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balancer.go
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balancer.go
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/*
*
* Copyright 2020 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package testutils
import (
"context"
"errors"
"fmt"
"testing"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/resolver"
)
// TestSubConnsCount is the number of TestSubConns initialized as part of
// package init.
const TestSubConnsCount = 16
// testingLogger wraps the logging methods from testing.T.
type testingLogger interface {
Log(args ...interface{})
Logf(format string, args ...interface{})
}
// TestSubConns contains a list of SubConns to be used in tests.
var TestSubConns []*TestSubConn
func init() {
for i := 0; i < TestSubConnsCount; i++ {
TestSubConns = append(TestSubConns, &TestSubConn{
id: fmt.Sprintf("sc%d", i),
ConnectCh: make(chan struct{}, 1),
})
}
}
// TestSubConn implements the SubConn interface, to be used in tests.
type TestSubConn struct {
id string
ConnectCh chan struct{}
}
// UpdateAddresses is a no-op.
func (tsc *TestSubConn) UpdateAddresses([]resolver.Address) {}
// Connect is a no-op.
func (tsc *TestSubConn) Connect() {
select {
case tsc.ConnectCh <- struct{}{}:
default:
}
}
// String implements stringer to print human friendly error message.
func (tsc *TestSubConn) String() string {
return tsc.id
}
// TestClientConn is a mock balancer.ClientConn used in tests.
type TestClientConn struct {
logger testingLogger
NewSubConnAddrsCh chan []resolver.Address // the last 10 []Address to create subconn.
NewSubConnCh chan balancer.SubConn // the last 10 subconn created.
RemoveSubConnCh chan balancer.SubConn // the last 10 subconn removed.
UpdateAddressesAddrsCh chan []resolver.Address // last updated address via UpdateAddresses().
NewPickerCh chan balancer.Picker // the last picker updated.
NewStateCh chan connectivity.State // the last state.
ResolveNowCh chan resolver.ResolveNowOptions // the last ResolveNow().
subConnIdx int
}
// NewTestClientConn creates a TestClientConn.
func NewTestClientConn(t *testing.T) *TestClientConn {
return &TestClientConn{
logger: t,
NewSubConnAddrsCh: make(chan []resolver.Address, 10),
NewSubConnCh: make(chan balancer.SubConn, 10),
RemoveSubConnCh: make(chan balancer.SubConn, 10),
UpdateAddressesAddrsCh: make(chan []resolver.Address, 1),
NewPickerCh: make(chan balancer.Picker, 1),
NewStateCh: make(chan connectivity.State, 1),
ResolveNowCh: make(chan resolver.ResolveNowOptions, 1),
}
}
// NewSubConn creates a new SubConn.
func (tcc *TestClientConn) NewSubConn(a []resolver.Address, o balancer.NewSubConnOptions) (balancer.SubConn, error) {
sc := TestSubConns[tcc.subConnIdx]
tcc.subConnIdx++
tcc.logger.Logf("testClientConn: NewSubConn(%v, %+v) => %s", a, o, sc)
select {
case tcc.NewSubConnAddrsCh <- a:
default:
}
select {
case tcc.NewSubConnCh <- sc:
default:
}
return sc, nil
}
// RemoveSubConn removes the SubConn.
func (tcc *TestClientConn) RemoveSubConn(sc balancer.SubConn) {
tcc.logger.Logf("testClientConn: RemoveSubConn(%s)", sc)
select {
case tcc.RemoveSubConnCh <- sc:
default:
}
}
// UpdateAddresses updates the addresses on the SubConn.
func (tcc *TestClientConn) UpdateAddresses(sc balancer.SubConn, addrs []resolver.Address) {
tcc.logger.Logf("testClientConn: UpdateAddresses(%v, %+v)", sc, addrs)
select {
case tcc.UpdateAddressesAddrsCh <- addrs:
default:
}
}
// UpdateState updates connectivity state and picker.
func (tcc *TestClientConn) UpdateState(bs balancer.State) {
tcc.logger.Logf("testClientConn: UpdateState(%v)", bs)
select {
case <-tcc.NewStateCh:
default:
}
tcc.NewStateCh <- bs.ConnectivityState
select {
case <-tcc.NewPickerCh:
default:
}
tcc.NewPickerCh <- bs.Picker
}
// ResolveNow panics.
func (tcc *TestClientConn) ResolveNow(o resolver.ResolveNowOptions) {
select {
case <-tcc.ResolveNowCh:
default:
}
tcc.ResolveNowCh <- o
}
// Target panics.
func (tcc *TestClientConn) Target() string {
panic("not implemented")
}
// WaitForErrPicker waits until an error picker is pushed to this ClientConn.
// Returns error if the provided context expires or a non-error picker is pushed
// to the ClientConn.
func (tcc *TestClientConn) WaitForErrPicker(ctx context.Context) error {
select {
case <-ctx.Done():
return errors.New("timeout when waiting for an error picker")
case picker := <-tcc.NewPickerCh:
if _, perr := picker.Pick(balancer.PickInfo{}); perr == nil {
return fmt.Errorf("balancer returned a picker which is not an error picker")
}
}
return nil
}
// IsRoundRobin checks whether f's return value is roundrobin of elements from
// want. But it doesn't check for the order. Note that want can contain
// duplicate items, which makes it weight-round-robin.
//
// Step 1. the return values of f should form a permutation of all elements in
// want, but not necessary in the same order. E.g. if want is {a,a,b}, the check
// fails if f returns:
// - {a,a,a}: third a is returned before b
// - {a,b,b}: second b is returned before the second a
//
// If error is found in this step, the returned error contains only the first
// iteration until where it goes wrong.
//
// Step 2. the return values of f should be repetitions of the same permutation.
// E.g. if want is {a,a,b}, the check failes if f returns:
// - {a,b,a,b,a,a}: though it satisfies step 1, the second iteration is not
// repeating the first iteration.
//
// If error is found in this step, the returned error contains the first
// iteration + the second iteration until where it goes wrong.
func IsRoundRobin(want []balancer.SubConn, f func() balancer.SubConn) error {
wantSet := make(map[balancer.SubConn]int) // SubConn -> count, for weighted RR.
for _, sc := range want {
wantSet[sc]++
}
// The first iteration: makes sure f's return values form a permutation of
// elements in want.
//
// Also keep the returns values in a slice, so we can compare the order in
// the second iteration.
gotSliceFirstIteration := make([]balancer.SubConn, 0, len(want))
for range want {
got := f()
gotSliceFirstIteration = append(gotSliceFirstIteration, got)
wantSet[got]--
if wantSet[got] < 0 {
return fmt.Errorf("non-roundrobin want: %v, result: %v", want, gotSliceFirstIteration)
}
}
// The second iteration should repeat the first iteration.
var gotSliceSecondIteration []balancer.SubConn
for i := 0; i < 2; i++ {
for _, w := range gotSliceFirstIteration {
g := f()
gotSliceSecondIteration = append(gotSliceSecondIteration, g)
if w != g {
return fmt.Errorf("non-roundrobin, first iter: %v, second iter: %v", gotSliceFirstIteration, gotSliceSecondIteration)
}
}
}
return nil
}
// ErrTestConstPicker is error returned by test const picker.
var ErrTestConstPicker = fmt.Errorf("const picker error")
// TestConstPicker is a const picker for tests.
type TestConstPicker struct {
Err error
SC balancer.SubConn
}
// Pick returns the const SubConn or the error.
func (tcp *TestConstPicker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
if tcp.Err != nil {
return balancer.PickResult{}, tcp.Err
}
return balancer.PickResult{SubConn: tcp.SC}, nil
}