A couple of comments. This is probably obvious, but I wanted to point out that matthe...'s code would require *all *access to the map to be synchronized using the mutex. It's a simple and effective solution. One downside to his code is that it holds the lock for the duration of the Copy(). This may be unacceptable depending on the size of the map and your latency requirements. If the map is very, very large, this could block a writer for an indeterminate amount of time.
If your map met the requirements for sync.Map <https://golang.org/pkg/sync/#Map>, that struct contains a Range() method that allows for concurrent access. Depending on the requirements for the temporal strictness of the "snapshot", you could then use that function to create a copy without blocking other goroutines which might be attempting to write to the map. There are other, more complicated way that the Copy() lock time could be made constant, but they are significantly complicated. On Friday, January 26, 2018 at 9:56:38 PM UTC-5, matthe...@gmail.com wrote: > > Why not this? > > type StructMap map[string]*SomeStruct > > type SyncStructMap struct { > *sync.Mutex // maybe change to *sync.RWMutex if there are mixed > read/write synced operations > StructMap > } > > func (a SyncStructMap) Copy() StructMap { > out := make(StructMap) > a.Lock() > for key, value := range a.StructMap { > out[key] = value > } > a.Unlock() > return out > } > > // call with go keyword to make it execute concurrently > func (a SyncStructMap) EncodeAndWrite() { > c := a.Copy() > // encode c then write to file > } > > Matt > > On Friday, January 26, 2018 at 4:02:09 PM UTC-6, Tamás Gulácsi wrote: >> >> Do those *SomeStruct change during map serialization, or only the map >> (new keys / delete keys)? >> If they do, you'll have to lock them too, not just the map access! >> >> -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
