compaction: formatted_sstables_list can potentially cause OOM

[vladzcloudius]

Installation details
HEAD: 780aee9

Description

formatted_sstables_list uses std::vector to store std::string objects what are sstables' names for a given compaction unit.

lass formatted_sstables_list {
    bool _include_origin = true;
    std::vector<std::string> _ssts;

With off-strategy compaction + repair thousands and even 100s of thousands sstables is not something impossible.

For 1000 entries the size of a linear vector buffer can become (assuming an sstable object size is 16B (pointer + size_t)) 16B*1000=16KB.

And even this not overly pessimistic case can create unnecessary pressure on seastar memory allocator.
Not to mention more extreme cases mentioned above.

It makes sense to use better suited container instead of std::vector here.
e.g. chunked_vector.

Found by a code review.

[mykaul]

#13907 probably missing 'Fixes' line, but I believe it fixes this issue and thus can be closed. @raphaelsc ?

[raphaelsc]

#13907 probably missing 'Fixes' line, but I believe it fixes this issue and thus can be closed. @raphaelsc ?

this is a secondary improvement suggested by Vlad, but the main problem observed was tracked by #14071 which is already closed by the fix

[vladzcloudius]

#13907 probably missing 'Fixes' line, but I believe it fixes this issue and thus can be closed. @raphaelsc ?

This GH issue was opened because I noticed this issue while reviewing #13907 (https://github.com/scylladb/scylladb/pull/13907/files#r1229971707)

So, no, #13907 does not resolve this issue.