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In one ExecutionJobVertex, when a configurable percentage of executions has been finished, the speculative execution thread begin really work.
Long Running Time
All In speculative execution thread all executions' interval between the current time and it first create/deploying time before it failover in one ExecutionJobVertex are calculated. when the running time of a execution is greater than a configurable multiple of the median of the running time of other finished executions, this execution is defined as long tail execution.
Slow Processing Throughput
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The primary characteristic of long tail tasks is that their processing throughput are much slower than the expected or than other normal tasks.
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Scheduling of Speculative Executions
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