37 lines
1.3 KiB
Markdown
37 lines
1.3 KiB
Markdown
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# priorityq - generic priority queue in Go
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This module was inspired by [a reddit post][reddit] wherein /u/zandery23 asked
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how to implement a priority queue in Go. A fantastic solution was [provided by
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/u/Ploobers][sol]. That's probably right for 99 out of 100 use cases, but it's
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not completely precise.
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Particularly, the second select block does not guarantee that an item from the
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priority queue will be taken if there is also an item in the regular queue.
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```go
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select {
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case job := <-mq.priorityQueue:
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// ...
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case job := <-mq.regularQueue:
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// ...
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// ...
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}
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```
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From the [Go Language Specification][go_select]:
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> If one or more of the communications can proceed, a single one that can
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> proceed is chosen via a uniform pseudo-random selection.
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Thus, it is possible for the second case to be chosen even if the first case is
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also ready.
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The `precise` package in this module implements a concurrent priority queue that
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guarantees receipt of a high-priority items before low-priority ones. This is
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primarily a fun exercise, I cannot recommend that anyone actually use this in a
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real project.
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[reddit]: https://www.reddit.com/r/golang/comments/11drc17/worker_pool_reading_from_two_channels_one_chan/
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[sol]: https://www.reddit.com/r/golang/comments/11drc17/worker_pool_reading_from_two_channels_one_chan/jabfvkh/
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[go_select]: https://go.dev/ref/spec#Select_statements
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