From c763c9b18df6ff0b77bed3ca839a720cd39ab2d6 Mon Sep 17 00:00:00 2001
From: Travis Bischel <travis.bischel+github@gmail.com>
Date: Sun, 20 Feb 2022 22:33:37 -0700
Subject: [PATCH] consuming: add NoResetOffset

This matches Kafka's "none" for the consume reset offset option: when
OffsetOutOfRange is encountered, the partition being consumed enters an
unrecoverable state.
---
 pkg/kgo/config.go   |  3 +++
 pkg/kgo/consumer.go | 21 +++++++++++++++++++++
 pkg/kgo/source.go   | 38 +++++++++++++++++++++++---------------
 3 files changed, 47 insertions(+), 15 deletions(-)

diff --git a/pkg/kgo/config.go b/pkg/kgo/config.go
index 24aec308..20389735 100644
--- a/pkg/kgo/config.go
+++ b/pkg/kgo/config.go
@@ -1177,6 +1177,9 @@ func MaxConcurrentFetches(n int) ConsumerOpt {
 // offset is before the partition's log start offset or after the high
 // watermark, this will reset to the start offset or end offset, respectively.
 // Relative offsets are only obeyed if they fall within bounds.
+//
+// You can use the NoResetOffset to change the behavior of the client to enter
+// a fatal state when OffsetOutOfRange is encountered.
 func ConsumeResetOffset(offset Offset) ConsumerOpt {
 	return consumerOpt{func(cfg *cfg) { cfg.resetOffset = offset }}
 }
diff --git a/pkg/kgo/consumer.go b/pkg/kgo/consumer.go
index 53994940..df3da14b 100644
--- a/pkg/kgo/consumer.go
+++ b/pkg/kgo/consumer.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math"
 	"sort"
 	"strings"
 	"sync"
@@ -52,6 +53,26 @@ func NewOffset() Offset {
 	}
 }
 
+var noResetOffset = Offset{
+	at:           math.MinInt64,
+	relative:     math.MinInt64,
+	epoch:        math.MinInt32,
+	currentEpoch: math.MinInt32,
+}
+
+// NoResetOffset returns an offset that can be used as a "none" option for the
+// ConsumeResetOffset option. The returned offset should not be modified; if it
+// is, it will no longer be the no reset offset.
+//
+// Using this offset will make it such that if OffsetOutOfRange is ever
+// encountered while consuming, rather than trying to recover, the client will
+// return the error to the user. Since the client does not record, the error
+// will forever be encountered and the partition is effectively in a fatal
+// state.
+func NoResetOffset() Offset {
+	return noResetOffset
+}
+
 // AtStart returns a copy of the calling offset, changing the returned offset
 // to begin at the beginning of a partition.
 func (o Offset) AtStart() Offset {
diff --git a/pkg/kgo/source.go b/pkg/kgo/source.go
index e7727194..8c2ebc7d 100644
--- a/pkg/kgo/source.go
+++ b/pkg/kgo/source.go
@@ -849,18 +849,29 @@ func (s *source) handleReqResp(br *broker, req *fetchRequest, resp *kmsg.FetchRe
 				// rare". Rather than falling back to listing offsets,
 				// we stay in a cycle of validating the leader epoch
 				// until the follower has caught up.
+				//
+				// In all cases except case 4, we also have to check if
+				// no reset offset was configured. If so, we ignore
+				// trying to reset and instead keep our failed partition.
+				addList := func(replica int32) {
+					if s.cl.cfg.resetOffset == noResetOffset {
+						keep = true
+					} else {
+						reloadOffsets.addLoad(topic, partition, loadTypeList, offsetLoad{
+							replica: replica,
+							Offset:  s.cl.cfg.resetOffset,
+						})
+					}
+				}
 
-				if s.nodeID == partOffset.from.leader { // non KIP-392 case
-					reloadOffsets.addLoad(topic, partition, loadTypeList, offsetLoad{
-						replica: -1,
-						Offset:  s.cl.cfg.resetOffset,
-					})
-				} else if partOffset.offset < fp.LogStartOffset { // KIP-392 case 3
-					reloadOffsets.addLoad(topic, partition, loadTypeList, offsetLoad{
-						replica: s.nodeID,
-						Offset:  s.cl.cfg.resetOffset,
-					})
-				} else { // partOffset.offset > fp.HighWatermark, KIP-392 case 4
+				switch {
+				case s.nodeID == partOffset.from.leader: // non KIP-392 case
+					addList(-1)
+
+				case partOffset.offset < fp.LogStartOffset: // KIP-392 case 3
+					addList(s.nodeID)
+
+				default: // partOffset.offset > fp.HighWatermark, KIP-392 case 4
 					if kip320 {
 						reloadOffsets.addLoad(topic, partition, loadTypeEpoch, offsetLoad{
 							replica: -1,
@@ -873,10 +884,7 @@ func (s *source) handleReqResp(br *broker, req *fetchRequest, resp *kmsg.FetchRe
 						// If the broker does not support offset for leader epoch but
 						// does support follower fetching for some reason, we have to
 						// fallback to listing.
-						reloadOffsets.addLoad(topic, partition, loadTypeList, offsetLoad{
-							replica: -1,
-							Offset:  s.cl.cfg.resetOffset,
-						})
+						addList(-1)
 					}
 				}