mirror of
https://github.com/scylladb/scylladb.git
synced 2026-04-23 18:10:39 +00:00
49ee9d9785
Consider the following scenario:
1. Let nodes A,B,C form a cluster with RF=3
2. Write query with CL=QUORUM is submitted and is acknowledged by
nodes B,C
3. Follow-up read query with CL=QUORUM is sent to verify the write
from the previous step
4. Coordinator sends data/digest requests to the nodes A,B. Since the
node A is missing data, digest mismatches and data reconciliation
is triggered
5. The node A or B fails, becomes unavailable, etc
6. During reconciliation, data requests are sent to node A,B and fail
failing the entire read query
When the above scenario happens, the tests using `start_writes()` fail
with the following stacktrace:
```
...
> await finish_writes()
test/cluster/test_tablets_migration.py:259:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
test/pylib/util.py:241: in finish
await asyncio.gather(*tasks)
test/pylib/util.py:227: in do_writes
raise e
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
worker_id = 1
...
> rows = await cql.run_async(rd_stmt, [pk])
E cassandra.ReadFailure: Error from server: code=1300 [Replica(s) failed to execute read] message="Operation failed for test_1767777001181_bmsvk.test - received 1 responses and 1 failures from 2 CL=QUORUM." info={'consistency': 'QUORUM', 'required_responses': 2, 'received_responses': 1, 'failures': 1}
```
Note that when a node failure happens before/during a read query,
there is no test failure as the speculative retries are enabled
by default. Hence an additional data/digest read is sent to the third
remaining node.
However, the same speculative read is cancelled the moment, the read
query reaches CL which may trigger a read-repair.
This change:
- Retries the verification read in start_writes() on failure to mitigate
races between reads and node failures
- Adds additional logging to correlate Python exceptions with Scylla logs
Fixes https://github.com/scylladb/scylladb/issues/27478
Fixes https://github.com/scylladb/scylladb/issues/27974
Fixes https://github.com/scylladb/scylladb/issues/27494
Fixes https://github.com/scylladb/scylladb/issues/23529
Note that this change test flakiness observed during tablet transitions.
However, it serves as a workaround for a higher-level issue
https://github.com/scylladb/scylladb/issues/28125
Closes scylladb/scylladb#28140
(cherry picked from commit e07fe2536e)
Closes scylladb/scylladb#28825