using agentE2E sink, with a node tailing a file, even with no activity i see ACKs over and over again, is this normal ?

The sink is:  collector(10000) { attr2hbase("apache_logs","f1","","ss_") }

2011-10-18 17:02:42,937 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: Starting checksum group called 20111018-170233074-0400.158065883163017.00000020
2011-10-18 17:02:42,937 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: initial checksum is 13318d7c272
2011-10-18 17:02:42,937 WARN com.cloudera.flume.core.Event: Tag node not found
2011-10-18 17:02:42,937 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: Finishing checksum group called '20111018-170233074-0400.158065883163017.00000020'
2011-10-18 17:02:42,937 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: Checksum succeeded 13318d7c272
2011-10-18 17:02:42,937 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: moved from partial to complete 20111018-170233074-0400.158065883163017.00000020



2011-10-18 17:02:52,943 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: Starting checksum group called 20111018-170243079-0400.158075888528921.00000020
2011-10-18 17:02:52,943 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: initial checksum is 13318d7e989
2011-10-18 17:02:52,943 WARN com.cloudera.flume.core.Event: Tag node not found
2011-10-18 17:02:52,943 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: Finishing checksum group called '20111018-170243079-0400.158075888528921.00000020'
2011-10-18 17:02:52,943 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: Checksum succeeded 13318d7e989
2011-10-18 17:02:52,943 INFO com.cloudera.flume.handlers.endtoend.AckChecksumChecker: moved from partial to complete 20111018-170243079-0400.158075888528921.00000020