Pass PickOpts by value

Signed-off-by: Mohamed Hamza <mhamza15@github.com>

Author: mhamza15

go/vt/vtgate/balancer/balancer.go

@@ -90,7 +90,7 @@ converge on the desired balanced query load.
 type TabletBalancer interface {
 	// Pick is the main entry point to the balancer. Returns the best tablet out of the list
 	// for a given query to maintain the desired balanced allocation over multiple executions.
-	Pick(target *querypb.Target, tablets []*discovery.TabletHealth, opts *PickOpts) *discovery.TabletHealth
+	Pick(target *querypb.Target, tablets []*discovery.TabletHealth, opts PickOpts) *discovery.TabletHealth
 
 	// DebugHandler provides a summary of tablet balancer state
 	DebugHandler(w http.ResponseWriter, r *http.Request)
@@ -176,7 +176,7 @@ func (b *tabletBalancer) DebugHandler(w http.ResponseWriter, _ *http.Request) {
 // Given the total allocation for the set of tablets, choose the best target
 // by a weighted random sample so that over time the system will achieve the
 // desired balanced allocation.
-func (b *tabletBalancer) Pick(target *querypb.Target, tablets []*discovery.TabletHealth, _ *PickOpts) *discovery.TabletHealth {
+func (b *tabletBalancer) Pick(target *querypb.Target, tablets []*discovery.TabletHealth, _ PickOpts) *discovery.TabletHealth {
 	numTablets := len(tablets)
 	if numTablets == 0 {
 		return nil

go/vt/vtgate/balancer/balancer_test.go

@@ -298,7 +298,7 @@ func TestBalancedPick(t *testing.T) {
 			b := NewTabletBalancer(localCell, vtGateCells).(*tabletBalancer)
 
 			for i := 0; i < N/len(vtGateCells); i++ {
-				th := b.Pick(target, tablets, nil)
+				th := b.Pick(target, tablets, PickOpts{})
 				if i == 0 {
 					t.Logf("Target Flows %v, Balancer: %s\n", expectedPerCell, b.print())
 				}
@@ -336,7 +336,7 @@ func TestTopologyChanged(t *testing.T) {
 	tablets = tablets[0:2]
 
 	for i := 0; i < N; i++ {
-		th := b.Pick(target, tablets, nil)
+		th := b.Pick(target, tablets, PickOpts{})
 		allocation, totalAllocation := b.getAllocation(target, tablets)
 
 		assert.Equalf(t, ALLOCATION/2, totalAllocation, "totalAllocation mismatch %s", b.print())
@@ -346,7 +346,7 @@ func TestTopologyChanged(t *testing.T) {
 
 	// Run again with the full topology. Now traffic should go to cell b
 	for i := 0; i < N; i++ {
-		th := b.Pick(target, allTablets, nil)
+		th := b.Pick(target, allTablets, PickOpts{})
 
 		allocation, totalAllocation := b.getAllocation(target, allTablets)
 
@@ -359,7 +359,7 @@ func TestTopologyChanged(t *testing.T) {
 	newTablet := createTestTablet("b")
 	allTablets[2] = newTablet
 	for i := 0; i < N; i++ {
-		th := b.Pick(target, allTablets, nil)
+		th := b.Pick(target, allTablets, PickOpts{})
 
 		allocation, totalAllocation := b.getAllocation(target, allTablets)
 

go/vt/vtgate/balancer/session.go

@@ -93,8 +93,8 @@ func NewSessionBalancer(ctx context.Context, localCell string, topoServer srvtop
 //
 // For a given session, it will return the same tablet for its duration, with preference to tablets
 // in the local cell.
-func (b *SessionBalancer) Pick(target *querypb.Target, _ []*discovery.TabletHealth, opts *PickOpts) *discovery.TabletHealth {
-	if opts == nil {
+func (b *SessionBalancer) Pick(target *querypb.Target, _ []*discovery.TabletHealth, opts PickOpts) *discovery.TabletHealth {
+	if opts.SessionUUID == "" {
 		return nil
 	}
 

go/vt/vtgate/balancer/session_test.go

@@ -508,8 +508,8 @@ func TestPickNoOpts(t *testing.T) {
 	// Give a moment for the worker to process the tablets
 	time.Sleep(10 * time.Millisecond)
 
-	// Test with nil opts
-	result := b.Pick(target, nil, nil)
+	// Test with empty opts
+	result := b.Pick(target, nil, PickOpts{})
 	require.Nil(t, result)
 }
 
@@ -681,6 +681,6 @@ func TestTabletTypesToWatch(t *testing.T) {
 	}
 }
 
-func buildOpts(uuid string) *PickOpts {
-	return &PickOpts{SessionUUID: uuid}
+func buildOpts(uuid string) PickOpts {
+	return PickOpts{SessionUUID: uuid}
 }

go/vt/vtgate/tabletgateway.go

@@ -436,7 +436,7 @@ func (gw *TabletGateway) getBalancerTablet(target *querypb.Target, tablets []*di
 			})
 		}
 
-		opts := &balancer.PickOpts{SessionUUID: opts.Options.SessionUUID, InvalidTablets: invalidTablets}
+		opts := balancer.PickOpts{SessionUUID: opts.Options.SessionUUID, InvalidTablets: invalidTablets}
 		tablet = gw.balancer.Pick(target, tablets, opts)
 	}