go: example of mutex usage

golang/mutex.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"sync"
+	"time"
+)
+
+const (
+	WRITE_ROUTINE_COUNT = 10
+	READ_ROUTINE_COUNT  = 10
+	MAP_SIZE            = 20
+)
+
+// Simulating reads and writes from different routines to a single map by locking the result map
+func main() {
+	var mutex = &sync.Mutex{}
+	var resource = make(map[int]int)
+
+	// Initializes map with 20 entries
+	for key := 0; key < MAP_SIZE; key++ {
+		resource[key] = 0
+	}
+
+	// Start write routines
+	for writeIdx := 0; writeIdx < WRITE_ROUTINE_COUNT; writeIdx++ {
+		go func() {
+			for {
+				// Generate random key based on the map size
+				key := rand.Intn(MAP_SIZE)
+				// Generate random values
+				val := rand.Intn(1000)
+
+				// Lock before writing to map
+				mutex.Lock()
+				// Set/write map value
+				resource[key] = val
+				fmt.Printf("set map[%d] = %d\n", key, val)
+				// Unlock after write
+				mutex.Unlock()
+
+				// Simulate longer processing time
+				time.Sleep(time.Millisecond)
+			}
+		}()
+	}
+
+	// Start read routines
+	for readIdx := 0; readIdx < READ_ROUTINE_COUNT; readIdx++ {
+		go func() {
+			for {
+				// Generate random key based on the map size
+				key := rand.Intn(MAP_SIZE)
+
+				// Lock before writing to map
+				mutex.Lock()
+				// Read map value
+				val := resource[key]
+				fmt.Printf("get map[%d] = %d\n", key, val)
+				// Unlock after write
+				mutex.Unlock()
+
+				time.Sleep(time.Millisecond)
+			}
+		}()
+	}
+
+	// Allow the read/write routines to work for 2 seconds
+	time.Sleep(1 * time.Second)
+
+	// Print out final resource before exiting
+	fmt.Println("\nCurrent resource values:")
+	mutex.Lock()
+	for idx := 0; idx < MAP_SIZE; idx++ {
+		fmt.Printf("map[%d]=%d\n", idx, resource[idx])
+	}
+	mutex.Unlock()
+}