ifname: avoid unpredictable conditions in getMap test (influxdata#7848)

Author: reimda

plugins/processors/ifname/ifname.go

@@ -111,8 +111,7 @@ type IfName struct {
 
 	gsBase snmp.GosnmpWrapper `toml:"-"`
 
-	sigs     sigMap     `toml:"-"`
-	sigsLock sync.Mutex `toml:"-"`
+	sigs sigMap `toml:"-"`
 }
 
 const minRetry time.Duration = 5 * time.Minute
@@ -251,14 +250,14 @@ func (d *IfName) getMap(agent string) (entry nameMap, age time.Duration, err err
 	}
 
 	// Is this the first request for this agent?
-	d.sigsLock.Lock()
+	d.rwLock.Lock()
 	sig, found := d.sigs[agent]
 	if !found {
 		s := make(chan struct{})
 		d.sigs[agent] = s
 		sig = s
 	}
-	d.sigsLock.Unlock()
+	d.rwLock.Unlock()
 
 	if found {
 		// This is not the first request.  Wait for first to finish.
@@ -281,24 +280,21 @@ func (d *IfName) getMap(agent string) (entry nameMap, age time.Duration, err err
 	m, err = d.getMapRemote(agent)
 	if err != nil {
 		//failure.  signal without saving to cache
-		d.sigsLock.Lock()
+		d.rwLock.Lock()
 		close(sig)
 		delete(d.sigs, agent)
-		d.sigsLock.Unlock()
+		d.rwLock.Unlock()
 
 		return nil, 0, fmt.Errorf("getting remote table: %w", err)
 	}
 
-	// Cache it
+	// Cache it, then signal any other waiting requests for this agent
+	// and clean up
 	d.rwLock.Lock()
 	d.cache.Put(agent, m)
-	d.rwLock.Unlock()
-
-	// Signal any other waiting requests for this agent and clean up
-	d.sigsLock.Lock()
 	close(sig)
 	delete(d.sigs, agent)
-	d.sigsLock.Unlock()
+	d.rwLock.Unlock()
 
 	return m, 0, nil
 }

plugins/processors/ifname/ifname_test.go

@@ -26,7 +26,7 @@ func TestTable(t *testing.T) {
 
 	config := snmp.ClientConfig{
 		Version: 2,
-		Timeout: internal.Duration{Duration: 5 * time.Second}, // doesn't work with 0 timeout
+		Timeout: internal.Duration{Duration: 5 * time.Second}, // Doesn't work with 0 timeout
 	}
 	gs, err := snmp.NewWrapper(config)
 	require.NoError(t, err)
@@ -36,7 +36,7 @@ func TestTable(t *testing.T) {
 	err = gs.Connect()
 	require.NoError(t, err)
 
-	//could use ifIndex but oid index is always the same
+	// Could use ifIndex but oid index is always the same
 	m, err := buildMap(gs, tab, "ifDescr")
 	require.NoError(t, err)
 	require.NotEmpty(t, m)
@@ -53,7 +53,7 @@ func TestIfName(t *testing.T) {
 		CacheSize: 1000,
 		ClientConfig: snmp.ClientConfig{
 			Version: 2,
-			Timeout: internal.Duration{Duration: 5 * time.Second}, // doesn't work with 0 timeout
+			Timeout: internal.Duration{Duration: 5 * time.Second}, // Doesn't work with 0 timeout
 		},
 	}
 	err := d.Init()
@@ -93,65 +93,52 @@ func TestIfName(t *testing.T) {
 
 func TestGetMap(t *testing.T) {
 	d := IfName{
-		SourceTag: "ifIndex",
-		DestTag:   "ifName",
-		AgentTag:  "agent",
 		CacheSize: 1000,
-		ClientConfig: snmp.ClientConfig{
-			Version: 2,
-			Timeout: internal.Duration{Duration: 5 * time.Second}, // doesn't work with 0 timeout
-		},
-		CacheTTL: config.Duration(10 * time.Second),
+		CacheTTL:  config.Duration(10 * time.Second),
 	}
 
-	// This test mocks the snmp transaction so don't run net-snmp
-	// commands to look up table names.
+	// Don't run net-snmp commands to look up table names.
 	d.makeTable = func(agent string) (*si.Table, error) {
 		return &si.Table{}, nil
 	}
 	err := d.Init()
 	require.NoError(t, err)
 
-	// Request the same agent multiple times in goroutines. The first
-	// request should make the mocked remote call and the others
-	// should block until the response is cached, then return the
-	// cached response.
-
 	expected := nameMap{
 		1: "ifname1",
 		2: "ifname2",
 	}
 
-	var wgRemote sync.WaitGroup
 	var remoteCalls int32
 
-	wgRemote.Add(1)
+	// Mock the snmp transaction
 	d.getMapRemote = func(agent string) (nameMap, error) {
 		atomic.AddInt32(&remoteCalls, 1)
-		wgRemote.Wait() //don't return until all requests are made
 		return expected, nil
 	}
+	m, age, err := d.getMap("agent")
+	require.NoError(t, err)
+	require.Zero(t, age) // Age is zero when map comes from getMapRemote
+	require.Equal(t, expected, m)
 
-	const thMax = 3
-	var wgReq sync.WaitGroup
+	// Remote call should happen the first time getMap runs
+	require.Equal(t, int32(1), remoteCalls)
 
+	var wg sync.WaitGroup
+	const thMax = 3
 	for th := 0; th < thMax; th++ {
-		wgReq.Add(1)
+		wg.Add(1)
 		go func() {
-			defer wgReq.Done()
-			m, _, err := d.getMap("agent")
+			defer wg.Done()
+			m, age, err := d.getMap("agent")
 			require.NoError(t, err)
+			require.NotZero(t, age) // Age is nonzero when map comes from cache
 			require.Equal(t, expected, m)
 		}()
 	}
 
-	//signal mocked remote call to finish
-	wgRemote.Done()
-
-	//wait for requests to finish
-	wgReq.Wait()
+	wg.Wait()
 
-	//remote call should only happen once
+	// Remote call should not happen subsequent times getMap runs
 	require.Equal(t, int32(1), remoteCalls)
-
 }