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Go: Compose MAC addresses sent by multiple devices (#59)
With this change you'll be able to send MAC addresses from multiple devices, because MAC addresses are accumulated in special asynchronous data structure: macs.SetTTL. macs.SetTTL will keep unique mac addresses and delete them after specified amount of time (TTL aka time to live). If long-season will receive more MAC addresses, macs.SetTTL will reset TTL of MAC address that occurred again during update process. TTL of single mac address can be configure with LS_SINGLE_ADDR_TTL environment variable. You can also modify mac addresses refresh time with LA_REFRESH_TIME environmental variable.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,3 @@ | ||
| // Package macs contains functions, procedures and data types | ||
| // for manipulating hardware addresses. | ||
| package macs |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,130 @@ | ||
| package macs | ||
|
|
||
| import ( | ||
| "context" | ||
| "net" | ||
| "time" | ||
| ) | ||
|
|
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| // SetTTL is set for mac addresses with special daemon running | ||
| // in the background that will delete given mac addresses after | ||
| // specified amount of time (TTL). | ||
| // | ||
| // SetTTL is completely thread safe. Probably. | ||
| type SetTTL struct { | ||
| m map[string]*time.Timer | ||
| toAdd chan setItem | ||
| toDel chan string | ||
| retrieveSignal chan struct{} | ||
| macSlice chan []net.HardwareAddr | ||
| } | ||
|
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| type setItem struct { | ||
| value string | ||
| ttl time.Duration | ||
| } | ||
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| // NewSetTTL returns initialised pointer to SetTTL. | ||
| func NewSetTTL(ctx context.Context) *SetTTL { | ||
| res := &SetTTL{ | ||
| m: map[string]*time.Timer{}, | ||
| toAdd: make(chan setItem), | ||
| toDel: make(chan string), | ||
| retrieveSignal: make(chan struct{}), | ||
| macSlice: make(chan []net.HardwareAddr), | ||
| } | ||
|
|
||
| // start daemon in new goroutine | ||
| go res.daemon(ctx) | ||
|
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| return res | ||
| } | ||
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| // Push adds given HardwareAddr to set and setup its TTL. | ||
| // If given HardwareAddr is already in the set, it's reset | ||
| // its TTL to given amount of time duration. | ||
| func (s *SetTTL) Push(addr net.HardwareAddr, ttl time.Duration) { | ||
| s.toAdd <- setItem{ | ||
| value: string(addr), | ||
| ttl: ttl, | ||
| } | ||
| } | ||
|
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| // Slice returns slice of current Hardware addresses. | ||
| func (s *SetTTL) Slice() []net.HardwareAddr { | ||
| s.retrieveSignal <- struct{}{} | ||
| return <-s.macSlice | ||
| } | ||
|
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||
| func delMac(val string, c chan string) func() { | ||
| return func() { | ||
| c <- val | ||
| } | ||
| } | ||
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| // daemon runs infinite loop that will end when | ||
| // given context will be done. | ||
| func (s *SetTTL) daemon(ctx context.Context) { | ||
| // oh boy, here starts fun: infinite select loop | ||
| // with different branches | ||
| for { | ||
| // lets select from multiple channels | ||
| // attached to given set, this way | ||
| // we can ensure that everything | ||
| // will be synced together | ||
| select { | ||
| case newMac := <-s.toAdd: | ||
| // first scenario, client want to | ||
| // ad new mac address to set | ||
|
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| // lets check if new mac address is already in the | ||
| // map | ||
| if timer, contains := s.m[newMac.value]; contains { | ||
| // if it is, reset timer with given ttl value | ||
| timer.Reset(newMac.ttl) | ||
| } else { | ||
| // if given mac address is not present | ||
| // at the map, lets create new timer | ||
| // that will send delete signal to our | ||
| // daemon | ||
| s.m[newMac.value] = time.AfterFunc( | ||
| newMac.ttl, | ||
| delMac(newMac.value, s.toDel), | ||
| ) | ||
| } | ||
| case toDel := <-s.toDel: | ||
| // simple scenario: delete received mac | ||
| // from our map and go on | ||
| delete(s.m, toDel) | ||
| case <-s.retrieveSignal: | ||
| // we've just received retrieveSignal signal! | ||
| // lets allocate new slice that we will | ||
| // send to our client | ||
| res := make([]net.HardwareAddr, len(s.m), len(s.m)) | ||
|
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| // loop over collection of addresses. | ||
| index := 0 | ||
| for k := range s.m { | ||
| // we have to cast every key to net.HardwareAddr | ||
| // we can omit net.ParseMAC, because SetTTL permits | ||
| // only net.HardwareAddr to Push, so we assume here | ||
| // that client properly parsed HardwareAddr | ||
| res[index] = net.HardwareAddr(k) | ||
| index += 1 | ||
| } | ||
|
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| // send result to client | ||
| s.macSlice <- res | ||
| case <-ctx.Done(): | ||
| // context is Done, so we're closing channel and | ||
| // return to escape from loop | ||
| close(s.toAdd) | ||
| close(s.toDel) | ||
| close(s.retrieveSignal) | ||
| close(s.macSlice) | ||
| return | ||
| } | ||
|
|
||
| // there are no mutexes lol | ||
| } | ||
| } |
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