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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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• Add IgniteConfiguration#asyncContinuationExecutor (of type Executor).
• Use ForkJoinPool#commonPool by default (when null / not set).
• Use this executor for all Cache and Compute async continuations

This automatically fixes the same issue in Java, .NET and C++ (thick), because thick integrations use direct JNI callbacks for Futures.

NOTE: This IEP is NOT related to scan query filters, cache entry processors, etc, which also run on Striped pool.

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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.

Discussion Links

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

Original discussions: 

• http://apache-ignite-users.70518.x6.nabble.com/Replace-or-Put-after-PutAsync-causes-Ignite-to-hang-td27871.html
• http://apache-ignite-developers.2346864.n4.nabble.com/Re-EXTERNAL-Re-Replace-or-Put-after-PutAsync-causes-Ignite-to-hang-td42921.html

Reference Links

PoC: https://github.com/apache/ignite/pull/8870

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