Improve Continuous integration and fix concurrency bugs (#66)

- improvements to the continuous GH actions
- fix edge case concurrency bugs with Process.start() and state transitions discovered setting up CI.

.github/workflows/go-ci.yml

@@ -1,10 +1,11 @@
 # This workflow will build a golang project
 
-name: Go
+name: CI
 
 on:
   push:
     branches: [ "main" ]
+
   pull_request:
     branches: [ "main" ]
 
@@ -13,7 +14,7 @@ on:
 
 jobs:
 
-  build:
+  run-tests:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
@@ -23,5 +24,9 @@ jobs:
       with:
         go-version: '1.23'
 
-    - name: Test
+    # necessary for testing proxy/Process swapping
+    - name: Create simple-responder
+      run: make simple-responder
+
+    - name: Test all
       run: make test-all

proxy/process.go

@@ -133,9 +133,24 @@ func (p *Process) start() error {
 		return nil
 	}
 
+	// There is the possibility of a hard to replicate race condition where
+	// curState *WAS* StateStopped but by the time we get to the p.stateMutex.Lock()
+	// below, it's value has changed!
+
 	p.stateMutex.Lock()
 	defer p.stateMutex.Unlock()
 
+	// with the exclusive lock, check if p.state is StateStopped, which is the only valid state
+	// to transition from to StateReady
+
+	if p.state != StateStopped {
+		if p.state == StateReady {
+			return nil
+		} else {
+			return fmt.Errorf("start() can not proceed expected StateReady but process is in %v", p.state)
+		}
+	}
+
 	if err := p.setState(StateStarting); err != nil {
 		return err
 	}

proxy/process_test.go

@@ -169,6 +169,8 @@ func TestProcess_LowTTLValue(t *testing.T) {
 }
 
 // issue #19
+// This test makes sure using Process.Stop() does not affect pending HTTP
+// requests. All HTTP requests in this test should complete successfully.
 func TestProcess_HTTPRequestsHaveTimeToFinish(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping slow test")
@@ -192,8 +194,9 @@ func TestProcess_HTTPRequestsHaveTimeToFinish(t *testing.T) {
 		wg.Add(1)
 		go func(key string) {
 			defer wg.Done()
-			// send a request that should take 5 * 200ms (1 second) to complete
+			// send a request where simple-responder is will wait 300ms before responding
-			req := httptest.NewRequest("GET", fmt.Sprintf("/slow-respond?echo=%s&delay=200ms", key), nil)
+			// this will simulate an in-progress request.
+			req := httptest.NewRequest("GET", fmt.Sprintf("/slow-respond?echo=%s&delay=300ms", key), nil)
 			w := httptest.NewRecorder()
 
 			process.ProxyRequest(w, req)
@@ -209,9 +212,9 @@ func TestProcess_HTTPRequestsHaveTimeToFinish(t *testing.T) {
 		}(key)
 	}
 
-	// stop the requests in the middle
+	// Stop the process while requests are still being processed
 	go func() {
-		<-time.After(500 * time.Millisecond)
+		<-time.After(150 * time.Millisecond)
 		process.Stop()
 	}()