From f0ebfc864d0588f39765c9c38e30aacb1dce7588 Mon Sep 17 00:00:00 2001
From: Plamen Bardarov <plamen.bardarov@sap.com>
Date: Mon, 4 Nov 2024 10:59:01 +0200
Subject: [PATCH] retry with backoff tests

---
 .../lib/common/common.go                      |  13 ++-
 .../lib/common/common_suite_test.go           |  13 +++
 .../lib/common/common_test.go                 | 110 ++++++++++++++++++
 3 files changed, 133 insertions(+), 3 deletions(-)
 create mode 100644 src/code.cloudfoundry.org/lib/common/common_suite_test.go
 create mode 100644 src/code.cloudfoundry.org/lib/common/common_test.go

diff --git a/src/code.cloudfoundry.org/lib/common/common.go b/src/code.cloudfoundry.org/lib/common/common.go
index 80d15280b..d36c0c154 100644
--- a/src/code.cloudfoundry.org/lib/common/common.go
+++ b/src/code.cloudfoundry.org/lib/common/common.go
@@ -3,11 +3,15 @@ package common
 import (
 	"code.cloudfoundry.org/lager/v3/lagerflags"
 	"fmt"
+	"github.com/pkg/errors"
 	"math"
-	"syscall"
 	"time"
 )
 
+type temporaryError interface {
+	Temporary() bool
+}
+
 type RetryableFunc[T any] func() (T, error)
 
 func GetLagerConfig() lagerflags.LagerConfig {
@@ -47,8 +51,11 @@ func RetryWithBackoff[T any](interval int, maxRetries int, fn RetryableFunc[T])
 }
 
 func isRetryableError(err error) bool {
-	if errno, ok := err.(syscall.Errno); ok {
-		return errno.Temporary()
+	var tempErr temporaryError
+
+	if errors.As(err, &tempErr) {
+		return tempErr.Temporary()
 	}
+
 	return false
 }
diff --git a/src/code.cloudfoundry.org/lib/common/common_suite_test.go b/src/code.cloudfoundry.org/lib/common/common_suite_test.go
new file mode 100644
index 000000000..087a1e585
--- /dev/null
+++ b/src/code.cloudfoundry.org/lib/common/common_suite_test.go
@@ -0,0 +1,13 @@
+package common_test
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+func TestCommon(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Common Suite")
+}
diff --git a/src/code.cloudfoundry.org/lib/common/common_test.go b/src/code.cloudfoundry.org/lib/common/common_test.go
new file mode 100644
index 000000000..024084437
--- /dev/null
+++ b/src/code.cloudfoundry.org/lib/common/common_test.go
@@ -0,0 +1,110 @@
+package common_test
+
+import (
+	"code.cloudfoundry.org/lib/common"
+	"fmt"
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	"time"
+)
+
+// Mock retryable error that implements temporaryError
+type mockTemporaryError struct {
+	msg string
+}
+
+func (e *mockTemporaryError) Error() string   { return e.msg }
+func (e *mockTemporaryError) Temporary() bool { return true }
+
+// Mock non-retryable error that does not implement temporaryError
+type mockNonRetryableError struct {
+	msg string
+}
+
+func (e *mockNonRetryableError) Error() string { return e.msg }
+
+var _ = Describe("Retry With Backoff", func() {
+	var (
+		callCount int
+	)
+
+	BeforeEach(func() {
+		callCount = 0
+	})
+
+	Context("when function succeeds the first try", func() {
+		It("returns result without retries", func() {
+			fn := func() (int, error) {
+				callCount++
+				return 42, nil
+			}
+
+			result, err := common.RetryWithBackoff(100, 3, fn)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(result).To(Equal(42))
+			Expect(callCount).To(Equal(1))
+		})
+	})
+
+	Context("when function fails with a non-retryable error", func() {
+		It("returns the error immediately", func() {
+			fn := func() (int, error) {
+				callCount++
+				return 0, &mockNonRetryableError{"non-retryable error"}
+			}
+
+			result, err := common.RetryWithBackoff(100, 3, fn)
+			Expect(err).To(MatchError("non-retryable error"))
+			Expect(result).To(Equal(0))
+			Expect(callCount).To(Equal(1))
+		})
+	})
+
+	Context("when function fails with a retryable error", func() {
+		It("retries the function up to maxRetries times and eventually succeeds", func() {
+			fn := func() (int, error) {
+				callCount++
+				if callCount == 3 {
+					return 42, nil
+				}
+				return 0, &mockTemporaryError{"retryable error"}
+			}
+
+			result, err := common.RetryWithBackoff(100, 3, fn)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(result).To(Equal(42))
+			Expect(callCount).To(Equal(3))
+		})
+	})
+
+	Context("when the maxRetries are exhausted", func() {
+		It("returns the last error", func() {
+			fn := func() (int, error) {
+				callCount++
+				return 0, &mockTemporaryError{fmt.Sprintf("retryable error %d", callCount)}
+			}
+
+			result, err := common.RetryWithBackoff(100, 3, fn)
+			Expect(err).To(MatchError(fmt.Sprintf("failed after 3 maxRetries: retryable error %d", 3)))
+			Expect(result).To(Equal(0))
+			Expect(callCount).To(Equal(3))
+		})
+	})
+
+	Context("exponential backoff timing", func() {
+		It("should do exponential backoff each retry", func() {
+			start := time.Now()
+
+			fn := func() (int, error) {
+				return 0, &mockTemporaryError{msg: "temporary error"}
+			}
+
+			common.RetryWithBackoff(50, 3, fn)
+			elapsed := time.Since(start)
+
+			// 50ms * (2^0 + 2^1 + 2^2) = 350ms
+			expectedTime := 350 * time.Millisecond
+			Expect(elapsed).To(BeNumerically(">=", expectedTime))
+		})
+	})
+})