There is a need for sending tablet info to the drivers so they can be tablet aware. For the best performance we want to get this info lazily only when it is needed.
The info is send when driver asks about the information that the specific tablet contains and it is directed to the wrong node/shard so it could use that information for every subsequent query. If we send the query to the wrong node/shard, we want to send the RESULT message with additional information about the tablet (replicas and token range) in custom_payload.
Mechanism for sending custom_payload added.
Sending custom_payload tested using three node cluster and cqlsh queries. I used RF=1 so choosing wrong node was testable.
I also manually tested it with the python-driver and confirmed that the tablet info can be deserialized properly.
Automatic tests added.
Closesscylladb/scylladb#15410
* github.com:scylladb/scylladb:
docs: add documentation about sending tablet info to protocol extensions
Add tests for sending tablet info
cql3: send tablet if wrong node/shard is used during modification statement
cql3: send tablet if wrong node/shard is used during select statement
locator: add function to check locality
locator: add function to check if host is local
transport: add function to add tablet info to the result_message
transport: add support for setting custom payload
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