Candidates & Contexts Code Samples

[dm03514]

HTTP Handler - Non-Synchronized Counter

	counter := 0

	go func() {
		http.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			counter = counter + 1 # line 28
			fmt.Printf("handling request: %d\n", counter)
			fmt.Fprintln(w, "Hello, client")
		}))
		log.Fatal(http.ListenAndServe(":8080", nil))
	}()

Explicit Race Condition Test - Counting to 10000 - 200 concurrent requesters

$ go test -run TestExplicitRace ./races/ -v -total-requests=10000 -concurrent-requests=200
=== RUN   TestExplicitRace
Num Requests TO Make: 10000
Final Count: 9884
    TestExplicitRace: explicit_test.go:69: expected 10000 requests: received 9884
--- FAIL: TestExplicitRace (1.35s)
FAIL
FAIL    github.com/dm03514/grokking-go/candidates-and-contexts/races    1.475s
FAIL

Explicit Race - Race Detector

$ go test -run TestExplicitRace ./races/ -v -total-requests=10000 -concurrent-requests=200 -race
=== RUN   TestExplicitRace
==================
WARNING: DATA RACE
Read at 0x00c000128350 by goroutine 550:
  github.com/dm03514/grokking-go/candidates-and-contexts/races.TestExplicitRace.func1.1()
      /Users/danielmican/go/src/github.com/dm03514/grokking-go/candidates-and-contexts/races/explicit_test.go:28 +0x4a
  net/http.HandlerFunc.ServeHTTP()
      /usr/local/Cellar/go/1.14.4/libexec/src/net/http/server.go:2012 +0x51
  net/http.(*ServeMux).ServeHTTP()
      /usr/local/Cellar/go/1.14.4/libexec/src/net/http/server.go:2387 +0x288
  net/http.serverHandler.ServeHTTP()
      /usr/local/Cellar/go/1.14.4/libexec/src/net/http/server.go:2807 +0xce
  net/http.(*conn).serve()
      /usr/local/Cellar/go/1.14.4/libexec/src/net/http/server.go:1895 +0x837

Previous write at 0x00c000128350 by goroutine 491:
  github.com/dm03514/grokking-go/candidates-and-contexts/races.TestExplicitRace.func1.1()
      /Users/danielmican/go/src/github.com/dm03514/grokking-go/candidates-and-contexts/races/explicit_test.go:28 +0x60
  net/http.HandlerFunc.ServeHTTP()
      /usr/local/Cellar/go/1.14.4/libexec/src/net/http/server.go:2012 +0x51
  net/http.(*ServeMux).ServeHTTP()
      /usr/local/Cellar/go/1.14.4/libexec/src/net/http/server.go:2387 +0x288
  net/http.serverHandler.ServeHTTP()
      /usr/local/Cellar/go/1.14.4/libexec/src/net/http/server.go:2807 +0xce
  net/http.(*conn).serve()
      /usr/local/Cellar/go/1.14.4/libexec/src/net/http/server.go:1895 +0x837

HTTP Handler - Synchronized Counter - SUCCESS

	var mu = new(sync.Mutex)
	counter := 0

	go func() {
		http.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			mu.Lock()
			defer mu.Unlock()
			counter = counter + 1

			fmt.Fprintln(w, "Hello, client")
		}))
		log.Fatal(http.ListenAndServe(":8080", nil))
	}()

$ go test -run TestSynchronizedMutexNoRace ./races/ -v -total-requests=10000 -concurrent-requests=200

=== RUN   TestSynchronizedMutexNoRace
Num Requests TO Make: 10000
Final Count: 10000
--- PASS: TestSynchronizedMutexNoRace (0.86s)
PASS
ok      github.com/dm03514/grokking-go/candidates-and-contexts/races    0.986s

Race Detector

$ go test -run TestSynchronizedMutexNoRace ./races/ -v -total-requests=10000 -concurrent-requests=200 -race
=== RUN   TestSynchronizedMutexNoRace
Num Requests TO Make: 10000
Final Count: 10000
--- PASS: TestSynchronizedMutexNoRace (4.27s)
PASS
ok      github.com/dm03514/grokking-go/candidates-and-contexts/races    4.476s

HTTP Handler - Monitor Pattern - SUCCESS

type CounterMonitor struct {
	count int
}

func (cm *CounterMonitor) Monitor(c chan struct{}) {
	for range c {
		cm.count = cm.count + 1
	}
}

func (cm *CounterMonitor) Count() int {
	return cm.count
}

	countChan := make(chan struct{})

	cm := &CounterMonitor{}
	go cm.Monitor(countChan)

	go func() {
		http.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			fmt.Fprintln(w, "Hello, client")
			countChan <- struct{}{}
		}))
		log.Fatal(http.ListenAndServe(":8080", nil))
	}()

Monitor Test - SUCCESS! - Multiple Concurrent Producers - Single Consumer

$ go test -run TestMonitorNoRace ./races/ -v -total-requests=10000 -concurrent-requests=200
=== RUN   TestMonitorNoRace
Num Requests TO Make: 10000
Final Count: 10000
--- PASS: TestMonitorNoRace (0.68s)
PASS
ok      github.com/dm03514/grokking-go/candidates-and-contexts/races    0.804s