[ASTERIXDB-2497][TX] Ensure Log Record Flush LSN is Set

- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- Set the flush LSN of log records before giving it
  to the log flusher to avoid reading invalid value
  if the flush is completed before setting the LSN.
- Ensure log record LSN is thread-safe.
- Warn in case of a flush with LSN = 0.

Change-Id: Ifc605c2d794339a3dc5004b462eca50ec103c717
Reviewed-on: https://asterix-gerrit.ics.uci.edu/3087
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Murtadha Hubail <mhubail@apache.org>
Reviewed-by: Till Westmann <tillw@apache.org>

asterixdb/asterix-common/src/main/java/org/apache/asterix/common/context/PrimaryIndexOperationTracker.java

@@ -201,6 +201,9 @@ public synchronized void triggerScheduleFlush(LogRecord logRecord) throws Hyrack
             }
             idGenerator.refresh();
             long flushLsn = logRecord.getLSN();
+            if (flushLsn == 0) {
+                LOGGER.warn("flushing an index with LSN 0. Flush log record: {}", logRecord::getLogRecordForDisplay);
+            }
             ILSMComponentId nextComponentId = idGenerator.getId();
             Map<String, Object> flushMap = new HashMap<>();
             flushMap.put(LSMIOOperationCallback.KEY_FLUSH_LOG_LSN, flushLsn);

asterixdb/asterix-common/src/main/java/org/apache/asterix/common/transactions/LogRecord.java

@@ -88,7 +88,7 @@ public class LogRecord implements ILogRecord {
     private final ILogMarkerCallback callback; // A callback for log mark operations
     private int PKFieldCnt;
     private ITransactionContext txnCtx;
-    private long LSN;
+    private volatile long LSN;
     private final AtomicBoolean isFlushed;
     private final PrimaryKeyTupleReference readPKValue;
     private final SimpleTupleReference readNewValue;

asterixdb/asterix-transactions/src/main/java/org/apache/asterix/transaction/management/service/logging/LogManager.java

@@ -187,10 +187,10 @@ synchronized void syncAppendToLogTail(ILogRecord logRecord) {
         }
         final int logSize = logRecord.getLogSize();
         ensureSpace(logSize);
-        appendPage.append(logRecord, appendLSN.get());
         if (logRecord.getLogType() == LogType.FLUSH) {
             logRecord.setLSN(appendLSN.get());
         }
+        appendPage.append(logRecord, appendLSN.get());
         if (logRecord.isMarker()) {
             logRecord.logAppended(appendLSN.get());
         }