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package org.dcache.resilience.util;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingDeque;
import diskCacheV111.util.PnfsId;
import diskCacheV111.vehicles.Message;
import diskCacheV111.vehicles.PnfsAddCacheLocationMessage;
import diskCacheV111.vehicles.PnfsClearCacheLocationMessage;
import org.dcache.resilience.handlers.ResilienceMessageHandler;
import org.dcache.vehicles.CorruptFileMessage;
/**
* <p>Persists backlogged messages to a file. When reactivated, the
* file is read back in and the messages sent back to the
* {@link ResilienceMessageHandler}.</p>
*
* <p>Pool-based messages are not saved.</p>
*
* <p>File is deleted after reload.</p>
*/
public final class SimplePersistentBacklogHandler
implements BackloggedMessageHandler {
private static final Logger LOGGER = LoggerFactory.getLogger(
SimplePersistentBacklogHandler.class);
abstract class BacklogThread implements Runnable {
private Thread thread;
protected void start() {
if (thread == null || !thread.isAlive()) {
thread = new Thread(this, this.getClass().getSimpleName());
thread.start();
}
}
protected void stop() {
if (thread != null && thread.isAlive()) {
thread.interrupt();
try {
thread.join();
} catch (InterruptedException e) {
// ignore
}
}
thread = null;
}
}
class Consumer extends BacklogThread {
private PrintWriter pw;
@Override
public void run() {
while (!Thread.interrupted()) {
try {
Collection<Serializable> data = new ArrayList<>();
/*
* take blocks until non-empty; it is synchronized
*/
data.add(queue.take());
queue.drainTo(data, 1000);
data.stream().forEach(this::saveToBacklog);
} catch (InterruptedException ignored) {
break;
}
}
LOGGER.info("Backlogged messages consumer exiting.");
}
protected void start() {
try {
pw = new PrintWriter(new FileWriter(backlogStore, true));
} catch (IOException e) {
LOGGER.info("Failed to open writer to save "
+ "backlogged messages: {}.",
new ExceptionMessage(e));
return;
}
super.start();
}
protected void stop() {
super.stop();
pw.close();
}
/**
* <p>Only file operation messages are stored.</p>
*/
private void saveToBacklog(Serializable message) {
String pnfsid;
String pool;
String type;
if (message instanceof CorruptFileMessage) {
CorruptFileMessage specific = (CorruptFileMessage) message;
pnfsid = specific.getPnfsId().toString();
pool = specific.getPool();
type = CorruptFileMessage.class.getSimpleName();
} else if (message instanceof PnfsClearCacheLocationMessage) {
PnfsClearCacheLocationMessage specific
= (PnfsClearCacheLocationMessage) message;
pnfsid = specific.getPnfsId().toString();
pool = specific.getPoolName();
type = PnfsClearCacheLocationMessage.class.getSimpleName();
} else if (message instanceof PnfsAddCacheLocationMessage) {
PnfsAddCacheLocationMessage specific
= (PnfsAddCacheLocationMessage) message;
pnfsid = specific.getPnfsId().toString();
pool = specific.getPoolName();
type = PnfsAddCacheLocationMessage.class.getSimpleName();
} else {
return;
}
pw.println(type + "," + pnfsid + "," + pool);
if (pw.checkError()) {
LOGGER.error("Problem saving ({} {} {}) to file; skipped.",
type, pnfsid, pool);
}
}
}
class Reloader extends BacklogThread {
@Override
public void run() {
if (!backlogStore.exists()) {
return;
}
try (BufferedReader fr
= new BufferedReader(new FileReader(backlogStore))) {
while (!Thread.interrupted()) {
String line = fr.readLine();
if (line == null) {
break;
}
try {
messageHandler.processBackloggedMessage(fromString(line));
} catch (IllegalStateException e) {
LOGGER.debug("Unable to reload message; {}",
e.getMessage());
}
}
backlogStore.delete();
} catch (FileNotFoundException e) {
LOGGER.error("Unable to reload checkpoint file: {}",
e.getMessage());
} catch (IOException e) {
LOGGER.error("Unrecoverable error during reload checkpoint file: {}",
e.getMessage());
}
LOGGER.info("Done reloading backlogged messages.");
}
}
private static Message fromString(String line) {
String[] parts = line.split("[,]");
if (parts.length != 3) {
throw new IllegalStateException(line + " is malformed.");
}
if (parts[0].equals(CorruptFileMessage.class.getSimpleName())) {
return new CorruptFileMessage(parts[2], new PnfsId(parts[1]));
} else if (parts[0].equals(
PnfsClearCacheLocationMessage.class.getSimpleName())) {
return new PnfsClearCacheLocationMessage(new PnfsId(parts[1]),
parts[2]);
} else if (parts[0].equals(
PnfsAddCacheLocationMessage.class.getSimpleName())) {
return new PnfsAddCacheLocationMessage(new PnfsId(parts[1]),
parts[2]);
} else {
throw new IllegalStateException(line + ": invalid message type.");
}
}
BlockingQueue<Serializable> queue;
ResilienceMessageHandler messageHandler;
private final File backlogStore;
private final Consumer consumer;
private final Reloader reloader;
public SimplePersistentBacklogHandler(String path) {
backlogStore = new File(path);
consumer = new Consumer();
reloader = new Reloader();
/*
* Set the max fairly high. File write should not take
* that long.
*/
queue = new LinkedBlockingDeque<>(1000000);
}
@Override
public void handleBacklog() {
consumer.stop();
reloader.start();
}
@Override
public void initialize() {
consumer.start();
}
@Override
public void saveToBacklog(Serializable message) {
try {
queue.put(message);
} catch (InterruptedException t) {
LOGGER.info("Queue limit reached, dropping {}.", message);
}
}
public void setMessageHandler(ResilienceMessageHandler messageHandler) {
this.messageHandler = messageHandler;
}
@Override
public void shutdown() {
queue.clear();
consumer.stop();
reloader.stop();
}
}