Function checkRoundRobinRPCs

balancer/leastrequest/leastrequest_test.go:165–198

checkRoundRobinRPCs verifies that EmptyCall RPCs on the given ClientConn, connected to a server exposing the test.grpc_testing.TestService, are roundrobined across the given backend addresses. Returns a non-nil error if context deadline expires before RPCs start to get roundrobined across the given

(ctx context.Context, client testgrpc.TestServiceClient, addrs []resolver.Address)

// Returns a non-nil error if context deadline expires before RPCs start to get
// roundrobined across the given backends.
func checkRoundRobinRPCs(ctx context.Context, client testgrpc.TestServiceClient, addrs []resolver.Address) error {
	wantAddrCount := make(map[string]int)
	for _, addr := range addrs {
		wantAddrCount[addr.Addr]++
	}
	gotAddrCount := make(map[string]int)
	for ; ctx.Err() == nil; <-time.After(time.Millisecond) {
		gotAddrCount = make(map[string]int)
		// Perform 3 iterations.
		var iterations [][]string
		for i := 0; i < 3; i++ {
			iteration := make([]string, len(addrs))
			for c := 0; c < len(addrs); c++ {
				var peer peer.Peer
				client.EmptyCall(ctx, &testpb.Empty{}, grpc.Peer(&peer))
				iteration[c] = peer.Addr.String()
			}
			iterations = append(iterations, iteration)
		}
		// Ensure the first iteration contains all addresses in addrs.
		for _, addr := range iterations[0] {
			gotAddrCount[addr]++
		}
		if !cmp.Equal(gotAddrCount, wantAddrCount) {
			continue
		}
		// Ensure all three iterations contain the same addresses.
		if !cmp.Equal(iterations[0], iterations[1]) || !cmp.Equal(iterations[0], iterations[2]) {
			continue
		}
		return nil
	}
	return fmt.Errorf("timeout when waiting for roundrobin distribution of RPCs across addresses: %v; got: %v", addrs, gotAddrCount)
}

// TestLeastRequestE2E tests the Least Request LB policy in an e2e style. The
// Least Request balancer is configured as the top level balancer of the