Benedict Elliott Smith created CASSANDRA-21662:
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Summary: Accord executor QoS and incremental execution
Key: CASSANDRA-21662
URL: https://issues.apache.org/jira/browse/CASSANDRA-21662
Project: Apache Cassandra
Issue Type: Bug
Components: Accord
Reporter: Benedict Elliott Smith
Accord executor QoS and incremental execution
QoS: Tasks are categorised so that their relative arrival/service rate can be
tracked by
7-bit decaying counters. Work may be assigned by a mixture of highest
priority task or
least-serviced queue by a deficit round-robin scheme. This prevents e.g.
cache flushes
from dominating executor threads.
Incremental Execution: Implementation fully implements enriched ASYNC/INCR
ExecutionContext
semantics, so that tasks may be decomposed into multiple steps with optional
ATOMIC isolation.
This permits sync points in particular to be processed in smaller batches,
allowing smaller
non-conflicting tasks to interleave.
Also Improve:
* Continuation tasks allow declaring work that logically continues prior work,
and that must
execute before treating the initiating task as complete (distinct from
notifying any callback);
Continuation or partial incremental tasks that fail with ATOMIC visibility
mark a key as unavailable
to prevent reading inconsistent state.
* Consequences of tasks are submitted as part of the task's completion
* Consequences of durable tasks that fail are cancelled before they are
submitted
* Handle partial task failure: propagate failure to counting results instead
of silently
decrementing, and abandon dependent continuations.
* ExclusiveExecutor releases its lock eagerly, opening up
tryExecuteImmediately to more executions
* Memtables blocking an Accord durability status update will be flushed
periodically
* NoSpamLogger.NoDuplicateSpamLogStatement: rate-limit per distinct exception
* Claude-generated formal specification of execution semantics under
formalise/accord/execution
* AutoRepair shutdown executors simultaneously, and terminate running sessions
* Shutdown UDF and SASI executors
* FailureDetector: pass Double.MAX_VALUE on forceConvict to ensure listeners
process an explicit shutdown
Also Fix:
* Data races updating Task.info (between executing thread and executor lock
owner)
* AccordExecutor/ThreadLocalTaskRunner lock accounting could be corrupted on
shutdown
* SignalLock incorrectly limited signals to MAX_THREADS not MAX_SIGNAL_COUNT
(throwing an exception)
* SignalLock invisible bug in tryAcquireAsyncInAwaitLoop
* Reject negative histogram values (LogLinearHistogram,
LogLinearDecayingHistograms), and ensure callers do not submit
* RepairOption.permitNoQuorum() returned repairAccord instead of
permitNoQuorum.
* FailureDetector: do not convict endpoints already marked down, since Accord
may become active while marked !isAlive;
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