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package org.openslx.bwlp.sat;
import java.io.File;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.UUID;
import org.apache.commons.io.FileUtils;
import org.apache.log4j.Logger;
import org.openslx.bwlp.sat.util.Configuration;
import org.openslx.bwlp.sat.util.FileSystem;
import org.openslx.util.QuickTimer.Task;
/**
* As it might have catastrophic results if two instances of this server operate
* on the same file storage, we write a randomly generated id to a file on the
* storage, and check it periodically. If it changed, we bail out in complete
* panic.
*/
public class StorageUseCheck extends Task {
private static final Logger LOGGER = Logger.getLogger(StorageUseCheck.class);
private final String uuid = UUID.randomUUID().toString();
private final File canary = new File(Configuration.getVmStoreProdPath(), "dozmod.lock");
private boolean created = false;
public StorageUseCheck() {
if (FileSystem.waitForStorage()) {
createCanary();
}
}
private void createCanary() {
if (!FileSystem.isStorageMounted()) {
LOGGER.warn("Cannot check storage lock, storage not mounted");
return;
}
if (!created || !canary.exists()) {
try {
FileUtils.write(canary, uuid, StandardCharsets.UTF_8);
} catch (IOException e) {
LOGGER.fatal("Cannot write lock file to VMStore", e);
System.exit(1);
}
created = true;
} else {
String canaryContents;
try {
canaryContents = FileUtils.readFileToString(canary, StandardCharsets.UTF_8);
} catch (IOException e) {
LOGGER.warn("Lock file cannot be accessed. Cannot ensure exclusive use of VMStore", e);
return;
}
if (!canaryContents.equals(uuid)) {
LOGGER.fatal("Lock file content changed. Another server instance is using the VMStore."
+ " Will exit immediately to prevent any damages.");
try {
FileUtils.write(canary, uuid, StandardCharsets.UTF_8);
} catch (IOException e) {
}
System.exit(1);
}
}
}
@Override
public void fire() {
createCanary();
}
}
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