Known limitation that a read only queue assumes the roll cycle won't …

…change and is set correctly (#1645)

* Known limitation that a read only queue assumes the roll cycle won't change and is set correctly

* Known limitation that a read only queue assumes the roll cycle won't change and is set correctly

README.adoc

@@ -207,6 +207,11 @@ Non-batching streaming components are highly performant, deterministic, and repr
 You can reproduce bugs which only show up after a million events played in a particular order, with accelerated realistic timings.
 This makes using Stream processing attractive for systems which need a high degree of quality outcomes.
 
+==== Setting the Roll Cycle of a queue
+
+You can have different instances of `SingleChronicleQueue` set with different roll cycles.
+However, if you have instances of `SingleChronicleQueue` with the same path but different roll cycles, first queue to be created determines the roll cycle, even if the first queue only have a tailer. If the first queue is read-only, it will fail to read the queue if the roll cycle is later different.
+
 == Downloading Chronicle Queue
 
 Releases are available on Maven Central as:

src/test/java/net/openhft/chronicle/queue/issue/ChangeRollCycleTest.java

@@ -0,0 +1,105 @@
+package net.openhft.chronicle.queue.issue;
+
+import net.openhft.chronicle.core.OS;
+import net.openhft.chronicle.core.io.IOTools;
+import net.openhft.chronicle.queue.ChronicleQueue;
+import net.openhft.chronicle.queue.ExcerptAppender;
+import net.openhft.chronicle.queue.ExcerptTailer;
+import net.openhft.chronicle.queue.RollCycles;
+import net.openhft.chronicle.wire.DocumentContext;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assume.assumeFalse;
+
+/**
+ * Test class to verify the behavior of Chronicle Queue when changing Roll Cycles.
+ * It checks the compatibility and visibility of data written with one Roll Cycle
+ * and accessed with another.
+ */
+public class ChangeRollCycleTest {
+
+    @Test
+    public void changeRollCycleWithReadOnlyTailer() {
+        testChangeRollCycle(true);
+    }
+
+    @Test
+    public void changeRollCycleWithReadWriteTailer() {
+        testChangeRollCycle(false);
+    }
+
+    /**
+     * Test the behavior of Chronicle Queue when switching between roll cycles.
+     *
+     * @param readOnly whether the tailer should be in read-only mode
+     */
+    private void testChangeRollCycle(boolean readOnly) {
+        // Define the queue path
+        String queuePath = OS.getTarget() + "/changeRollCycle-" + System.nanoTime();
+
+
+        // Step 1: Open a queue with a FAST_DAILY roll cycle and a tailer
+        try (ChronicleQueue q1 = ChronicleQueue.singleBuilder(queuePath)
+                .rollCycle(RollCycles.FAST_DAILY)
+                .readOnly(readOnly)
+                .build();
+             ExcerptTailer tailer = q1.createTailer()) {
+
+            // Verify the queue is initially empty
+            try (DocumentContext dc = tailer.readingDocument()) {
+                assertFalse("Queue should be empty initially", dc.isPresent());
+            }
+
+            // Step 2: Reopen the queue with a WEEKLY roll cycle and write data
+            try (ChronicleQueue q2 = ChronicleQueue.singleBuilder(queuePath)
+                    .rollCycle(RollCycles.WEEKLY)
+                    .build();
+                 ExcerptAppender appender2 = q2.createAppender()) {
+
+                // Write a messages to the queue
+                appender2.writeText("Hello");
+
+                // Step 3: Reopen the queue with a WEEKLY roll cycle and write data
+                try (ChronicleQueue q3 = ChronicleQueue.singleBuilder(queuePath)
+                        .rollCycle(RollCycles.FAST_HOURLY)
+                        .build();
+                     ExcerptAppender appender3 = q3.createAppender()) {
+                    assertEquals(q2.rollCycle(), q3.rollCycle());
+
+                    // Write two messages to the queue
+                    appender3.writeText("World");
+
+                    if (readOnly)
+                           assertEquals("Roll cycle should match WEEKLY for read-only mode",
+RollCycles.WEEKLY, q3.rollCycle());
+                }
+
+                // If the tailer is read-only, the roll cycle cannot not be changed
+                // The read only case assumes there queue is historical and the roll cycle is fixed
+                assumeFalse(readOnly);
+
+                // Step 4: Verify the data can be read back correctly
+                assertEquals("First message should match", "Hello", tailer.readText());
+
+                if (readOnly)
+                    assertEquals("Roll cycle should match WEEKLY for read-only mode",
+                                RollCycles.WEEKLY,
+                                q1.rollCycle());
+
+                assertEquals("Second message should match", "World", tailer.readText());
+
+                assertEquals(q2.rollCycle(), q1.rollCycle());
+
+                // Verify there is no extra data in the queue
+                try (DocumentContext dc = tailer.readingDocument()) {
+                    assertFalse("No more data should be present in the queue", dc.isPresent());
+                }
+            }
+        } finally {
+            // Clean up the queue directory to avoid leaving test artifacts
+            IOTools.deleteDirWithFiles(queuePath, 2);
+        }
+    }
+}