Mercurial > hg > blitz_stable
diff src/org/dancres/blitz/notify/SeqNumInterval.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/org/dancres/blitz/notify/SeqNumInterval.java Sat Mar 21 11:00:06 2009 +0000 @@ -0,0 +1,56 @@ +package org.dancres.blitz.notify; + +import java.io.IOException; +import java.io.Serializable; + +import java.util.logging.Level; + +import org.dancres.blitz.txn.TxnState; +import org.dancres.blitz.txn.TxnOp; + +import org.dancres.blitz.disk.DiskTxn; + +import org.dancres.blitz.oid.OID; + +import org.dancres.blitz.meta.RegistryFactory; +import org.dancres.blitz.meta.Registry; + +/** + Log action which restores a snapshotted sequence number to an event + generator. Rather than save an update to disk for each event we generate, + we log a single change record after a fixed number of events have been + dispatched. In this way, we reduce I/O's and can still keep the + EventGenerator sequence number up-to-date. Note that in the case of + restore from log, a <code>RemoteEventListener</code> will likely see a + slightly bigger jump than it might expect - that's okay. Note also that + such restarts will "eat up" a few sequence numbers (i.e. they will never + be used on a RemoteEvent) - that's okay too. + */ +class SeqNumInterval implements TxnOp { + private OID theOID; + private long theSeqNum; + + SeqNumInterval(OID aOID, long aSeqNum) { + theOID = aOID; + theSeqNum = aSeqNum; + } + + public void commit(TxnState aState) throws IOException { + // Nothing to do, we're just recording state + } + + public void abort(TxnState aState) throws IOException { + // Nothing to do, we're just recording state + } + + public void restore(TxnState aState) throws IOException { + EventQueue.theLogger.log(Level.FINE, "Patching notify reg" + + theOID + ", " + theSeqNum); + + EventGeneratorFactory.get().recover(theOID, theSeqNum); + } + + public String toString() { + return " SN : " + theOID + " : " + theSeqNum; + } +}