Golang Channels use cases
- 1. Channels Use Cases Erhan Yakut / @yakuter GopherCon Turkey / 18-19 December 2021
- 2. Programlama Dilleri Aktif olarak Go ile geliştirme yapmakla birlikte uzun yıllar PHP backend developer olarak proje geliştirdim. İletişim Bilgisi Eposta : yakuter@gmail.com Twitter: @yakuter İş / Görev Binalyze isimli Enterprise Forensics yazılım şirketinde Senior Software Architect olarak çalışmaktayım. Tecrübe/Bilgi Yaklaşık 15+ yıldır yazılım geliştirme ile ilgilenmekte olup, şu anda işletim sistemleri üzerinde olay sonrası delillerin toplanması için yazılım geliştirmekteyim. Erhan YAKUT (yakuter) Biyografi Ben Kimim?
- 3. Why do we need channels? Goroutines need to communicate each other to synchronize or exchange data with each other. The solution is channels.
- 4. What is channel? Channels are the pipes that connect concurrent goroutines. You can send values into channels from one goroutine and receive those values into another goroutine. Channels are a typed conduit through which you can send and receive values with the channel operator, <-. ch <- v // Send v to channel ch. v := <-ch // Receive from ch, and assign value to v. (The data flows in the direction of the arrow.) Like maps and slices, channels must be created before use: ch := make(chan int)
- 5. Closing channels Senders have the ability to close the channel to notify receivers that no more data will be sent on the channel. Receivers can use an additional variable while receiving data from the channel to check whether the channel has been closed. v, ok := <- ch If ok is false it means that we are reading from a closed channel. The value read from a closed channel will be the zero value of the channel's type. For example, if the channel is an int channel, then the value received from a closed channel will be 0. Only the sender should close a channel, never the receiver. Sending on a closed channel will cause a panic.
- 6. Buffered channels and range It is possible to create a channel with a buffer. Sends to a buffered channel are blocked only when the buffer is full. Similarly receives from a buffered channel are blocked only when the buffer is empty. Buffered channels can be created by passing an additional capacity parameter to the make function which specifies the size of the buffer. ch := make(chan type, capacity) The loop for v := range ch receives values from the channel repeatedly until it is closed.
- 7. Worker pool In computer programming, a worker pool is a software design pattern for achieving concurrency of execution in a computer program. A worker pool maintains multiple threads waiting for tasks to be allocated for concurrent execution by the supervising program.
- 8. Select usage The select statement is used to choose from multiple send/receive channel operations. The select statement blocks until one of the send/receive operations is ready. If multiple operations are ready, one of them is chosen at random. The syntax is similar to switch except that each of the case statements will be a channel operation.
- 9. Check context with select and ticker Tickers are for when you want to do something repeatedly at regular intervals. Tickers use a similar mechanism to timers: a channel that is sent values. In the example, we’ll use the select builtin on the channel to await the values as they arrive every interval.
- 10. Channels for notification 1-to-1 notification Notifications can be viewed as special requests/responses in which the responded values are not important. Generally, we use the blank struct type struct{} as the element types of the notification channels, for the size of type struct{} is zero, hence values of struct{} doesn't consume memory.
- 11. Start/stop signal If we queue up lots of goroutines, we can have them all start at the same time by closing the signal channel.
- 12. Start/stop signal with waitgroup To wait for multiple goroutines to finish, we can use a wait group. This WaitGroup is used to wait for all the goroutines launched here to finish. Note: if a WaitGroup is explicitly passed into functions, it should be done by pointer. Launch several goroutines and increment the WaitGroup counter for each. Avoid re-use of the same i value in each goroutine closure. https://go.dev/doc/faq#closures_and_goroutines
- 13. Scheduled notification We can use a timer or sleep function to wait for desired time and then send signal (notification) Please note, <-time.After(aDuration) will make the current goroutine enter blocking state, but a time.Sleep(aDuration) function call will not. The use of <-time.After(aDuration) is often used in the timeout mechanism which will be introduced below.
- 14. Use channels as mutex locks Channels are blocking actions. So we can use them as mutex locks. There are two manners to use one-capacity buffered channels as mutex locks. - Lock through a send, unlock through a receive. - Lock through a receive, unlock through a send. The following is a lock-through-send example.
- 15. Use channels as multi access mutexes Buffered channels can be used as multi access mutexes. If the capacity of a channel is N, then it can be viewed as a lock which can have most N owners at any time. Counting semaphores are often used to enforce a maximum number of concurrent requests.
- 16. Is channel closed An nice useful isClosed function
- 18. Thank You