Just happened again, seems to be with the same column family (at least on a flusher thread for which the last activity was flushing a memtable for that CF).
It also looks like MemtablePostFlusher tasks blocked (and not getting cleared) as evidenced by tpstats: Pool Name Active Pending Completed Blocked All time blocked MemtablePostFlusher 1 18 16 0 0 Dan From: Dan Hendry [mailto:dan.hendry.j...@gmail.com] Sent: November-10-11 14:49 To: 'user@cassandra.apache.org' Subject: 1.0.2 Assertion Error Just saw this weird assertion after upgrading one of my nodes from 0.8.6 to 1.0.2 (its been running fine for a few hours now): INFO [FlushWriter:9] 2011-11-10 13:08:58,882 Memtable.java (line 237) Writing Memtable-Data@1388955390(25676955/430716097 serialized/live bytes, 478913 ops) ERROR [FlushWriter:9] 2011-11-10 13:08:59,513 AbstractCassandraDaemon.java (line 133) Fatal exception in thread Thread[FlushWriter:9,5,main] java.lang.AssertionError: CF size changed during serialization: was 4 initially but 3 written at org.apache.cassandra.db.ColumnFamilySerializer.serializeForSSTable(ColumnFam ilySerializer.java:94) at org.apache.cassandra.db.ColumnFamilySerializer.serializeWithIndexes(ColumnFa milySerializer.java:112) at org.apache.cassandra.io.sstable.SSTableWriter.append(SSTableWriter.java:177) at org.apache.cassandra.db.Memtable.writeSortedContents(Memtable.java:264) at org.apache.cassandra.db.Memtable.access$400(Memtable.java:47) at org.apache.cassandra.db.Memtable$4.runMayThrow(Memtable.java:289) at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:30) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.ja va:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:9 08) at java.lang.Thread.run(Thread.java:662) After taking a quick peek at the code, it looks like the numbers ("4 initially but 3 written") refer to the number of columns (in the memtable?). Given the byte size of the memtable being flushed, there are *certainly* more than 4 columns. Besides this error, there are no other unexpected or unusual log entries and the node seems to be behaving normally. Thoughts? Dan Hendry
