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storage: return one entry less in Entries #29579

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merged 1 commit into from
Sep 6, 2018

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@tbg tbg commented Sep 5, 2018

This works around the bug outlined in:

etcd-io/etcd#10063

by matching Raft's internal implementation of commit pagination.
Once the above PR lands, we can revert this commit (but I assume
that it will take a little bit), and I think we should do that
because the code hasn't gotten any nicer to look at.

Fixes #28918.

Release note: None

@tbg tbg requested a review from a team September 5, 2018 11:11
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:lgtm: though this is worth having another pair of eyes scrutinize it. @nvanbenschoten?

Reviewable status: :shipit: complete! 0 of 0 LGTMs obtained (and 1 stale)


pkg/storage/entry_cache.go, line 196 at r1 (raw file):

		ent := v.(*raftpb.Entry)
		size := uint64(ent.Size())
		if maxBytes > 0 && bytes+size > maxBytes {

Did you consider an alternative approach to add a truncateEntries() function which takes a slice of entries, lo and hi indexes and a maxSize setting and duplicates the etcd/raft semantics? That seems like it would avoid a change here and could be more easily tested.

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Reviewed 5 of 6 files at r1.
Reviewable status: :shipit: complete! 1 of 0 LGTMs obtained


pkg/storage/entry_cache.go, line 181 at r1 (raw file):

func (rec *raftEntryCache) getEntries(
	ents []raftpb.Entry, rangeID roachpb.RangeID, lo, hi, maxBytes uint64,
) (_ []raftpb.Entry, size uint64, nextIndex uint64, hitMaxSize bool) {

s/hitMaxSize/exceededMaxBytes/


pkg/storage/entry_cache.go, line 196 at r1 (raw file):

Previously, petermattis (Peter Mattis) wrote…

Did you consider an alternative approach to add a truncateEntries() function which takes a slice of entries, lo and hi indexes and a maxSize setting and duplicates the etcd/raft semantics? That seems like it would avoid a change here and could be more easily tested.

If we did that, we'd need to make sure we call it twice so that we can short-circuit before hitting RocksDB in the happy-path. If we're doing that then it doesn't seem to buy us much.


pkg/storage/replica_raftstorage.go, line 162 at r1 (raw file):

		// Note that we track the size of proposals with payloads inlined.
		size += uint64(ent.Size())
		if maxBytes > 0 && size > maxBytes {

What does it mean for maxBytes == 0? I thought Raft uses math.MaxUint64 when it doesn't want a limit.

This works around the bug outlined in:

etcd-io/etcd#10063

by matching Raft's internal implementation of commit pagination.
Once the above PR lands, we can revert this commit (but I assume
that it will take a little bit), and I think we should do that
because the code hasn't gotten any nicer to look at.

Fixes cockroachdb#28918.

Release note: None
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Reviewable status: :shipit: complete! 0 of 0 LGTMs obtained (and 1 stale)


pkg/storage/entry_cache.go, line 181 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

s/hitMaxSize/exceededMaxBytes/

Done.


pkg/storage/entry_cache.go, line 196 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

If we did that, we'd need to make sure we call it twice so that we can short-circuit before hitting RocksDB in the happy-path. If we're doing that then it doesn't seem to buy us much.

I did consider it, but as Nathan pointed out it didn't look any better.


pkg/storage/replica_raftstorage.go, line 162 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

What does it mean for maxBytes == 0? I thought Raft uses math.MaxUint64 when it doesn't want a limit.

I think this was just crufty. Removed.

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Reviewable status: :shipit: complete! 0 of 0 LGTMs obtained (and 1 stale)


pkg/storage/entry_cache.go, line 196 at r1 (raw file):

Previously, tschottdorf (Tobias Schottdorf) wrote…

I did consider it, but as Nathan pointed out it didn't look any better.

Right, we'd have to call it twice, but we'd ensure that the same logic is used in both places and could test it in isolation. I don't feel strongly about this and you're already testing both logic paths, so carry on.

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tbg commented Sep 6, 2018

bors r=petermattis

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craig bot commented Sep 6, 2018

Build failed (retrying...)

craig bot pushed a commit that referenced this pull request Sep 6, 2018
29579: storage: return one entry less in Entries r=petermattis a=tschottdorf

This works around the bug outlined in:

etcd-io/etcd#10063

by matching Raft's internal implementation of commit pagination.
Once the above PR lands, we can revert this commit (but I assume
that it will take a little bit), and I think we should do that
because the code hasn't gotten any nicer to look at.

Fixes #28918.

Release note: None

29631: cli: handle merged range descriptors in debug keys r=petermattis a=tschottdorf

Noticed during #29252.

Release note: None

Co-authored-by: Tobias Schottdorf <tobias.schottdorf@gmail.com>
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:lgtm:

Reviewable status: :shipit: complete! 0 of 0 LGTMs obtained (and 2 stale)

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craig bot commented Sep 6, 2018

Build succeeded

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4 participants