DNS (ticket #1998):

- Data: Cache hostname lookups in RouterAddress
- Job Queue: Make search jobs droppable
- Router: Increase JVM DNS cache time
- Util: Add negative DNS lookup cache, increase cache size

router/java/src/net/i2p/data/router/RouterAddress.java

@@ -50,11 +50,12 @@ public class RouterAddress extends DataStructureImpl {
     private String _transportStyle;
     private final Properties _options;
     // cached values
-    private byte[] _ip;
+    private byte[] _ip = NOT_LOOKED_UP;
     private int _port;
 
     public static final String PROP_HOST = "host";
     public static final String PROP_PORT = "port";
+    private static final byte[] NOT_LOOKED_UP = new byte[0];
 
     public RouterAddress() {
         _options = new OrderedProperties();
@@ -213,26 +214,23 @@ public class RouterAddress extends DataStructureImpl {
     
     /**
      *  Caching version of InetAddress.getByName(getOption("host")).getAddress(), which is slow.
-     *  Caches numeric host names only.
-     *  Will resolve but not cache resolution of DNS host names.
+     *  Caches numeric host names AND DNS host names, and negative caches also.
      *
      *  @return IP or null
      *  @since 0.9.3
      */
-    public byte[] getIP() {
-        if (_ip != null)
-            return _ip;
-        byte[] rv = null;
-        String host = getHost();
-        if (host != null) {
-            rv = Addresses.getIP(host);
-            if (rv != null &&
-                (InetAddressUtils.isIPv4Address(host) ||
-                 InetAddressUtils.isIPv6Address(host))) {
-                _ip = rv;
-            }
+    public synchronized byte[] getIP() {
+        if (_ip == NOT_LOOKED_UP) {
+            // Only look up once, even if it fails, so we don't generate excessive DNS lookups.
+            // The lifetime of a RouterAddress object is a few hours at most,
+            // it will get republished or expired, so it's OK even for host names.
+            String host = getHost();
+            if (host != null)
+                _ip = Addresses.getIP(host);
+            else
+                _ip = null;
         }
-        return rv;
+        return _ip;
     }
     
     /**

router/java/src/net/i2p/router/JobQueue.java

@@ -27,6 +27,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 import net.i2p.data.DataHelper;
 import net.i2p.router.message.HandleGarlicMessageJob;
 import net.i2p.router.networkdb.kademlia.HandleFloodfillDatabaseLookupMessageJob;
+import net.i2p.router.networkdb.kademlia.IterativeSearchJob;
 import net.i2p.router.RouterClock;
 import net.i2p.util.Clock;
 import net.i2p.util.I2PThread;
@@ -316,10 +317,13 @@ public class JobQueue {
             // Garlic added in 0.9.19, floodfills were getting overloaded
             // with encrypted lookups
             //
+            // ISJ added in 0.9.31, can get backed up due to DNS
+            //
             // Obviously we can only drop one-shot jobs, not those that requeue
             //
             if (cls == HandleFloodfillDatabaseLookupMessageJob.class ||
-                cls == HandleGarlicMessageJob.class) {
+                cls == HandleGarlicMessageJob.class ||
+                cls == IterativeSearchJob.class) {
                 // this tail drops based on the lag at the tail, which
                 // makes no sense...
                 //JobTiming jt = job.getTiming();

router/java/src/net/i2p/router/Router.java

@@ -117,7 +117,6 @@ public class Router implements RouterClock.ClockShiftListener {
     private final static String PROP_SHUTDOWN_IN_PROGRESS = "__shutdownInProgress";
     public static final String PROP_IB_RANDOM_KEY = TunnelPoolSettings.PREFIX_INBOUND_EXPLORATORY + TunnelPoolSettings.PROP_RANDOM_KEY;
     public static final String PROP_OB_RANDOM_KEY = TunnelPoolSettings.PREFIX_OUTBOUND_EXPLORATORY + TunnelPoolSettings.PROP_RANDOM_KEY;
-    private final static String DNS_CACHE_TIME = "" + (5*60);
     private static final String EVENTLOG = "eventlog.txt";
     private static final String PROP_JBIGI = "jbigi.loadedResource";
     public static final String UPDATE_FILE = "i2pupdate.zip";
@@ -133,10 +132,12 @@ public class Router implements RouterClock.ClockShiftListener {
         if (System.getProperty("I2P_DISABLE_DNS_CACHE_OVERRIDE") == null) {
             // grumble about sun's java caching DNS entries *forever* by default
             // so lets just keep 'em for a short time
+            String DNS_CACHE_TIME = Integer.toString(2*60*60);
+            String DNS_NEG_CACHE_TIME = Integer.toString(30*60);
             System.setProperty("sun.net.inetaddr.ttl", DNS_CACHE_TIME);
-            System.setProperty("sun.net.inetaddr.negative.ttl", DNS_CACHE_TIME);
+            System.setProperty("sun.net.inetaddr.negative.ttl", DNS_NEG_CACHE_TIME);
             System.setProperty("networkaddress.cache.ttl", DNS_CACHE_TIME);
-            System.setProperty("networkaddress.cache.negative.ttl", DNS_CACHE_TIME);
+            System.setProperty("networkaddress.cache.negative.ttl", DNS_NEG_CACHE_TIME);
         }
         if (System.getProperty("I2P_DISABLE_HTTP_AGENT_OVERRIDE") == null) {
             System.setProperty("http.agent", "I2P");

router/java/src/net/i2p/router/RouterVersion.java

@@ -18,7 +18,7 @@ public class RouterVersion {
     /** deprecated */
     public final static String ID = "Monotone";
     public final static String VERSION = CoreVersion.VERSION;
-    public final static long BUILD = 11;
+    public final static long BUILD = 12;
 
     /** for example "-test" */
     public final static String EXTRA = "";

router/java/src/net/i2p/router/networkdb/kademlia/IterativeSearchJob.java

@@ -54,9 +54,11 @@ import net.i2p.util.VersionComparator;
  * Halves search traffic for successful searches, as this doesn't do
  * two sesarches in parallel like FOSJ does.
  *
+ * Public only for JobQueue, not a public API, not for external use.
+ *
  * @since 0.8.9
  */
-class IterativeSearchJob extends FloodSearchJob {
+public class IterativeSearchJob extends FloodSearchJob {
     /** peers not sent to yet, sorted closest-to-the-routing-key */
     private final SortedSet<Hash> _toTry;
     /** query sent, no reply yet */
@@ -559,6 +561,15 @@ class IterativeSearchJob extends FloodSearchJob {
         return rv == null ? -1 : rv.longValue();
     }
 
+    /**
+     *  Dropped by the job queue
+     *  @since 0.9.31
+     */
+    @Override
+    public void dropped() {
+        failed();
+    }
+
     /**
      *  Total failure
      */