[jira] [Created] (CASSANDRA-11288) Schema agreement appears to be false positive following a DROP TABLE command

["Oliver Lockwood (JIRA)" <ji...@apache.org>]

Oliver Lockwood created CASSANDRA-11288:
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             Summary: Schema agreement appears to be false positive following a DROP TABLE command
                 Key: CASSANDRA-11288
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11288
             Project: Cassandra
          Issue Type: Bug
         Environment: Cassandra 2.0.14.439 (DSE 4.6.7)
2 nodes
Connecting with Datastax Java driver 2.1.8
            Reporter: Oliver Lockwood
            Priority: Minor


As part of a schema migration operation, our application is calling the following operations on the Java driver consecutively:
{{session.execute("DROP TABLE table_name");
session.execute("CREATE TABLE table_name (...)");}}

The second of these sometimes fails with a {{DriverException}} whose message is "Table keyspace.table_name already exists".

In the schema migration operation, there's 4 of these drop/create pairings and, although it's random which exact one fails, we've never managed to get further than the third operation in approximately 10 attempts - so there's a reasonably high proportion of failure.

I don't believe this is a driver issue because the driver is checking for schema agreement (as per https://github.com/datastax/java-driver/blob/2.1/driver-core/src/main/java/com/datastax/driver/core/ControlConnection.java#L701) and we are seeing a log message to that effect.
{{c.d.d.c.ControlConnection - [] [] [] [] [] [] [] [] Checking for schema agreement: versions are [02bce936-fddd-3bef-bb54-124d31bede57]}}.
(This log message appears in between our own logs which say "Executing statement DROP TABLE..." and "Executing statement CREATE TABLE...", so we can be reasonably sure this log message refers to the DROP operation being viewed as "in agreement".

Could this be a bug in the Cassandra server erroneously reporting that the schemas are in agreement across the 2 nodes when, in fact, they are not?



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