Tablet throttler: remove LowPriority logic (#16013)

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

Author: shlomi-noach

go/vt/vttablet/tabletmanager/rpc_throttler.go

@@ -34,7 +34,6 @@ func (tm *TabletManager) CheckThrottler(ctx context.Context, req *tabletmanagerd
 		req.AppName = throttlerapp.VitessName.String()
 	}
 	flags := &throttle.CheckFlags{
-		LowPriority:           false,
 		SkipRequestHeartbeats: true,
 	}
 	checkResult := tm.QueryServiceControl.CheckThrottler(ctx, req.AppName, flags)

go/vt/vttablet/tabletserver/tabletserver.go

@@ -1896,7 +1896,6 @@ func (tsv *TabletServer) registerThrottlerCheckHandlers() {
 				appName = throttlerapp.DefaultName.String()
 			}
 			flags := &throttle.CheckFlags{
-				LowPriority:           (r.URL.Query().Get("p") == "low"),
 				SkipRequestHeartbeats: (r.URL.Query().Get("s") == "true"),
 			}
 			checkResult := tsv.lagThrottler.CheckByType(ctx, appName, remoteAddr, flags, checkType)

go/vt/vttablet/tabletserver/throttle/check.go

@@ -67,7 +67,6 @@ var (
 type CheckFlags struct {
 	ReadCheck             bool
 	OverrideThreshold     float64
-	LowPriority           bool
 	OKIfNotExists         bool
 	SkipRequestHeartbeats bool
 }
@@ -91,14 +90,6 @@ func NewThrottlerCheck(throttler *Throttler) *ThrottlerCheck {
 func (check *ThrottlerCheck) checkAppMetricResult(ctx context.Context, appName string, storeType string, storeName string, metricResultFunc base.MetricResultFunc, flags *CheckFlags) (checkResult *CheckResult) {
 	// Handle deprioritized app logic
 	denyApp := false
-	metricName := fmt.Sprintf("%s/%s", storeType, storeName)
-	if flags.LowPriority {
-		if _, exists := check.throttler.nonLowPriorityAppRequestsThrottled.Get(metricName); exists {
-			// a non-deprioritized app, ie a "normal" app, has recently been throttled.
-			// This is now a deprioritized app. Deny access to this request.
-			denyApp = true
-		}
-	}
 	//
 	metricResult, threshold := check.throttler.AppRequestMetricResult(ctx, appName, metricResultFunc, denyApp)
 	if flags.OverrideThreshold > 0 {
@@ -125,11 +116,6 @@ func (check *ThrottlerCheck) checkAppMetricResult(ctx context.Context, appName s
 		// casual throttling
 		statusCode = http.StatusTooManyRequests // 429
 		err = base.ErrThresholdExceeded
-
-		if !flags.LowPriority && !flags.ReadCheck && throttlerapp.VitessName.Equals(appName) {
-			// low priority requests will henceforth be denied
-			go check.throttler.nonLowPriorityAppRequestsThrottled.SetDefault(metricName, true)
-		}
 	default:
 		// all good!
 		statusCode = http.StatusOK // 200

go/vt/vttablet/tabletserver/throttle/client.go

@@ -56,30 +56,14 @@ type Client struct {
 	lastSuccessfulThrottle   int64
 }
 
-// NewProductionClient creates a client suitable for foreground/production jobs, which have normal priority.
-func NewProductionClient(throttler *Throttler, appName throttlerapp.Name, checkType ThrottleCheckType) *Client {
-	initThrottleTicker()
-	return &Client{
-		throttler: throttler,
-		appName:   appName,
-		checkType: checkType,
-		flags: CheckFlags{
-			LowPriority: false,
-		},
-	}
-}
-
-// NewBackgroundClient creates a client suitable for background jobs, which have low priority over production traffic,
-// e.g. migration, table pruning, vreplication
+// NewBackgroundClient creates a client
 func NewBackgroundClient(throttler *Throttler, appName throttlerapp.Name, checkType ThrottleCheckType) *Client {
 	initThrottleTicker()
 	return &Client{
 		throttler: throttler,
 		appName:   appName,
 		checkType: checkType,
-		flags: CheckFlags{
-			LowPriority: true,
-		},
+		flags:     CheckFlags{},
 	}
 }
 

go/vt/vttablet/tabletserver/throttle/throttler.go

@@ -93,8 +93,6 @@ const (
 	aggregatedMetricsExpiration = 5 * time.Second
 	recentAppsExpiration        = time.Hour * 24
 
-	nonDeprioritizedAppMapExpiration = time.Second
-
 	dormantPeriod              = time.Minute // How long since last check to be considered dormant
 	DefaultAppThrottleDuration = time.Hour
 	DefaultThrottleRatio       = 1.0
@@ -208,8 +206,7 @@ type Throttler struct {
 
 	readSelfThrottleMetric func(context.Context, *mysql.Probe) *mysql.MySQLThrottleMetric // overwritten by unit test
 
-	nonLowPriorityAppRequestsThrottled *cache.Cache
-	httpClient                         *http.Client
+	httpClient *http.Client
 }
 
 // ThrottlerStatus published some status values from the throttler
@@ -256,7 +253,6 @@ func NewThrottler(env tabletenv.Env, srvTopoServer srvtopo.Server, ts *topo.Serv
 	throttler.aggregatedMetrics = cache.New(aggregatedMetricsExpiration, 0)
 	throttler.recentApps = cache.New(recentAppsExpiration, 0)
 	throttler.metricsHealth = cache.New(cache.NoExpiration, 0)
-	throttler.nonLowPriorityAppRequestsThrottled = cache.New(nonDeprioritizedAppMapExpiration, 0)
 
 	throttler.httpClient = base.SetupHTTPClient(2 * mysqlCollectInterval)
 	throttler.initThrottleTabletTypes()
@@ -728,7 +724,6 @@ func (throttler *Throttler) Operate(ctx context.Context, wg *sync.WaitGroup) {
 			primaryStimulatorRateLimiter.Stop()
 			throttler.aggregatedMetrics.Flush()
 			throttler.recentApps.Flush()
-			throttler.nonLowPriorityAppRequestsThrottled.Flush()
 			wg.Done()
 		}()
 		// we do not flush throttler.throttledApps because this is data submitted by the user; the user expects the data to survive a disable+enable

go/vt/vttablet/tabletserver/throttle/throttler_test.go

@@ -157,7 +157,6 @@ func newTestThrottler() *Throttler {
 	throttler.aggregatedMetrics = cache.New(10*aggregatedMetricsExpiration, 0)
 	throttler.recentApps = cache.New(recentAppsExpiration, 0)
 	throttler.metricsHealth = cache.New(cache.NoExpiration, 0)
-	throttler.nonLowPriorityAppRequestsThrottled = cache.New(nonDeprioritizedAppMapExpiration, 0)
 	throttler.metricsQuery.Store(metricsQuery)
 	throttler.initThrottleTabletTypes()
 	throttler.check = NewThrottlerCheck(throttler)