Jaydeepkumar Chovatia created CASSANDRA-18758:
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Summary: Detect token-ownership mismatch
Key: CASSANDRA-18758
URL: https://issues.apache.org/jira/browse/CASSANDRA-18758
Project: Cassandra
Issue Type: Improvement
Components: Cluster/Gossip
Reporter: Jaydeepkumar Chovatia
Assignee: Jaydeepkumar Chovatia
*Problem Statement*
As we know, Cassandra exchanges important topology and token-ownership-related
details over Gossip. Cassandra internally maintains the following two separate
caches that have the token-ownership information maintained: 1) Gossip cache
and 2) Storage Service cache. The first Gossip cache is updated on a node,
followed by the storage service cache. In the hot path, ownership is calculated
from the storage service cache. Since two separate caches are maintaining the
same information, then inconsistencies are bound to happen. It could be very
well feasible that the Gossip cache has up-to-date ownership of the Cassandra
cluster, but the service cache does not, and in that scenario, inconsistent
data will be served to the user.
Currently, there is no mechanism in Cassandra that detects and fixes these two
caches.
*Long-term solution*
We are going with the long-term transactional metadata
(https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-21) to handle such
inconsistencies, and that’s the right thing to do.
*Short-term solution*
But CEP-21 might take some time, and until then, there is a need to detect such
inconsistencies. Once we detect inconsistencies, then we could have two
options: 1) Simply restart the node or 2) Fix the inconsistencies on-the-fly.
This JIRA is providing a short-term solution.
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