Reputation: 79
the below code that get worker from channel and execute function "call", all routines finish and print that they are done but wait never finishes, i traced the counter of WaitGroup by making varible counter incresing when add to wg and decresing when done and it was zero at the end of for loop any help please
package mapreduce
import (
"fmt"
"sync"
)
func schedule(jobName string, mapFiles []string, nReduce int, phase jobPhase, registerChan chan string) {
var ntasks int
var n_other int // number of inputs (for reduce) or outputs (for map)
switch phase {
case mapPhase:
ntasks = len(mapFiles)
n_other = nReduce
case reducePhase:
ntasks = nReduce
n_other = len(mapFiles)
}
fmt.Printf("Schedule: %v %v tasks (%d I/Os)\n", ntasks, phase, n_other)
var wg sync.WaitGroup
for i := 0; i < ntasks; i++ {
worker := <-registerChan
doTaskArg := DoTaskArgs{jobName, mapFiles[i], phase, i, n_other}
wg.Add(1)
go func() {
defer wg.Done()
done := call(worker, "Worker.DoTask", doTaskArg, nil)
if done {
registerChan <- worker
} else {
i = i - 1
}
}()
}
wg.Wait()
fmt.Printf("Schedule: %v phase done\n", phase)
}
Upvotes: 1
Views: 3126
Reputation: 5914
The channel is blocking your goroutine. If you put some data into a unbuffered channel the goroutine waits until the receiver gets the the data from the channel. In your case your routine blocks at register <- worker
and defer wg.Done()
is never called, because the function is waiting.
Upvotes: 4