Don't trust the cached last sequence header. Fixes #1538

src/main/java/net/openhft/chronicle/queue/ExcerptTailer.java

@@ -232,11 +232,12 @@ default boolean readAfterReplicaAcknowledged() {
      * Calling this method may move ExcerptTailer to the specified cycle and release its store.
      *
      * @return the approximate number of excerpts in a cycle.
+     *
+     * @deprecated Use {@link #excerptsInCycle(int)} instead
      */
+    @Deprecated(/* To be removed in x.27 */)
     default long approximateExcerptsInCycle(int cycle) {
-        try (ExcerptTailer tailer = queue().createTailer()) {
-            return tailer.approximateExcerptsInCycle(cycle);
-        }
+        return excerptsInCycle(cycle);
     }
 
     /**
@@ -246,10 +247,24 @@ default long approximateExcerptsInCycle(int cycle) {
      * Calling this method may move ExcerptTailer to the specified cycle and release its store.
      *
      * @return the exact number of excerpts in a cycle.
+     *
+     * @deprecated Use {@link #excerptsInCycle(int)} instead
      */
+    @Deprecated(/* To be removed in x.27 */)
     default long exactExcerptsInCycle(int cycle) {
+        return excerptsInCycle(cycle);
+    }
+
+    /**
+     * Return the exact number of excerpts in a cycle available for reading.
+     * <p>
+     * Calling this method may move ExcerptTailer to the specified cycle and release its store.
+     *
+     * @return the exact number of excerpts in a cycle.
+     */
+    default long excerptsInCycle(int cycle) {
         try (ExcerptTailer tailer = queue().createTailer()) {
-            return tailer.exactExcerptsInCycle(cycle);
+            return tailer.excerptsInCycle(cycle);
         }
     }
 

src/main/java/net/openhft/chronicle/queue/QueueSystemProperties.java

@@ -35,7 +35,7 @@ private QueueSystemProperties() {
      * Default unset value: false
      * Activation values  : "", "yes", or "true"
      */
-    public static final boolean CHECK_INDEX = Jvm.getBoolean("queue.check.index");
+    public static boolean CHECK_INDEX = Jvm.getBoolean("queue.check.index");
 
     /**
      * Name of a system property used to specify the default roll cycle.

src/main/java/net/openhft/chronicle/queue/impl/single/BinarySearch.java

@@ -141,7 +141,7 @@ public static long findWithinCycle(@NotNull Wire key,
         try {
             long lowSeqNum = 0;
 
-            long highSeqNum = tailer.approximateExcerptsInCycle(cycle) - 1;
+            long highSeqNum = tailer.excerptsInCycle(cycle) - 1;
 
             // nothing to search
             if (highSeqNum < lowSeqNum)

src/main/java/net/openhft/chronicle/queue/impl/single/SCQIndexing.java

@@ -38,6 +38,7 @@
 
 import java.io.EOFException;
 import java.io.StreamCorruptedException;
+import java.io.UncheckedIOException;
 import java.lang.ref.WeakReference;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -574,7 +575,7 @@ long sequenceForPosition(@NotNull ExcerptContext ec,
         try {
             return linearScanByPosition(wire, position, indexOfNext, lastKnownAddress, inclusive);
         } catch (EOFException e) {
-            throw new IllegalStateException(e);
+            throw new UncheckedIOException(e);
         }
     }
 
@@ -705,12 +706,12 @@ public boolean indexable(long index) {
         return (index & (indexSpacing - 1)) == 0;
     }
 
-    public long lastSequenceNumber(@NotNull ExcerptContext ec, boolean approximate)
+    public long lastSequenceNumber(@NotNull ExcerptContext ec)
             throws StreamCorruptedException {
         throwExceptionIfClosed();
 
         Sequence sequence1 = this.sequence;
-        if (approximate && sequence1 != null) {
+        if (sequence1 != null) {
             for (int i = 0; i < 128; i++) {
 
                 long address = writePosition.getVolatileValue(0);
@@ -721,7 +722,12 @@ public long lastSequenceNumber(@NotNull ExcerptContext ec, boolean approximate)
                     continue;
                 if (sequence == Sequence.NOT_FOUND)
                     break;
-                return sequence;
+                try {
+                    Wire wireForIndex = ec.wireForIndex();
+                    return wireForIndex == null ? sequence : linearScanByPosition(wireForIndex, Long.MAX_VALUE, sequence, address, true);
+                } catch (EOFException e) {
+                    throw new UncheckedIOException(e);
+                }
             }
         }
 

src/main/java/net/openhft/chronicle/queue/impl/single/SingleChronicleQueue.java

@@ -613,29 +613,29 @@ public int nextCycle(int cycle, @NotNull TailerDirection direction) throws Parse
      * which is updated last during append operation so may be possible that a single entry is available for reading
      * but not acknowledged by this method yet.
      *
-     * @see ExcerptTailer#approximateExcerptsInCycle(int)
+     * @see ExcerptTailer#excerptsInCycle(int)
      * @deprecated
      */
     @Deprecated(/* To be removed in x.25 */)
     public long approximateExcerptsInCycle(int cycle) {
         throwExceptionIfClosed();
         try (ExcerptTailer tailer = createTailer()) {
-            return tailer.approximateExcerptsInCycle(cycle);
+            return tailer.excerptsInCycle(cycle);
         }
     }
 
     /**
      * Returns an exact number of excerpts in a cycle available for reading. This may be a computationally
      * expensive operation.
      *
-     * @see ExcerptTailer#exactExcerptsInCycle(int)
+     * @see ExcerptTailer#excerptsInCycle(int)
      * @deprecated
      */
     @Deprecated(/* To be removed in x.25 */)
     public long exactExcerptsInCycle(int cycle) {
         throwExceptionIfClosed();
         try (ExcerptTailer tailer = createTailer()) {
-            return tailer.exactExcerptsInCycle(cycle);
+            return tailer.excerptsInCycle(cycle);
         }
     }
 

src/main/java/net/openhft/chronicle/queue/impl/single/SingleChronicleQueueStore.java

@@ -177,7 +177,7 @@ public String dump() {
     @NotNull
     @Override
     public String shortDump() {
-        return dump(WireType.BINARY_LIGHT,true);
+        return dump(WireType.BINARY_LIGHT, true);
     }
 
     @Override
@@ -315,20 +315,25 @@ public long sequenceForPosition(@NotNull final ExcerptContext ec, final long pos
         return indexing.sequenceForPosition(ec, position, inclusive);
     }
 
-    @Override
-    @Deprecated(/* To be removed in 5.25 */)
     public long lastSequenceNumber(@NotNull ExcerptContext ec) throws StreamCorruptedException {
-        return approximateLastSequenceNumber(ec);
+        throwExceptionIfClosedInSetter();
+        return indexing.lastSequenceNumber(ec);
     }
 
+    /**
+     * @deprecated Use {@link #lastSequenceNumber(ExcerptContext)} instead
+     */
+    @Deprecated(/* To be removed in x.26 */)
     public long approximateLastSequenceNumber(@NotNull ExcerptContext ec) throws StreamCorruptedException {
-        throwExceptionIfClosedInSetter();
-        return indexing.lastSequenceNumber(ec, true);
+        return lastSequenceNumber(ec);
     }
 
+    /**
+     * @deprecated Use {@link #lastSequenceNumber(ExcerptContext)} instead
+     */
+    @Deprecated(/* To be removed in x.26 */)
     public long exactLastSequenceNumber(@NotNull ExcerptContext ec) throws StreamCorruptedException {
-        throwExceptionIfClosedInSetter();
-        return indexing.lastSequenceNumber(ec, false);
+        return lastSequenceNumber(ec);
     }
 
     @NotNull

src/main/java/net/openhft/chronicle/queue/impl/single/StoreAppender.java

@@ -119,7 +119,7 @@ class StoreAppender extends AbstractCloseable
                         }
                     }
                     if (wire != null)
-                        resetPosition(false);
+                        resetPosition();
                 }
             } finally {
                 writeLock.unlock();
@@ -328,7 +328,7 @@ private void setCycle2(final int cycle, final WireStoreSupplier.CreateStrategy c
 
         wire.parent(this);
         wire.pauser(queue.pauserSupplier.get());
-        resetPosition(false);
+        resetPosition();
         queue.onRoll(cycle);
     }
 
@@ -358,7 +358,7 @@ private Wire createWire(@NotNull final WireType wireType) {
      * @return true if the header number is changed, otherwise false
      * @throws UnrecoverableTimeoutException todo
      */
-    private boolean resetPosition(boolean exact) {
+    private boolean resetPosition() {
         long originalHeaderNumber = wire.headerNumber();
         try {
             if (store == null || wire == null)
@@ -369,8 +369,7 @@ private boolean resetPosition(boolean exact) {
             Bytes<?> bytes = wire.bytes();
             assert !QueueSystemProperties.CHECK_INDEX || checkPositionOfHeader(bytes);
 
-            final long lastSequenceNumber = exact ? store.exactLastSequenceNumber(this)
-                    : store.approximateLastSequenceNumber(this);
+            final long lastSequenceNumber = store.lastSequenceNumber(this);
             wire.headerNumber(queue.rollCycle().toIndex(cycle, lastSequenceNumber + 1) - 1);
 
             assert !QueueSystemProperties.CHECK_INDEX || wire.headerNumber() != -1 || checkIndex(wire.headerNumber(), positionOfHeader);
@@ -437,7 +436,7 @@ private StoreAppender.StoreAppenderContext prepareAndReturnWriteContext(boolean
                     rollCycleTo(cycle);
 
                 long safeLength = queue.overlapSize();
-                resetPosition(false);
+                resetPosition();
                 assert !QueueSystemProperties.CHECK_INDEX || checkWritePositionHeaderNumber();
 
                 // sets the writeLimit based on the safeLength
@@ -657,7 +656,7 @@ protected void writeBytesInternal(final long index, @NotNull final BytesStore by
             rollCycleTo(cycle, this.cycle > cycle);
 
         // in case our cached headerNumber is incorrect.
-        resetPosition(true);
+        resetPosition();
 
         long headerNumber = wire.headerNumber();
 

src/main/java/net/openhft/chronicle/queue/impl/single/StoreTailer.java

@@ -1003,7 +1003,8 @@ public ExcerptTailer originalToEnd() {
                 break;
 
             case FOUND:
-                LoopForward: while (originalToEndLoopCondition(approximateLastIndex, index)) {
+                LoopForward:
+                while (originalToEndLoopCondition(approximateLastIndex, index)) {
                     final ScanResult result = moveToIndexResult(++index);
                     switch (result) {
                         case NOT_REACHED:
@@ -1124,7 +1125,7 @@ private void windBackCycle(int cycle) {
     }
 
     private boolean tryWindBack(final int cycle) {
-        final long count = exactExcerptsInCycle(cycle);
+        final long count = excerptsInCycle(cycle);
         if (count <= 0)
             return false;
         final RollCycle rollCycle = queue.rollCycle();
@@ -1212,22 +1213,10 @@ public boolean readAfterReplicaAcknowledged() {
     }
 
     @Override
-    public long approximateExcerptsInCycle(int cycle) {
+    public long excerptsInCycle(int cycle) {
         throwExceptionIfClosed();
         try {
-            return moveToCycle(cycle) ? store.approximateLastSequenceNumber(this) + 1 : -1;
-        } catch (StreamCorruptedException e) {
-            throw new IllegalStateException(e);
-        } finally {
-            releaseStore();
-        }
-    }
-
-    @Override
-    public long exactExcerptsInCycle(int cycle) {
-        throwExceptionIfClosed();
-        try {
-            return moveToCycle(cycle) ? store.exactLastSequenceNumber(this) + 1 : -1;
+            return moveToCycle(cycle) ? store.lastSequenceNumber(this) + 1 : -1;
         } catch (StreamCorruptedException e) {
             throw new IllegalStateException(e);
         } finally {
@@ -1249,7 +1238,7 @@ public TailerState state() {
      *              Must not be null.
      * @param index The index to read the history message in the {@code queue}.
      * @return This ExcerptTailer instance.
-     * @throws IORuntimeException if the provided {@code queue} couldn't be wound to the last index.
+     * @throws IORuntimeException   if the provided {@code queue} couldn't be wound to the last index.
      * @throws NullPointerException if the provided {@code queue} is null.
      */
     @NotNull