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DnsDiscovery: Rewrite to use better abstractions and remove some arbitrary magic numbers.

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Resolves issue 346.
This commit is contained in:
Mike Hearn
2013-03-29 18:18:45 +00:00
parent 08dbb21a39
commit 9e870f40bf
1 changed files with 35 additions and 43 deletions
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78
core/src/main/java/com/google/bitcoin/discovery/DnsDiscovery.java
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@@ -17,17 +17,13 @@
package com.google.bitcoin.discovery;
import com.google.bitcoin.core.NetworkParameters;
import com.google.common.collect.Sets;
import com.google.common.collect.Lists;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Set;
import java.util.*;
import java.util.concurrent.*;
/**
@@ -71,50 +67,46 @@ public class DnsDiscovery implements PeerDiscovery {
}
public InetSocketAddress[] getPeers(long timeoutValue, TimeUnit timeoutUnit) throws PeerDiscoveryException {
final BlockingQueue<InetSocketAddress> queue = new LinkedBlockingQueue<InetSocketAddress>();
ArrayList<String> seeds = new ArrayList<String>(Arrays.asList(hostNames));
// Java doesn't have an async DNS API so we have to do all lookups in a thread pool, as sometimes seeds go
// hard down and it takes ages to give up and move on.
ExecutorService pool = Executors.newFixedThreadPool(seeds.size());
for (final String seed : seeds) {
pool.submit(new Runnable() {
public void run() {
try {
InetAddress[] addrs = InetAddress.getAllByName(seed);
for (InetAddress addr : addrs) queue.put(new InetSocketAddress(addr, netParams.port));
} catch (UnknownHostException e) {
log.warn("Unable to resolve {}", seed);
} catch (InterruptedException e) {
// Silently go away.
ExecutorService threadPool = Executors.newFixedThreadPool(hostNames.length);
try {
List<Callable<InetAddress[]>> tasks = Lists.newArrayList();
for (final String seed : hostNames)
tasks.add(new Callable<InetAddress[]>() {
public InetAddress[] call() throws Exception {
return InetAddress.getAllByName(seed);
}
});
final List<Future<InetAddress[]>> futures = threadPool.invokeAll(tasks, timeoutValue, timeoutUnit);
ArrayList<InetSocketAddress> addrs = Lists.newArrayList();
for (int i = 0; i < futures.size(); i++) {
Future<InetAddress[]> future = futures.get(i);
if (future.isCancelled()) {
log.warn("{} timed out", hostNames[i]);
continue; // Timed out.
}
});
}
// The queue will fill up with resolutions. Let's wait until we got at least 30 or we run out of time.
final long timeout = timeoutUnit.toMillis(timeoutValue);
long start = System.currentTimeMillis();
Set<InetSocketAddress> addrs = Sets.newHashSet();
while (addrs.size() < 30) {
try {
long pollTime = timeout - (System.currentTimeMillis() - start);
if (pollTime < 0) break;
InetSocketAddress a = queue.poll(pollTime, TimeUnit.MILLISECONDS);
if (a == null) {
break;
final InetAddress[] inetAddresses;
try {
inetAddresses = future.get();
} catch (ExecutionException e) {
log.error("Failed to look up DNS seeds from {}: {}", hostNames[i], e.getMessage());
continue;
}
for (InetAddress addr : inetAddresses) {
addrs.add(new InetSocketAddress(addr, netParams.port));
}
addrs.add(a);
} catch (InterruptedException e) {
break;
}
if (addrs.size() == 0)
throw new PeerDiscoveryException("Unable to find any peers via DNS");
Collections.shuffle(addrs);
threadPool.shutdownNow();
return addrs.toArray(new InetSocketAddress[addrs.size()]);
} catch (InterruptedException e) {
throw new PeerDiscoveryException(e);
} finally {
threadPool.shutdown();
}
if (addrs.size() == 0) {
throw new PeerDiscoveryException("Unable to find any peers via DNS");
}
ArrayList<InetSocketAddress> shuffledAddrs = new ArrayList<InetSocketAddress>(addrs);
Collections.shuffle(shuffledAddrs);
pool.shutdown();
return shuffledAddrs.toArray(new InetSocketAddress[shuffledAddrs.size()]);
}
/** We don't have a way to abort a DNS lookup, so this does nothing */