sijie commented on a change in pull request #1218: Support LacPiggyback,
LongPoll and ExplicitLac in db ledger storage
URL: https://github.com/apache/bookkeeper/pull/1218#discussion_r171256273
##########
File path:
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/storage/ldb/DbLedgerStorage.java
##########
@@ -74,10 +83,121 @@
*/
public class DbLedgerStorage implements CompactableLedgerStorage {
+ /**
+ * This class borrows the logic from FileInfo.
+ *
+ * <p>This class is used for holding all the transient states for a given
ledger.
+ */
+ private static class TransientLedgerInfo
+ extends Watchable<LastAddConfirmedUpdateNotification>
+ implements AutoCloseable {
+
+ // lac
+ private Long lac = null;
+ // request from explicit lac requests
+ private ByteBuffer explicitLac = null;
+ // is the ledger info closed?
+ private boolean isClosed;
+
+ private final long ledgerId;
+ // reference to LedgerMetadataIndex
+ private final LedgerMetadataIndex ledgerIndex;
+
+ /**
+ * Construct an Watchable with zero watchers.
+ */
+ public TransientLedgerInfo(long ledgerId, LedgerMetadataIndex
ledgerIndex) {
+ super(WATCHER_RECYCLER);
+ this.ledgerId = ledgerId;
+ this.ledgerIndex = ledgerIndex;
+ }
+
+ synchronized Long getLastAddConfirmed() {
+ return lac;
+ }
+
+ Long setLastAddConfirmed(long lac) {
+ long lacToReturn;
+ boolean changed = false;
+ synchronized (this) {
+ if (null == this.lac || this.lac < lac) {
+ this.lac = lac;
+ changed = true;
+ }
+ lacToReturn = this.lac;
+ }
+ if (changed) {
+ notifyWatchers(lacToReturn);
+ }
+ return lacToReturn;
+ }
+
+ synchronized boolean waitForLastAddConfirmedUpdate(long previousLAC,
+
Watcher<LastAddConfirmedUpdateNotification> watcher)
+ throws IOException {
+ if ((null != lac && lac > previousLAC)
+ || isClosed || ledgerIndex.get(ledgerId).getFenced()) {
+ return false;
+ }
+
+ addWatcher(watcher);
+ return true;
+ }
+
+ public ByteBuf getExplicitLac() {
+ ByteBuf retLac = null;
+ synchronized (this) {
+ if (explicitLac != null) {
+ retLac = Unpooled.buffer(explicitLac.capacity());
+ explicitLac.rewind(); //copy from the beginning
+ retLac.writeBytes(explicitLac);
+ explicitLac.rewind();
+ return retLac;
+ }
+ }
+ return retLac;
+ }
+
+ public void setExplicitLac(ByteBuf lac) {
+ long explicitLacValue;
+ synchronized (this) {
+ if (explicitLac == null) {
+ explicitLac = ByteBuffer.allocate(lac.capacity());
+ }
+ lac.readBytes(explicitLac);
+ explicitLac.rewind();
+
+ // skip the ledger id
+ explicitLac.getLong();
+ explicitLacValue = explicitLac.getLong();
+ explicitLac.rewind();
+ }
+ setLastAddConfirmed(explicitLacValue);
+ }
+
+ void notifyWatchers(long lastAddConfirmed) {
+ notifyWatchers(LastAddConfirmedUpdateNotification.FUNC,
lastAddConfirmed);
+ }
+
+ @Override
+ public void close() {
+ synchronized (this) {
+ if (isClosed) {
+ return;
+ }
+ isClosed = true;
+ }
+ // notify watchers
+ notifyWatchers(Long.MAX_VALUE);
Review comment:
we don't use the value notified as the source-of-truth. the value is used
for trigger the logic when the lac is changed. we re-read lac and put that
value in the response. we did this because LAC can potentially be updated
between the watcher received notification and sending the response. re-read
lac would give the most recent value, so the client can have as many entries to
read before hitting lac again.
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