| 摘要 |
In a stream computing application, data may be transmitted between operators using tuples. However, the receiving operator may not evaluate these tuples as they arrive but instead wait to evaluate a group of tuples-i.e., a window. A window is typically triggered when a buffer associated with the receiving operator reaches a maximum window size or when a predetermined time period has expired. Additionally, a window may be triggered by a monitoring a tuple rate-i.e., the rate at which the operator receives the tuples. If the tuple rate exceeds or falls below a threshold, a window may be triggered. Further, the number of exceptions, or the rate at which an operator throws exceptions, may be monitored. If either of these parameters satisfies a threshold, a window may be triggered, thereby instructing an operator to evaluate the tuples contained within the window.
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