Hi C* Devs,
I've got two questions relating to the CommitLogReader.
1.
I maintain the Cassandra port for FreeBSD. For C* 3.11.5 (OpenJDK
1.8.0_222, FreeBSD 12.1-RELEASE-p1 GENERIC amd64), there are currently test
failures in org.apache.cassandra.db.commitlog.CommitLogReaderTest with zero
mutations read in each case. Only testReadCount passes and it looks like
that's because the number of generated samples in the test is smaller than
the others. Increase the sample size to around 300 and it will fail too;
similarly, the others pass with a smaller sample size.
The tests are failing because CommitLogDescriptor#readHeader returns null,
a result of the checksum check failing: the checksum read from the file
(CommitLogDescriptor:175) is zero. Similarly version, id, and
parameterLength are all zero and from what I can tell the commit log in
these instances is just all zeros.
Any idea why a "large" number of mutations could cause a problem with the
commit log? Has this been seen and fixed on any of the officially supported
platforms (Linux, Darwin)?
2.
Because of #1 above, I started playing around with CommitLogReaderTest on
Linux (OpenJDK 1.8.0_232, Ubuntu 18.04). Checked out the 3.11.5 release
commit and changed just samples and readCount in
CommitLogReaderTest#testReadFromMidpoint as follows:
public void testReadFromMidpoint() throws Throwable
{
int samples = 100; // formerly 1000
int readCount = 60; // formerly 500
Shouldn't this fail uniformly every time with "Expected 60 seen mutations,
got: 50"? It produces somewhat random results:
[junit-timeout] Testcase:
testReadFromMidpoint(org.apache.cassandra.db.commitlog.CommitLogReaderTest):
FAILED
[junit-timeout] Expected 60 seen mutations, got: 55 expected:<60> but
was:<55>
[junit-timeout] junit.framework.AssertionFailedError: Expected 60 seen
mutations, got: 55 expected:<60> but was:<55>
[junit-timeout] at
org.apache.cassandra.db.commitlog.CommitLogReaderTest.testReadFromMidpoint(CommitLogReaderTest.java:111)
[junit-timeout] Testcase:
testReadFromMidpoint(org.apache.cassandra.db.commitlog.CommitLogReaderTest):
FAILED
[junit-timeout] Expected 60 seen mutations, got: 57 expected:<60> but
was:<57>
[junit-timeout] junit.framework.AssertionFailedError: Expected 60 seen
mutations, got: 57 expected:<60> but was:<57>
[junit-timeout] at
org.apache.cassandra.db.commitlog.CommitLogReaderTest.testReadFromMidpoint(CommitLogReaderTest.java:111)
Including, occasionally, the anticipated answer :)
[junit-timeout] Testcase:
testReadFromMidpoint(org.apache.cassandra.db.commitlog.CommitLogReaderTest):
FAILED
[junit-timeout] Expected 60 seen mutations, got: 50 expected:<60> but
was:<50>
[junit-timeout] junit.framework.AssertionFailedError: Expected 60 seen
mutations, got: 50 expected:<60> but was:<50>
[junit-timeout] at
org.apache.cassandra.db.commitlog.CommitLogReaderTest.testReadFromMidpoint(CommitLogReaderTest.java:111)
Shall I open a bug in JIRA for this or have I misunderstood how
testReadFromMidpoint works?
Thanks,
Angelo Polo
