Better detection of multiple log versions

neo4j · Sep 4, 2017 · 0142842 · 0142842
1 parent b272746
commit 0142842
Show file tree

Hide file tree

Showing 2 changed files with 32 additions and 2 deletions.
diff --git a/.../main/java/org/neo4j/kernel/impl/transaction/log/ReversedSingleFileTransactionCursor.java b/.../main/java/org/neo4j/kernel/impl/transaction/log/ReversedSingleFileTransactionCursor.java
@@ -74,6 +74,7 @@ private long[] sketchOutTransactionStartOffsets() throws IOException
         long[] offsets = new long[10_000];
         int offsetCursor = 0;
 
+        long logVersion = channel.getVersion();
         long startOffset = channel.position();
         while ( transactionCursor.next() )
         {
@@ -82,11 +83,15 @@ private long[] sketchOutTransactionStartOffsets() throws IOException
                 offsets = Arrays.copyOf( offsets, offsetCursor * 2 );
             }
             offsets[offsetCursor++] = startOffset;
-            long nextStartOffset = channel.position();
-            assert nextStartOffset > startOffset : "It looks like this channel moved over to another version";
             startOffset = channel.position();
         }
 
+        if ( channel.getVersion() != logVersion )
+        {
+            throw new IllegalArgumentException( "The channel which was passed in bridged multiple log versions, it started at version " +
+                    logVersion + ", but continued through to version " + channel.getVersion() + ". This isn't supported" );
+        }
+
         offsetsLength = offsetCursor;
         chunkStartOffsetIndex = offsetCursor;
         totalSize = channel.position();

diff --git a/...t/java/org/neo4j/kernel/impl/transaction/log/ReversedSingleFileTransactionCursorTest.java b/...t/java/org/neo4j/kernel/impl/transaction/log/ReversedSingleFileTransactionCursorTest.java
@@ -41,7 +41,11 @@
 import org.neo4j.test.rule.TestDirectory;
 import org.neo4j.test.rule.fs.DefaultFileSystemRule;
 
+import static org.hamcrest.CoreMatchers.containsString;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.fail;
+
 import static org.neo4j.io.ByteUnit.mebiBytes;
 import static org.neo4j.kernel.impl.store.record.Record.NO_LABELS_FIELD;
 import static org.neo4j.kernel.impl.transaction.log.GivenTransactionCursor.exhaust;
@@ -121,6 +125,27 @@ public void shouldHandleEmptyLog() throws Exception
         assertEquals( 0, readTransactions.length );
     }
 
+    @Test
+    public void shouldDetectAndPreventChannelReadingMultipleLogVersions() throws Exception
+    {
+        // given
+        writeTransactions( 1, 1, 1 );
+        logFile.rotate();
+        writeTransactions( 1, 1, 1 );
+
+        // when
+        try ( ReadAheadLogChannel channel = (ReadAheadLogChannel) logFile.getReader( start( 0 ) ) )
+        {
+            new ReversedSingleFileTransactionCursor( channel, new VersionAwareLogEntryReader<>() );
+            fail( "Should've failed" );
+        }
+        catch ( IllegalArgumentException e )
+        {
+            // then good
+            assertThat( e.getMessage(), containsString( "multiple log versions" ) );
+        }
+    }
+
     private CommittedTransactionRepresentation[] readAllFromReversedCursor() throws IOException
     {
         try ( ReversedSingleFileTransactionCursor cursor = txCursor() )