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Cache async operations invoke future listeners on Striped pool threads:, which can cause deadlocks and/or reduce cache performance.

IgniteFuture fut = cache.putAsync(1, 1);
fut.listen(f -> {
    // Executes on Striped pool and deadlocks.
    cache.replace(1, 2);
});

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Those users can force the old behavior with `IgniteConfiguration.setAsyncContinuationExecutor(Runnable::run)`.

Performance

Executing continuation on a different thread involves some overhead. Local benchmark with integer key and value shows ~6% drop (see JmhCacheAsyncListenBenchmark in the PoC).

In a real world workload the difference should be insignificant.

Benchmark                          Mode  Cnt      Score      Error  Units
JmhCacheAsyncListenBenchmark.put  thrpt   10  77859.584 ± 2071.196  ops/s (before)
JmhCacheAsyncListenBenchmark.put  thrpt   10  73393.986 ± 1336.420  ops/s (after)

Discussion Links

IEP thread: http://apache-ignite-developers.2346864.n4.nabble.com/IEP-70-Async-Continuation-Executor-td51775.html

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