From b464f31b389c9a7c45a5afe2b80b46f279ccf3a6 Mon Sep 17 00:00:00 2001
From: Jesper Hansen <hansen.jesper17@gmail.com>
Date: Wed, 10 Jul 2019 20:59:18 +0200
Subject: [PATCH] Add progressive backoff function (#11497)

* [MM-15267] Utils: add backoff function to allow retries (#10958)

* [MM-15267] Utils: add unit test and update retry logic (#10958)

* [MM-15267] Utils: Add three retries to ProgressiveRetry (#10958)

* [MM-15267] Utils: add comments for progressive retry (#10958)

* [MM-15267] Utils: add license header to newly added file (#10958)

* [MM-15267] Utils: fix typo (#10958)

* [MM-15267] Utils: inline callback in function call (#10958)

* [MM-15267] Utils: remove type definition for backoff callback function (#10958)

* [MM-15267] Utils: use lookup table for timeout duration (#10958)

* [MM-15267] Utils: table driven unit tests for Progressive Backoff (#10958)

* [MM-15267] Utils: simplify retry function (#10958)

* [MM-15267] Utils: add assert and require packages to test file (#10958)

* [MM-15267] Utils: revert changes in go.mod and go.sum (#10958)
---
 plugin/helpers_bots.go | 18 ++++++++----
 utils/backoff.go       | 26 ++++++++++++++++++
 utils/backoff_test.go  | 62 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 101 insertions(+), 5 deletions(-)
 create mode 100644 utils/backoff.go
 create mode 100644 utils/backoff_test.go

diff --git a/plugin/helpers_bots.go b/plugin/helpers_bots.go
index 664a954d5d..28ed4df3f0 100644
--- a/plugin/helpers_bots.go
+++ b/plugin/helpers_bots.go
@@ -4,9 +4,8 @@
 package plugin
 
 import (
-	"time"
-
 	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/utils"
 	"github.com/pkg/errors"
 )
 
@@ -17,11 +16,20 @@ func (p *HelpersImpl) EnsureBot(bot *model.Bot) (retBotId string, retErr error)
 	}
 
 	// If we fail for any reason, this could be a race between creation of bot and
-	// retreval from anouther EnsureBot. Just try the basic retrieve existing again.
+	// retrieval from another EnsureBot. Just try the basic retrieve existing again.
 	defer func() {
 		if retBotId == "" || retErr != nil {
-			time.Sleep(time.Second)
-			botIdBytes, err := p.API.KVGet(BOT_USER_KEY)
+			var err error
+			var botIdBytes []byte
+
+			err = utils.ProgressiveRetry(func() error {
+				botIdBytes, err = p.API.KVGet(BOT_USER_KEY)
+				if err != nil {
+					return err
+				}
+				return nil
+			})
+
 			if err == nil && botIdBytes != nil {
 				retBotId = string(botIdBytes)
 				retErr = nil
diff --git a/utils/backoff.go b/utils/backoff.go
new file mode 100644
index 0000000000..be6dcc9a79
--- /dev/null
+++ b/utils/backoff.go
@@ -0,0 +1,26 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package utils
+
+import (
+	"time"
+)
+
+var backoffTimeouts = []time.Duration{50 * time.Millisecond, 100 * time.Millisecond, 200 * time.Millisecond, 200 * time.Millisecond, 400 * time.Millisecond, 400 * time.Millisecond}
+
+// ProgressiveRetry executes a BackoffOperation and waits an increasing time before retrying the operation.
+func ProgressiveRetry(operation func() error) error {
+	var err error
+
+	for attempts := 0; attempts < len(backoffTimeouts); attempts++ {
+		err = operation()
+		if err == nil {
+			return nil
+		}
+
+		time.Sleep(backoffTimeouts[attempts])
+	}
+
+	return err
+}
diff --git a/utils/backoff_test.go b/utils/backoff_test.go
new file mode 100644
index 0000000000..1ebff82e73
--- /dev/null
+++ b/utils/backoff_test.go
@@ -0,0 +1,62 @@
+package utils
+
+import (
+	"testing"
+
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestProgressiveRetry(t *testing.T) {
+	var retries int
+
+	type args struct {
+		operation func() error
+	}
+	tests := []struct {
+		name            string
+		args            args
+		wantErr         bool
+		expectedRetries int
+	}{
+		{
+			name: "Should fail and return error",
+			args: args{
+				operation: func() error {
+					retries++
+					return errors.New("Operation Failed")
+				},
+			},
+			wantErr:         true,
+			expectedRetries: 6,
+		},
+		{
+			name: "Should succeed after two retries",
+			args: args{
+				operation: func() error {
+					retries++
+					if retries == 2 {
+						return nil
+					}
+
+					return errors.New("Operation Failed")
+				},
+			},
+			wantErr:         false,
+			expectedRetries: 2,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			retries = 0
+
+			err := ProgressiveRetry(tt.args.operation)
+			if !tt.wantErr {
+				require.Nil(t, err)
+			}
+
+			assert.Equal(t, tt.expectedRetries, retries)
+		})
+	}
+}