ConcurrencyException with Sitemaps when saving two content items at once

[Piedone]

Describe the bug

With the Sitemaps module enabled, you can get ConcurrencyException when saving two content items that are in the sitemaps simultaneously.

To Reproduce

1. Enable and configure the Sitemaps module.
2. Publish two content items at the same time. This needs a slower webserver/DB server, or you can simulate it by adding Thread.Sleep(5000); to SitemapManager.UpdateSitemapAsync().
3. Experience "ConcurrencyException: The document could not be updated as it has been changed by another process"

Expected behavior

Both publishes just work.

This is because ContentTypesSitemapUpdateHandler runs for every publish and updates the same single document. I guess the same issue can happen with simultaneous content item removals due to the same reason.

This can be fixed by putting sitemap updates in SitemapManager within a distributed lock, and instead of starting updates from a content handler, just adding a deferred task and doing the update there. So, updates would be synchronized without an adverse effect on the UX.

Screenshots

[MikeAlhayek]

@Piedone can you please submit a PR for this?

Too many 1.9 related issues that should be soon addressed.

[Piedone]

Yeah, I intend to work on this soon. Is this also a post-1.8 regression though?

[MikeAlhayek]

1.8 has been out for a while and I don't hear people screaming over it. We could back port it into 1.8 release branch and release 1.8.3 if needed.

I think once you submit a PR. We could release 1.8.3 if we end up not release 1.9 soonish

[Piedone]

Ah OK, just because you were asking about a PR in context of 1.9 issues.

But now it comes to me that this is definitely not a post-1.8 regression, since I have this with a client project on 1.7 (but the affected code is the same in main too).