Master save and load state from etcd, and register on etcd. #2539
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helinwang
requested review from
Yancey0623,
dzhwinter,
gongweibao,
jacquesqiao,
typhoonzero and
wangkuiyi
go/master/service.go
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Add logs to inform recover event.
go/cmd/master/master.go
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inMemStore have not much code, but it'll be still more clear if we put it to inmen_store.go corresponding to etcd_store.go, also the interface Store.
go/master/etcd_store.go
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I really don't know when to do cli.Close() to release etcd client resources, shall we catch signal INT and then call a DeleteEtcdStore? Or we can leave this to OS in this version.
I've also created an issue to talk about "how to gracefully shutdown master and pservers"
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Thanks! Very good point. Added TODO in the source code as well.
go/cmd/master/master.go
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Is inMemStore for test only?
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I see, if endpoints is "", master will use inMemStore and have no fault tolerance.
go/cmd/master/master.go
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just a question, why here do not use code of
store, err := master.NewEtcdStore(eps, master.DefaultLockPath, master.DefaultStatePath, *ttlSec)There was a problem hiding this comment.
@dzhwinter great question!
If we use store, err := ... here, it would be incorrect. Because then we actually created a new store variable, because we are in a new scope. The store would be a different variable than var store master.Store. What happened here is called store is "shadowed".
Please see here for me detail.
https://developmentality.wordpress.com/2014/03/03/go-gotcha-1-variable-shadowing-within-inner-scope-due-to-use-of-operator/
go vet -shadow can detect them:
https://golang.org/cmd/vet/#hdr-Shadowed_variables
:= is called short variable declarations
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so kind of you. get it, thanks!
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Fixes: #2537 #2506