> content,
FileAttributesCache currentAttributes) {
if (!content.isPresent()) {
return false;
}
if (!currentAttributes.exists()) {
taskContext.recordSystemModification(logger, "Creating file " + path);
path.createParents();
path.writeBytes(content.get());
contentCache.updateWith(content.get(), currentAttributes.forceGet().lastModifiedTime());
return true;
}
if (Arrays.equals(content.get(), contentCache.get(currentAttributes.get().lastModifiedTime()))) {
return false;
} else {
taskContext.recordSystemModification(logger, "Patching file " + path);
path.writeBytes(content.get());
contentCache.updateWith(content.get(), currentAttributes.forceGet().lastModifiedTime());
return true;
}
}
}
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