Add Permanent Throttle Option (#170)

Update freno to support infinite TTL

Author: kristinaElizDev

doc/mysql-backend.md

@@ -78,7 +78,7 @@ CREATE TABLE service_election (
 CREATE TABLE throttled_apps (
   app_name varchar(128) NOT NULL,
 	throttled_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
-  expires_at TIMESTAMP NOT NULL,
+  expires_at TIMESTAMP,
 	ratio DOUBLE,
   PRIMARY KEY (app_name)
 );

pkg/group/mysql.go

@@ -24,7 +24,7 @@ service_id varchar(128) NOT NULL,
 CREATE TABLE throttled_apps (
   app_name varchar(128) NOT NULL,
 	throttled_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
-  expires_at TIMESTAMP NOT NULL,
+  expires_at TIMESTAMP,
 	ratio DOUBLE,
   PRIMARY KEY (app_name)
 );
@@ -346,7 +346,7 @@ func (backend *MySQLBackend) readThrottledApps() error {
 	query := `
 		select
 			app_name,
-			timestampdiff(second, now(), expires_at) as ttl_seconds,
+			timestampdiff(second, now(), coalesce(expires_at,now())) as ttl_seconds,
 			ratio
 		from
 			throttled_apps
@@ -357,6 +357,9 @@ func (backend *MySQLBackend) readThrottledApps() error {
 		ttlSeconds := m.GetInt64("ttl_seconds")
 		ratio, _ := strconv.ParseFloat(m.GetString("ratio"), 64)
 		expiresAt := time.Now().Add(time.Duration(ttlSeconds) * time.Second)
+		if ttlSeconds == 0 {
+			expiresAt = time.Time{}
+		}
 
 		go log.Debugf("read-throttled-apps: app=%s, ttlSeconds%+v, expiresAt=%+v, ratio=%+v", appName, ttlSeconds, expiresAt, ratio)
 		go backend.throttler.ThrottleApp(appName, expiresAt, ratio)
@@ -398,18 +401,19 @@ func (backend *MySQLBackend) ThrottleApp(appName string, ttlMinutes int64, expir
 	  `
 		args = sqlutils.Args(appName, ttlMinutes, ratio)
 	} else {
-		// TTL=0 ; if app is already throttled, keep existing TTL and only update ratio.
-		// if app does not exist use DefaultThrottleTTL
+		// TTL=0 ; if app is already throttled, update throttle to infinity and update ratio.
+		// if app does not exist, TTL should be infinite
 		query = `
 	    insert into throttled_apps (
-	        app_name, throttled_at, expires_at, ratio
+	        app_name, throttled_at, ratio
 	      ) values (
-	        ?, now(), now() + interval ? minute, ?
+	        ?, now(), ?
 	      )
 			on duplicate key update
-				ratio=values(ratio)
+				ratio=values(ratio),
+				expires_at=null
 		`
-		args = sqlutils.Args(appName, throttle.DefaultThrottleTTLMinutes, ratio)
+		args = sqlutils.Args(appName, ratio)
 	}
 	_, err := sqlutils.ExecNoPrepare(backend.db, query, args...)
 	backend.throttler.ThrottleApp(appName, expireAt, ratio)

pkg/throttle/throttler.go

@@ -41,7 +41,6 @@ const skippedHostsSnapshotInterval = 5 * time.Second
 const nonDeprioritizedAppMapExpiration = time.Second
 const nonDeprioritizedAppMapInterval = 100 * time.Millisecond
 
-const DefaultThrottleTTLMinutes = 60
 const DefaultSkipTTLMinutes = 60
 const DefaultThrottleRatio = 1.0
 
@@ -519,21 +518,24 @@ func (throttler *Throttler) ThrottleApp(appName string, expireAt time.Time, rati
 		appThrottle = object.(*base.AppThrottle)
 		if !expireAt.IsZero() {
 			appThrottle.ExpireAt = expireAt
+		} else {
+			appThrottle.ExpireAt = time.Time{}
 		}
 		if ratio >= 0 {
 			appThrottle.Ratio = ratio
 		}
 	} else {
-		if expireAt.IsZero() {
-			expireAt = now.Add(DefaultThrottleTTLMinutes * time.Minute)
-		}
 		if ratio < 0 {
 			ratio = DefaultThrottleRatio
 		}
 		appThrottle = base.NewAppThrottle(expireAt, ratio)
 	}
-	if now.Before(appThrottle.ExpireAt) {
-		throttler.throttledApps.Set(appName, appThrottle, cache.DefaultExpiration)
+	
+	if expireAt.IsZero() {
+		//If expires at is zero, update the store to never expire the throttle
+		throttler.throttledApps.Set(appName, appThrottle, -1)
+	} else if now.Before(appThrottle.ExpireAt) {
+			throttler.throttledApps.Set(appName, appThrottle, cache.DefaultExpiration)
 	} else {
 		throttler.UnthrottleApp(appName)
 	}