Go Channel Patterns - Wait For Task

To improve my Go Programming skills and become a better Go engineer, I have recently purchased an excellent on-demand education from Ardan Labs. Materials are created by an expert Go engineer, Bill Kennedy.

I have decide to record my process of learning how to write more idiomatic code, following Go best practices and design philosophies.

This series of posts will describe channel patterns used for orchestration/signaling in Go via goroutines.

Wait For Task Pattern

The main idea behind Wait For Task pattern is to have:

a channel that provides a signaling semantics
a goroutine that waits for task so it can do some work
a goroutine that sends work to the previous goroutine

Example

In this example we have an employee (a goroutine) that doesn't know immediately what to do. The employee waits for manager to give him some work to do.
Once manager finds some work for the employee, it notifies employee by sending a signal (paper) via communication channel ch.

Feel free to try the example on Go Playground

package main

import (
    "fmt"
    "math/rand"
    "time"
)

func main() {
    // make channel of type string which provides signaling semantics
    // unbuffered channel provides a guarantee that the 
    // signal being sent is received
    ch := make(chan string)

    // goroutine 'a' that waits for some work => employee
    go func() {
        // employee waits for signal that it has some work to do
        p := <-ch
        fmt.Println("employee : received signal : ", p)
    }()

    // simulate the idea of unknown latency (do not use in production)
    // e.g. manager is thinking what work to pass to the employee
    time.Sleep(time.Duration(rand.Intn(500)) * time.Millisecond)


    // when work is ready, send signal form manager to the employee
    // sender (employee) has a guarantee that the worker (employee)
    // has received a signal
    ch <- "paper"

    fmt.Println("manager : sent signal")

    time.Sleep(time.Second)
}

Result (1st execution)

go run main.go
manager : sent signal
employee : received signal :  paper

Conclusion

In this article, wait for task channel pattern was described. In addition, simple implementation was provided.

Readers are encouraged to check out excellent Ardan Labs education materials to learn more.

Note

Depending on the country you are coming from, Ardan Labs education might be a little bit expensive. In that case you can always contact them and they will provide you a link to their scholarship form.

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