zdm/envoy
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Add LocalDB Locking

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FIxes #32
This commit is contained in:
Kai S. K. Engelbart
2020-09-19 15:28:04 +02:00
parent 1ccf4354aa
commit fd21c5789f
2 changed files with 33 additions and 4 deletions
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26
client/src/main/java/envoy/client/data/LocalDB.java
View File

@@ -1,11 +1,14 @@
package envoy.client.data;
import java.io.*;
import java.nio.channels.*;
import java.nio.file.StandardOpenOption;
import java.time.Instant;
import java.util.*;
import envoy.data.*;
import envoy.event.*;
import envoy.exception.EnvoyException;
import envoy.util.SerializationUtils;
import dev.kske.eventbus.Event;
@@ -35,6 +38,7 @@ public final class LocalDB implements EventListener {
private Instant lastSync = Instant.EPOCH;
private String authToken;
private File dbDir, userFile, idGeneratorFile, lastLoginFile, usersFile;
private FileLock instanceLock;
/**
* Constructs an empty local database. To serialize any user-specific data to
@@ -74,6 +78,28 @@ public final class LocalDB implements EventListener {
userFile = new File(dbDir, user.getID() + ".db");
}
FileChannel fc;
/**
* Ensured that only one Envoy instance is using this local database by creating
* a lock file.
* The lock file is deleted on application exit.
*
* @throws EnvoyException if the lock cannot by acquired
* @since Envoy Client v0.2-beta
*/
public void lock() throws EnvoyException {
File file = new File(dbDir, "instance.lock");
file.deleteOnExit();
try {
FileChannel fc = FileChannel.open(file.toPath(), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
instanceLock = fc.tryLock();
if (instanceLock == null) throw new EnvoyException("Another Envoy instance is using this local database!");
} catch (IOException e) {
throw new EnvoyException("Could not create lock file!", e);
}
}
/**
* Stores all users. If the client user is specified, their chats will be stored
* as well. The message id generator will also be saved if present.

11
client/src/main/java/envoy/client/ui/Startup.java
View File

@@ -67,10 +67,13 @@ public final class Startup extends Application {
// Initialize the local database
try {
localDB = new LocalDB(new File(config.getHomeDirectory(), config.getLocalDB().getPath()));
} catch (final IOException e3) {
logger.log(Level.SEVERE, "Could not initialize local database: ", e3);
new Alert(AlertType.ERROR, "Could not initialize local database!\n" + e3).showAndWait();
File localDBDir = new File(config.getHomeDirectory(), config.getLocalDB().getPath());
logger.info("Initializing LocalDB at " + localDBDir);
localDB = new LocalDB(localDBDir);
localDB.lock();
} catch (IOException | EnvoyException e) {
logger.log(Level.SEVERE, "Could not initialize local database: ", e);
new Alert(AlertType.ERROR, "Could not initialize local database!\n" + e).showAndWait();
System.exit(1);
return;
}