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POasync reply in registry pattern
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copied!<p>I'm learning go, and I would like to explore some patterns.</p> <p>I would like to build a Registry component which maintains a map of some stuff, and I want to provide a serialized access to it:</p> <p>Currently I ended up with something like this:</p> <pre><code>type JobRegistry struct { submission chan JobRegistrySubmitRequest listing chan JobRegistryListRequest } type JobRegistrySubmitRequest struct { request JobSubmissionRequest response chan Job } type JobRegistryListRequest struct { response chan []Job } func NewJobRegistry() (this *JobRegistry) { this = &JobRegistry{make(chan JobRegistrySubmitRequest, 10), make(chan JobRegistryListRequest, 10)} go func() { jobMap := make(map[string] Job) for { select { case sub := <- this.submission: job := MakeJob(sub.request) // .... jobMap[job.Id] = job sub.response <- job.Id case list := <- this.listing: res := make([]Job, 0, 100) for _, v := range jobMap { res = append(res, v) } list.response <- res } /// case somechannel.... } }() return } </code></pre> <p>Basically, I encapsulate each operation inside a struct, which carries the parameters and a response channel.</p> <p>Then I created helper methods for end users:</p> <pre><code>func (this *JobRegistry) List() ([]Job, os.Error) { res := make(chan []Job, 1) req := JobRegistryListRequest{res} this.listing <- req return <-res, nil // todo: handle errors like timeouts } </code></pre> <p>I decided to use a channel for each type of request in order to be type safe.</p> <hr> <p>The problem I see with this approach are:</p> <ul> <li><p>A lot of boilerplate code and a lot of places to modify when some param/return type changes</p></li> <li><p>Have to do weird things like create yet another wrapper struct in order to return errors from within the handler goroutine. (If I understood correctly there are no tuples, and no way to send multiple values in a channel, like multi-valued returns)</p></li> </ul> <p>So, I'm wondering whether all this makes sense, or rather just get back to good old locks.</p> <p>I'm sure that somebody will find some clever way out using channels.</p>

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