storage: fix index state truncate overflow

[andrwng]

Similar to #25979, when an index contains state that leads it to overflow, it is unreliable. In this case, this could affect truncation, and result in us removing incorrect index entries.

So, this makes the truncate avoid removing entries if this case is detected, with the expectation that no entries are added that have overflowed.

Note, this bug doesn't appear to be as severe as #25979 in that:

• suffix truncation is generally more rare
• the overflowing index problem is generally a problem with:
  • large segments, much larger than the default allowed size
  • compacted segments, which we expect to be relatively rare to suffix truncate with tiered storage

Nonetheless, some kind of fix seems appropriate because it's difficult to reason about the overflow otherwise.

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v25.1.x
• v24.3.x
• v24.2.x

Release Notes

• None

[andrwng]

Don't love the approach, open to alternative suggestions.

[bharathv]

lgtm .. not too familiar with this code but looks correct to me .. would prefer another pair of 👓

[vbotbuildovich]

CI test results

test results on build#65554

test_id	test_kind	job_url	test_status	passed
rptest.tests.basic_kafka_compat_test.TxKafkaCompatTest.test_concurrent_producer_ids.metadata_quorum=COMBINED_KRAFT	ducktape	https://buildkite.com/redpanda/redpanda/builds/65554#0196a26e-89da-4988-9dd6-7b6076b7f916	FLAKY	20/21
rptest.tests.partition_balancer_test.PartitionBalancerTest.test_rack_awareness	ducktape	https://buildkite.com/redpanda/redpanda/builds/65554#0196a26a-c285-45e4-b687-b45dc9f0a009	FAIL	0/1
rptest.tests.partition_move_interruption_test.PartitionMoveInterruption.test_cancelling_partition_move.replication_factor=3.unclean_abort=True.recovery=restart_recovery.compacted=False	ducktape	https://buildkite.com/redpanda/redpanda/builds/65554#0196a26e-89da-4988-9dd6-7b6076b7f916	FLAKY	20/21
rptest.tests.random_node_operations_test.RandomNodeOperationsTest.test_node_operations.enable_failures=True.mixed_versions=False.with_tiered_storage=False.with_iceberg=False.with_chunked_compaction=True.cloud_storage_type=CloudStorageType.S3	ducktape	https://buildkite.com/redpanda/redpanda/builds/65554#0196a26a-c285-45e4-b687-b45dc9f0a009	FLAKY	17/18
rptest.tests.scaling_up_test.ScalingUpTest.test_scaling_up_with_recovered_topic	ducktape	https://buildkite.com/redpanda/redpanda/builds/65554#0196a26a-c283-427f-8df0-c0afafc17b35	FLAKY	10/21

[dotnwat]

so we just skip removal and rely on queries to detect the overflow.

i'm not clear on what this means or how it works. the confusion i have is something like: if the truncation request is legit, but we ignore it because of the overflow, then how do we know that a later query would not be affected by having dropped a truncation request? presumably we rely on suffix truncation for raft correctness?

[andrwng]

The idea is that if entries aren't truncated here, it's because we are attempting to truncate to something beyond the uint32 delta limit. If that's the case:

• there should be no such entries in the index, and
• queries for beyond that limit should skip the binary search

Does that answer your question? Or are you getting at that there's still an edge case where a later query returns the wrong thing?

[dotnwat]

i think it looks ok. i'm less concerned about my question after read it again today

[vbotbuildovich]

/backport v25.1.x

[vbotbuildovich]

/backport v24.3.x

[vbotbuildovich]

/backport v24.2.x

[vbotbuildovich]

Failed to create a backport PR to v24.2.x branch. I tried:

git remote add upstream https://github.com/redpanda-data/redpanda.git
git fetch --all
git checkout -b backport-pr-26051-v24.2.x-295 remotes/upstream/v24.2.x
git cherry-pick -x e882d67ed6

Workflow run logs.

[vbotbuildovich]

Failed to create a backport PR to v25.1.x branch. I tried:

git remote add upstream https://github.com/redpanda-data/redpanda.git
git fetch --all
git checkout -b backport-pr-26051-v25.1.x-961 remotes/upstream/v25.1.x
git cherry-pick -x e882d67ed6

Workflow run logs.

[vbotbuildovich]

Failed to create a backport PR to v24.3.x branch. I tried:

git remote add upstream https://github.com/redpanda-data/redpanda.git
git fetch --all
git checkout -b backport-pr-26051-v24.3.x-196 remotes/upstream/v24.3.x
git cherry-pick -x e882d67ed6

Workflow run logs.