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< a href = "index" > Index< / a >
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< h1 > < a id = "user-content-reload-config" class = "anchor" aria-hidden = "true" href = "#reload-config" > < span aria-hidden = "true" class = "octicon octicon-link" > < / span > < / a > Reload config< / h1 >
< p > This serves as design draft of reload config system< / p >
< div class = "highlight highlight-source-wsd" > < pre > < span class = "pl-k" > @startuml< / span > Reload config
< span class = "pl-k" > skinparam< / span > < span class = "pl-k" > defaultFontName< / span > < span class = "pl-s" > Iosevka Term SS08< / span >
< span class = "pl-k" > participant< / span > < span class = "pl-c1" > admin< / span >
< span class = "pl-k" > participant< / span > < span class = "pl-c1" > other_service< / span >
< span class = "pl-k" > participant< / span > < span class = "pl-c1" > config_service< / span >
< span class = "pl-k" > participant< / span > < span class = "pl-c1" > storage< / span >
< span class = "pl-k" > ==< / span > < span class = "pl-s" > Admin handle< / span > < span class = "pl-k" > ==< / span >
< span class = "pl-c1" > admin< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > config_service< / span > : set/update/delete config
< span class = "pl-c1" > config_service< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > storage< / span > : set/update/delete config
< span class = "pl-k" > ==< / span > < span class = "pl-s" > Other service handle< / span > < span class = "pl-k" > ==< / span >
< span class = "pl-c1" > other_service< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > other_service< / span > : init service
< span class = "pl-k" > activate< / span > < span class = "pl-c1" > other_service< / span >
< span class = "pl-c1" > other_service< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > storage< / span > : make connection
< span class = "pl-k" > loop< / span >
< span class = "pl-c1" > other_service< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > storage< / span > : listen on config change
< span class = "pl-c1" > other_service< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > other_service< / span > : save config to memory
< span class = "pl-k" > end< / span >
< span class = "pl-k" > deactivate< / span > < span class = "pl-c1" > other_service< / span >
< span class = "pl-c1" > other_service< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > other_service< / span > : do business
< span class = "pl-k" > activate< / span > < span class = "pl-c1" > other_service< / span >
< span class = "pl-c1" > other_service< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > other_service< / span > : get config
< span class = "pl-c1" > other_service< / span > < span class = "pl-k" > -> < / span > < span class = "pl-c1" > other_service< / span > : do other business
< span class = "pl-k" > deactivate< / span > < span class = "pl-c1" > other_service< / span >
< span class = "pl-k" > @enduml< / span > < / pre > < / div >
< p > Config storage can be any key value storage or database like etcd, Consul, mySQL, ...< / p >
< p > If storage is key value storage, maybe there is API to listen on config change.
Otherwise we should create a loop to get all config from storage for some interval, for example each 5 minute.< / p >
< p > Each < code > other_service< / code > need to get config from its memory, not hit < code > storage< / code > .
So there is some delay between upstream config (config in < code > storage< / code > ) and downstream config (config in < code > other_service< / code > ), but maybe we can forgive that delay (???).< / p >
< p > Pros:< / p >
< ul >
< li >
< p > Config can be dynamic, service does not need to restart to apply new config.< / p >
< / li >
< li >
< p > Each service only keep 1 connection to < code > storage< / code > to listen to config change, not hit < code > storage< / code > for each request.< / p >
< / li >
< / ul >
< p > Cons:< / p >
< ul >
< li > Each service has 1 more dependency, aka < code > storage< / code > .< / li >
< li > Need to handle fallback config, incase < code > storage< / code > failure.< / li >
< li > Delay between upstream/downstream config< / li >
< / ul >
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Feel free to ask me via
< a href = "mailto:hauvipapro+posts@gmail.com" > email< / a > or
< a rel = "me" href = "https://hachyderm.io/@haunguyen" > Mastodon< / a >
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