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59 lines
2.0 KiB
Markdown
59 lines
2.0 KiB
Markdown
---
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outline: deep
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---
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# Generating `khatru` relays dynamically and serving them from the same path
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Suppose you want to expose a different relay interface depending on the subdomain that is accessed. I don't know, maybe you want to serve just events with pictures on `pictures.example.com` and just events with audio files on `audios.example.com`; maybe you want just events in English on `en.example.com` and just examples in Portuguese on `pt.example.com`, there are many possibilities.
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You could achieve that with a scheme like the following
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```go
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var topLevelHost = "example.com"
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var mainRelay = khatru.NewRelay() // we're omitting all the configuration steps for brevity
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var subRelays = xsync.NewMapOf[string, *khatru.Relay]()
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func main () {
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handler := http.HandlerFunc(dynamicRelayHandler)
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log.Printf("listening at http://0.0.0.0:8080")
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http.ListenAndServe("0.0.0.0:8080", handler)
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}
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func dynamicRelayHandler(w http.ResponseWriter, r *http.Request) {
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var relay *khatru.Relay
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subdomain := r.Host[0 : len(topLevelHost)-len(topLevelHost)]
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if subdomain == "" {
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// no subdomain, use the main top-level relay
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relay = mainRelay
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} else {
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// call on subdomain, so get a dynamic relay
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subdomain = subdomain[0 : len(subdomain)-1] // remove dangling "."
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// get a dynamic relay
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relay, _ = subRelays.LoadOrCompute(subdomain, func () *khatru.Relay {
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return makeNewRelay(subdomain)
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})
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}
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relay.ServeHTTP(w, r)
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}
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func makeNewRelay (subdomain string) *khatru.Relay {
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// somehow use the subdomain to generate a relay with specific configurations
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relay := khatru.NewRelay()
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switch subdomain {
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case "pictures":
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// relay configuration shenanigans go here
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case "audios":
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// relay configuration shenanigans go here
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case "en":
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// relay configuration shenanigans go here
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case "pt":
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// relay configuration shenanigans go here
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}
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return relay
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}
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```
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In practice you could come up with a way that allows all these dynamic relays to share a common underlying datastore, but this is out of the scope of this example.
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