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Refactored exponential backoff code out of JdbcDatabase and added tests.

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This commit is contained in:
akwizgran
2013-02-06 23:51:23 +00:00
parent 379d6ed220
commit 3af077a4d8
4 changed files with 96 additions and 13 deletions
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30
briar-core/src/net/sf/briar/db/ExponentialBackoff.java Normal file
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@@ -0,0 +1,30 @@
package net.sf.briar.db;
class ExponentialBackoff {
/**
* Returns the expiry time of a packet transmitted at time <tt>now</tt>
* over a transport with maximum latency <tt>maxLatency</tt>, where the
* packet has previously been transmitted <tt>txCount</tt> times. All times
* are in milliseconds. The expiry time is
* <tt>now + maxLatency * 2 ^ (txCount + 1)</tt>, so the interval between
* transmissions increases exponentially. If the expiry time would
* be greater than Long.MAX_VALUE, Long.MAX_VALUE is returned.
*/
static long calculateExpiry(long now, long maxLatency, int txCount) {
if(now < 0) throw new IllegalArgumentException();
if(maxLatency <= 0) throw new IllegalArgumentException();
if(txCount < 0) throw new IllegalArgumentException();
// The maximum round-trip time is twice the maximum latency
long roundTrip = maxLatency * 2;
if(roundTrip < 0) return Long.MAX_VALUE;
// The interval between transmissions is roundTrip * 2 ^ txCount
for(int i = 0; i < txCount; i++) {
roundTrip <<= 1;
if(roundTrip < 0) return Long.MAX_VALUE;
}
// The expiry time is the current time plus the interval
long expiry = now + roundTrip;
return expiry < 0 ? Long.MAX_VALUE : expiry;
}
}

14
briar-core/src/net/sf/briar/db/JdbcDatabase.java
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@@ -5,6 +5,7 @@ import static java.util.logging.Level.INFO;
import static java.util.logging.Level.WARNING;
import static net.sf.briar.api.Rating.UNRATED;
import static net.sf.briar.db.DatabaseConstants.RETENTION_MODULUS;
import static net.sf.briar.db.ExponentialBackoff.calculateExpiry;
import java.io.File;
import java.io.FileNotFoundException;
@@ -2877,17 +2878,4 @@ abstract class JdbcDatabase implements Database<Connection> {
throw new DbException(e);
}
}
// FIXME: Refactor the exponential backoff logic into a separate class
private long calculateExpiry(long now, long maxLatency, int txCount) {
long roundTrip = maxLatency * 2;
if(roundTrip < 0) return Long.MAX_VALUE;
for(int i = 0; i < txCount; i++) {
roundTrip <<= 1;
if(roundTrip < 0) return Long.MAX_VALUE;
}
long expiry = now + roundTrip;
if(expiry < 0) return Long.MAX_VALUE;
return expiry;
}
}