Change summary
src/main/java/de/measite/minidns/Client.java | 86 ++----------
src/main/java/de/measite/minidns/DNSCache.java | 12 +
src/main/java/de/measite/minidns/LRUCache.java | 139 ++++++++++++++++++++
3 files changed, 165 insertions(+), 72 deletions(-)
Detailed changes
@@ -13,8 +13,6 @@ import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
-import java.util.LinkedHashMap;
-import java.util.Map.Entry;
import java.util.Random;
import java.util.logging.Level;
import java.util.logging.Logger;
@@ -48,23 +46,26 @@ public class Client {
/**
* The internal DNS cache.
*/
- protected LinkedHashMap<Question, DNSMessage> cache;
+ protected DNSCache cache;
/**
- * Maximum acceptable ttl.
+ * Create a new DNS client with the given DNS cache.
+ * @param cache The backend DNS cache.
*/
- protected long maxTTL = 60 * 60 * 1000;
-
- /**
- * Create a new DNS client.
- */
- public Client() {
+ public Client(DNSCache cache) {
try {
random = SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e1) {
random = new SecureRandom();
}
- setCacheSize(10);
+ this.cache = cache;
+ }
+
+ /**
+ * Create a new DNS client.
+ */
+ public Client() {
+ this(null);
}
/**
@@ -132,19 +133,8 @@ public class Client {
*/
public DNSMessage query(Question q, String host, int port) throws IOException {
DNSMessage dnsMessage = (cache == null) ? null : cache.get(q);
- if (dnsMessage != null && dnsMessage.getReceiveTimestamp() > 0l) {
- // check the ttl
- long ttl = maxTTL;
- for (Record r : dnsMessage.getAnswers()) {
- ttl = Math.min(ttl, r.ttl);
- }
- for (Record r : dnsMessage.getAdditionalResourceRecords()) {
- ttl = Math.min(ttl, r.ttl);
- }
- if (dnsMessage.getReceiveTimestamp() + ttl <
- System.currentTimeMillis()) {
- return dnsMessage;
- }
+ if (dnsMessage != null) {
+ return dnsMessage;
}
DNSMessage message = new DNSMessage();
message.setQuestions(new Question[]{q});
@@ -326,52 +316,4 @@ public class Client {
return null;
}
- /**
- * Configure the cache size (default 10).
- * @param maximumSize The new cache size or 0 to disable.
- */
- @SuppressWarnings("serial")
- public void setCacheSize(final int maximumSize) {
- if (maximumSize == 0) {
- this.cache = null;
- } else {
- LinkedHashMap<Question,DNSMessage> old = cache;
- cache = new LinkedHashMap<Question,DNSMessage>() {
- @Override
- protected boolean removeEldestEntry(
- Entry<Question, DNSMessage> eldest) {
- return size() > maximumSize;
- }
- };
- if (old != null) {
- cache.putAll(old);
- }
- }
- }
-
- /**
- * Flush the DNS cache.
- */
- public void flushCache() {
- if (cache != null) {
- cache.clear();
- }
- }
-
- /**
- * Get the current maximum record ttl.
- * @return The maximum record ttl.
- */
- public long getMaxTTL() {
- return maxTTL;
- }
-
- /**
- * Set the maximum record ttl.
- * @param maxTTL The new maximum ttl.
- */
- public void setMaxTTL(long maxTTL) {
- this.maxTTL = maxTTL;
- }
-
}
@@ -0,0 +1,12 @@
+package de.measite.minidns;
+
+/**
+ * Cache for DNS Entries. Implementations must be thread safe.
+ */
+public interface DNSCache {
+
+ void put(Question q, DNSMessage message);
+
+ DNSMessage get(Question q);
+
+}
@@ -0,0 +1,139 @@
+package de.measite.minidns;
+
+import java.util.LinkedHashMap;
+import java.util.Map.Entry;
+
+/**
+ * LRU based DNSCache backed by a LinkedHashMap.
+ */
+public class LRUCache implements DNSCache {
+
+ /**
+ * Internal miss count.
+ */
+ protected long missCount = 0l;
+
+ /**
+ * Internal expire count (subset of misses that was caused by expire).
+ */
+ protected long expireCount = 0l;
+
+ /**
+ * Internal hit count.
+ */
+ protected long hitCount = 0l;
+
+ /**
+ * The internal capacity of the backend cache.
+ */
+ protected int capacity;
+
+ /**
+ * The upper bound of the ttl. All longer TTLs will be capped by this ttl.
+ */
+ protected long maxTTL;
+
+ /**
+ * The backend cache.
+ */
+ protected LinkedHashMap<Question, DNSMessage> backend;
+
+ /**
+ * Create a new LRUCache with given capacity and upper bound ttl.
+ * @param capacity The internal capacity.
+ * @param maxTTL The upper bound for any ttl.
+ */
+ @SuppressWarnings("serial")
+ public LRUCache(final int capacity, final long maxTTL) {
+ this.capacity = capacity;
+ this.maxTTL = maxTTL;
+ backend = new LinkedHashMap<Question,DNSMessage>(
+ Math.min(capacity, 11), 0.75f, true)
+ {
+ @Override
+ protected boolean removeEldestEntry(
+ Entry<Question, DNSMessage> eldest) {
+ return size() > capacity;
+ }
+ };
+ }
+
+ /**
+ * Create a new LRUCache with given capacity.
+ * @param capacity
+ */
+ public LRUCache(final int capacity) {
+ this(capacity, Long.MAX_VALUE);
+ }
+
+ @Override
+ public synchronized void put(Question q, DNSMessage message) {
+ if (message.getReceiveTimestamp() <= 0l) {
+ return;
+ }
+ backend.put(q, message);
+ }
+
+ @Override
+ public synchronized DNSMessage get(Question q) {
+ DNSMessage message = backend.get(q);
+ if (message == null) {
+ missCount++;
+ return null;
+ }
+
+ long ttl = maxTTL;
+ for (Record r : message.getAnswers()) {
+ ttl = Math.min(ttl, r.ttl);
+ }
+ for (Record r : message.getAdditionalResourceRecords()) {
+ ttl = Math.min(ttl, r.ttl);
+ }
+ if (message.getReceiveTimestamp() + ttl > System.currentTimeMillis()) {
+ missCount++;
+ expireCount++;
+ backend.remove(q);
+ return null;
+ } else {
+ hitCount++;
+ return message;
+ }
+ }
+
+ /**
+ * Clear all entries in this cache.
+ */
+ public synchronized void clear() {
+ backend.clear();
+ missCount = 0l;
+ hitCount = 0l;
+ expireCount = 0l;
+ }
+
+ /**
+ * Get the miss count of this cache which is the number of fruitless
+ * get calls since this cache was last resetted.
+ * @return The number of cache misses.
+ */
+ public long getMissCount() {
+ return missCount;
+ }
+
+ /**
+ * The number of expires (cache hits that have had a ttl to low to be
+ * retrieved).
+ * @return The expire count.
+ */
+ public long getExpireCount() {
+ return expireCount;
+ }
+
+ /**
+ * The cache hit count (all sucessful calls to get).
+ * @return The hit count.
+ */
+ public long getHitCount() {
+ return hitCount;
+ }
+
+}