From 1d31f50502715668abb90667f24a299c5e6ef407 Mon Sep 17 00:00:00 2001
From: Piotr Stachyra <piotr.stachyra@gmail.com>
Date: Mon, 11 Mar 2024 12:19:19 +0100
Subject: [PATCH] add exponential backoff when doing updates

---
 src/cassandra.go | 12 +++++++++++-
 src/operation.go | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 src/operation.go

diff --git a/src/cassandra.go b/src/cassandra.go
index 4aacbc8..c912ce9 100644
--- a/src/cassandra.go
+++ b/src/cassandra.go
@@ -157,7 +157,7 @@ func (kc *CassandraContext) selectRange(startTime, endTime time.Time) ([]Submiss
 	return submissions, nil
 }
 
-func (kc *CassandraContext) updateSubmissions(submissions []Submission) error {
+func (kc *CassandraContext) tryUpdateSubmissions(submissions []Submission) error {
 	// Define your dummy values here
 	dummyStateHash := "dummy_state_hash"
 	dummyParent := "dummy_parent"
@@ -182,6 +182,16 @@ func (kc *CassandraContext) updateSubmissions(submissions []Submission) error {
 	return nil
 }
 
+func (kc *CassandraContext) updateSubmissions(submissions []Submission) error {
+	return ExponentialBackoff(func() error {
+		if err := kc.tryUpdateSubmissions(submissions); err != nil {
+			kc.Log.Errorf("Error updating submissions (trying again): %v", err)
+			return err
+		}
+		return nil
+	}, maxRetries, initialBackoff)
+}
+
 // func (kc *CassandraContext) updateSubmissionsBatch(submissions []Submission) error {
 // 	batch := kc.Session.NewBatch(gocql.LoggedBatch) // Use gocql.UnloggedBatch for unlogged batches
 
diff --git a/src/operation.go b/src/operation.go
new file mode 100644
index 0000000..c0bf875
--- /dev/null
+++ b/src/operation.go
@@ -0,0 +1,34 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+// Operation is a function type that represents an operation that might fail and need a retry.
+type Operation func() error
+
+const (
+	maxRetries     = 5
+	initialBackoff = 300 * time.Millisecond
+)
+
+// ExponentialBackoff retries the provided operation with an exponential backoff strategy.
+func ExponentialBackoff(operation Operation, maxRetries int, initialBackoff time.Duration) error {
+	backoff := initialBackoff
+	var err error
+	for i := 0; i < maxRetries; i++ {
+		err = operation()
+		if err == nil {
+			return nil // Success
+		}
+
+		if i < maxRetries-1 {
+			// If not the last retry, wait for a bit
+			time.Sleep(backoff)
+			backoff *= 2 // Exponential increase
+		}
+	}
+
+	return fmt.Errorf("operation failed after %d retries, returned error: %s", maxRetries, err)
+}