Merge branch 'retryupdate' into 'master'

retryupdate task

See merge request slon/shad-go-private!13

go.mod

@@ -4,6 +4,8 @@ go 1.13
 
 require (
 	github.com/go-resty/resty/v2 v2.1.0
+	github.com/gofrs/uuid v3.2.0+incompatible
+	github.com/golang/mock v1.4.1
 	github.com/spf13/cobra v0.0.5
 	github.com/stretchr/testify v1.4.0
 	go.uber.org/goleak v1.0.0

go.sum

@@ -15,6 +15,10 @@ github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMo
 github.com/go-resty/resty/v2 v2.1.0 h1:Z6IefCpUMfnvItVJaJXWv/pMiiD11So35QgwEELsldE=
 github.com/go-resty/resty/v2 v2.1.0/go.mod h1:dZGr0i9PLlaaTD4H/hoZIDjQ+r6xq8mgbRzHZf7f2J8=
 github.com/go-sql-driver/mysql v1.4.1/go.mod h1:zAC/RDZ24gD3HViQzih4MyKcchzm+sOG5ZlKdlhCg5w=
+github.com/gofrs/uuid v3.2.0+incompatible h1:y12jRkkFxsd7GpqdSZ+/KCs/fJbqpEXSGd4+jfEaewE=
+github.com/gofrs/uuid v3.2.0+incompatible/go.mod h1:b2aQJv3Z4Fp6yNu3cdSllBxTCLRxnplIgP/c0N/04lM=
+github.com/golang/mock v1.4.1 h1:ocYkMQY5RrXTYgXl7ICpV0IXwlEQGwKIsery4gyXa1U=
+github.com/golang/mock v1.4.1/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt3cw=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/gonum/blas v0.0.0-20181208220705-f22b278b28ac/go.mod h1:P32wAyui1PQ58Oce/KYkOqQv8cVw1zAapXOl+dRFGbc=
 github.com/gonum/floats v0.0.0-20181209220543-c233463c7e82/go.mod h1:PxC8OnwL11+aosOB5+iEPoV3picfs8tUpkVd0pDo+Kg=
@@ -77,8 +81,10 @@ golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sys v0.0.0-20181205085412-a5c9d58dba9a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
+golang.org/x/tools v0.0.0-20190425150028-36563e24a262/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
 golang.org/x/tools v0.0.0-20191108193012-7d206e10da11/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20200125223703-d33eef8e6825 h1:aNQeSIHKi0RWpKA5NO0CqyLjx6Beh5l0LLUEnndEjz0=
 golang.org/x/tools v0.0.0-20200125223703-d33eef8e6825/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
@@ -96,3 +102,5 @@ gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8 h1:obN1ZagJSUGI0Ek/LBmuj4SNLPfIny3KsKFopxRdj10=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+rsc.io/quote/v3 v3.1.0/go.mod h1:yEA65RcK8LyAZtP9Kv3t0HmxON59tX3rD+tICJqUlj0=
+rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=

retryupdate/README.md

@@ -0,0 +1,30 @@
+# retryupdate
+
+В этой задаче, вам нужно познакомиться с паттернами обработки ошибок в golang.
+
+Вам дан клиент вымышленного сервиса. Сервис хранит отображение `key -> (value, version)`,
+где `key` и `value` - это обычные строки. А `version` - уникальный идентификатор, который сгенерировал
+клиент.
+
+Вам доступны два метода - `Get` и `Set`. Поведение методов описано в пакете `kvapi`.
+
+Методы могут завершаться с различными ошибками. Ошибки описаны в том же пакете.
+
+Вам нужно реализовать функцию `UpdateValue`, которая принимает ключ и функцию
+для "обновления" значения. Функция должна обновить значение по ключу, правильно обрабатывая
+ошибки, возникающие в процессе работы.
+
+ - Если ключ не нашёлся, нужно передать в `updateFn` значение `nil`.
+ - Если произошла ошибка доступа, то нужно сразу выходить.
+ - Если произошла ошибка внутри updateFn, то нужно сразу выходить.
+ - Если случился конфликт при записи, и значение изменилось с момента последнего чтения,
+   то нужно прочитать новое значение и попробовать заново.
+ - Любые другие ошибки из `api` нужно "ретраить" бесконечно.
+
+Функция должна минимизировать число запросов к API.
+
+Для генерации нового `uuid` на клиенте, используйте вызов `uuid.Must(uuid.NewV4())`.
+
+Большую цепочку `if`-ов удобнее писать через `switch`.
+
+Для выхода из вложенных циклов вам помогут [loop labels](https://golang.org/doc/effective_go.html#switch).

retryupdate/kvapi/api.go

@@ -0,0 +1,36 @@
+// +build !change
+
+package kvapi
+
+import "github.com/gofrs/uuid"
+
+type (
+	Client interface {
+		// Get the value of key.
+		Get(req *GetRequest) (*GetResponse, error)
+
+		// Set key to hold given value.
+		Set(rsp *SetRequest) (*SetResponse, error)
+	}
+
+	GetRequest struct {
+		Key string
+	}
+
+	GetResponse struct {
+		Value   string
+		Version uuid.UUID
+	}
+
+	SetRequest struct {
+		Key, Value string
+
+		// OldVersion field is checked before updating value.
+		//
+		// When updating old value, OldVersion must specify uuid of currently stored value.
+		// When creating new value, OldVersion must hold zero value of UUID.
+		OldVersion, NewVersion uuid.UUID
+	}
+
+	SetResponse struct{}
+)

retryupdate/kvapi/errors.go

@@ -0,0 +1,50 @@
+// +build !change
+
+package kvapi
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/gofrs/uuid"
+)
+
+var (
+	_ error = (*APIError)(nil)
+	_ error = (*ConflictError)(nil)
+	_ error = (*AuthError)(nil)
+)
+
+var ErrKeyNotFound = errors.New("key not found")
+
+type (
+	APIError struct {
+		Method string
+
+		Err error
+	}
+
+	ConflictError struct {
+		ProvidedVersion, ExpectedVersion uuid.UUID
+	}
+
+	AuthError struct {
+		Msg string
+	}
+)
+
+func (a *APIError) Error() string {
+	return fmt.Sprintf("api: %q error: %v", a.Method, a.Err)
+}
+
+func (a *APIError) Unwrap() error {
+	return a.Err
+}
+
+func (a *ConflictError) Error() string {
+	return fmt.Sprintf("api: conflict: expected_version=%d, provided_version=%d", a.ExpectedVersion, a.ProvidedVersion)
+}
+
+func (a *AuthError) Error() string {
+	return fmt.Sprintf("api: auth: %s", a.Msg)
+}

retryupdate/mock_test.go

@@ -0,0 +1,64 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: gitlab.com/slon/shad-go/retryupdate/kvapi (interfaces: Client)
+
+// Package retryupdate_test is a generated GoMock package.
+package retryupdate_test
+
+import (
+	gomock "github.com/golang/mock/gomock"
+	kvapi "gitlab.com/slon/shad-go/retryupdate/kvapi"
+	reflect "reflect"
+)
+
+// MockClient is a mock of Client interface
+type MockClient struct {
+	ctrl     *gomock.Controller
+	recorder *MockClientMockRecorder
+}
+
+// MockClientMockRecorder is the mock recorder for MockClient
+type MockClientMockRecorder struct {
+	mock *MockClient
+}
+
+// NewMockClient creates a new mock instance
+func NewMockClient(ctrl *gomock.Controller) *MockClient {
+	mock := &MockClient{ctrl: ctrl}
+	mock.recorder = &MockClientMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use
+func (m *MockClient) EXPECT() *MockClientMockRecorder {
+	return m.recorder
+}
+
+// Get mocks base method
+func (m *MockClient) Get(arg0 *kvapi.GetRequest) (*kvapi.GetResponse, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Get", arg0)
+	ret0, _ := ret[0].(*kvapi.GetResponse)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Get indicates an expected call of Get
+func (mr *MockClientMockRecorder) Get(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Get", reflect.TypeOf((*MockClient)(nil).Get), arg0)
+}
+
+// Set mocks base method
+func (m *MockClient) Set(arg0 *kvapi.SetRequest) (*kvapi.SetResponse, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Set", arg0)
+	ret0, _ := ret[0].(*kvapi.SetResponse)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Set indicates an expected call of Set
+func (mr *MockClientMockRecorder) Set(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Set", reflect.TypeOf((*MockClient)(nil).Set), arg0)
+}

retryupdate/update.go

@@ -0,0 +1,9 @@
+// +build !solution
+
+package retryupdate
+
+import "gitlab.com/slon/shad-go/retryupdate/kvapi"
+
+func UpdateValue(c kvapi.Client, key string, updateFn func(oldValue *string) (newValue string, err error)) error {
+	panic("implement me")
+}

retryupdate/update_test.go

@@ -0,0 +1,303 @@
+package retryupdate_test
+
+//go:generate mockgen -destination mock_test.go -package retryupdate_test gitlab.com/slon/shad-go/retryupdate/kvapi Client
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/gofrs/uuid"
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/require"
+
+	"gitlab.com/slon/shad-go/retryupdate"
+	"gitlab.com/slon/shad-go/retryupdate/kvapi"
+)
+
+var (
+	K0 = "K0"
+	V0 = "V0"
+	V1 = "V1"
+	V2 = "V2"
+	V3 = "V3"
+
+	UUID0 = uuid.Must(uuid.NewV4())
+	UUID1 = uuid.Must(uuid.NewV4())
+	UUID2 = uuid.Must(uuid.NewV4())
+
+	errUpdate = errors.New("update error")
+
+	errGetAuth = &kvapi.APIError{Method: "get", Err: &kvapi.AuthError{Msg: "token expired"}}
+	errSetAuth = &kvapi.APIError{Method: "set", Err: &kvapi.AuthError{Msg: "token expired"}}
+
+	errGetNoKey = &kvapi.APIError{Method: "get", Err: kvapi.ErrKeyNotFound}
+	errSetNoKey = &kvapi.APIError{Method: "set", Err: kvapi.ErrKeyNotFound}
+
+	errGetTemporary = &kvapi.APIError{Method: "get", Err: errors.New("unavailable")}
+	errSetTemporary = &kvapi.APIError{Method: "set", Err: errors.New("unavailable")}
+)
+
+type setMatcher struct {
+	kvapi.SetRequest
+
+	save *uuid.UUID
+}
+
+func (m setMatcher) Matches(x interface{}) bool {
+	if arg, ok := x.(*kvapi.SetRequest); ok {
+		if m.save != nil {
+			*m.save = arg.NewVersion
+		}
+
+		return arg.Key == m.Key && arg.Value == m.Value && arg.OldVersion == m.OldVersion
+	}
+
+	return false
+}
+
+func (m setMatcher) String() string {
+	return fmt.Sprintf("%v", m.SetRequest)
+}
+
+func SetRequest(k, v string, oldVersion uuid.UUID, saveUUID ...*uuid.UUID) gomock.Matcher {
+	m := setMatcher{
+		SetRequest: kvapi.SetRequest{
+			Key:        k,
+			Value:      v,
+			OldVersion: oldVersion,
+		},
+	}
+
+	if len(saveUUID) > 1 {
+		panic("error")
+	}
+
+	if len(saveUUID) == 1 {
+		m.save = saveUUID[0]
+	}
+
+	return m
+}
+
+func updateFn(oldValue *string) (string, error) {
+	switch {
+	case oldValue == nil:
+		return V0, nil
+	case *oldValue == V0:
+		return V1, nil
+	case *oldValue == V1:
+		return V2, nil
+	case *oldValue == V2:
+		return V3, nil
+	default:
+		return "", errUpdate
+	}
+}
+
+func TestSimpleUpdate(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(&kvapi.GetResponse{Value: V0, Version: UUID0}, nil),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V1, UUID0)).
+			Return(&kvapi.SetResponse{}, nil),
+	)
+
+	require.NoError(t, retryupdate.UpdateValue(c, K0, updateFn))
+}
+
+func TestUpdateFnError(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(&kvapi.GetResponse{Value: V3, Version: UUID0}, nil),
+	)
+
+	require.Equal(t, errUpdate, retryupdate.UpdateValue(c, K0, updateFn))
+}
+func TestCreateKey(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(nil, errGetNoKey),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V0, uuid.UUID{})).
+			Return(&kvapi.SetResponse{}, nil),
+	)
+
+	require.NoError(t, retryupdate.UpdateValue(c, K0, updateFn))
+}
+
+func TestKeyVanished(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(&kvapi.GetResponse{Value: V2, Version: UUID0}, nil),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V3, UUID0)).
+			Return(nil, errSetNoKey),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V0, uuid.UUID{})).
+			Return(&kvapi.SetResponse{}, nil),
+	)
+
+	require.NoError(t, retryupdate.UpdateValue(c, K0, updateFn))
+}
+
+func TestFailOnAuthErrorInGet(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(nil, errGetAuth),
+	)
+
+	require.Equal(t, errGetAuth, retryupdate.UpdateValue(c, K0, updateFn))
+}
+
+func TestFailOnAuthErrorInSet(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(nil, errGetNoKey),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V0, uuid.UUID{})).
+			Return(nil, errSetAuth),
+	)
+
+	require.Equal(t, errSetAuth, retryupdate.UpdateValue(c, K0, updateFn))
+}
+
+func TestRetryGetError(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(nil, errGetTemporary),
+
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(nil, errGetTemporary),
+
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(&kvapi.GetResponse{Value: V0, Version: UUID0}, nil),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V1, UUID0)).
+			Return(&kvapi.SetResponse{}, nil),
+	)
+
+	require.NoError(t, retryupdate.UpdateValue(c, K0, updateFn))
+}
+
+func TestRetrySetError(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(&kvapi.GetResponse{Value: V0, Version: UUID0}, nil),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V1, UUID0)).
+			Return(nil, errSetTemporary),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V1, UUID0)).
+			Return(&kvapi.SetResponse{}, nil),
+	)
+
+	require.NoError(t, retryupdate.UpdateValue(c, K0, updateFn))
+}
+
+func TestRetrySetConflict(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(&kvapi.GetResponse{Value: V0, Version: UUID0}, nil),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V1, UUID0)).
+			Return(nil, errSetTemporary),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V1, UUID0)).
+			Return(nil, &kvapi.APIError{Method: "set", Err: &kvapi.ConflictError{ExpectedVersion: UUID1, ProvidedVersion: UUID0}}),
+
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(&kvapi.GetResponse{Value: V2, Version: UUID1}, nil),
+
+		c.EXPECT().
+			Set(SetRequest(K0, V3, UUID1)).
+			Return(&kvapi.SetResponse{}, nil),
+	)
+
+	require.NoError(t, retryupdate.UpdateValue(c, K0, updateFn))
+}
+
+func TestRetrySetFalseConflict(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	conflictErr := &kvapi.ConflictError{ProvidedVersion: UUID0}
+
+	c := NewMockClient(ctrl)
+	gomock.InOrder(
+		c.EXPECT().
+			Get(&kvapi.GetRequest{Key: K0}).
+			Return(&kvapi.GetResponse{Value: V0, Version: UUID0}, nil),
+
+		// first Set updates key state, but returns an error.
+		c.EXPECT().
+			Set(SetRequest(K0, V1, UUID0, &conflictErr.ExpectedVersion)).
+			Return(nil, errSetTemporary),
+
+		// second Set returns conflict with ExpectedVersion == OldVersion from previous request.
+		c.EXPECT().
+			Set(SetRequest(K0, V1, UUID0)).
+			Return(nil, &kvapi.APIError{Method: "set", Err: conflictErr}),
+	)
+
+	require.NoError(t, retryupdate.UpdateValue(c, K0, updateFn))
+}