A channel multiplexer

Question

Note - newbie in Go.

I\'ve written a multiplexer that should merge the outputs of an array of channels into one. Happy with constructive criticism.<

Answer 1

A bit after the fact, I know, but I wrote a package which implements a generic Multiplex function similar to this one. It uses the "select" call in the reflection package to ensure efficient and balanced multiplexing without any need for a lock or wait group.

• Code: https://github.com/eapache/channels
• Documentation: https://godoc.org/github.com/eapache/channels

Answer 2

Each of your goroutines spawned from Mux ends up pulling from the same channel, since c gets updated on each iteration of the loop – they don't just capture the value of c. You will get the expected results if you pass the channel to the goroutine like so:

for _, c := range channels {
    go func(c <-chan big.Int) {
        ...
    }(c)
}

You can test this modification here.

One other possible problem is your handling of the n variable: if you're running with GOMAXPROCS != 1, you could have two goroutines trying to update it at once. The sync.WaitGroup type would be a safer way to wait for goroutines to complete.

Answer 3

To build on James Hentridge answer, an idiomatic way to handle the re-assignement problem when using the range statement is to assign a local variable to the value at stake:

for _, c := range channels {
    c := c
    go func() {
    ...
    }()
}