Fix remote cache writes to not block the Pants run (Cherry-pick of #11947)#11950
Merged
Merged
Conversation
Closes pantsbuild#11908. As described there, `ensure_remote_has_recursive()` was blocking due to its call to `executor.block_on()`. This was introduced in pantsbuild#9793, which reasoned that only the spawned thread would get blocked, which would be safe - but it turns out that this blocking stops Pants from doing anything else. This was not introduced due to the upgrade from Tokio 0.2 to 1.x, and it's plausible this never worked as intended with remote caching, given that remote caching was not available in May 2020. Fundamentally, the issue makes sense. Reading from LMDB Store must be synchronous to be safe, which we correctly expressed, e.g. via using `Executor.spawn_blocking()`. We tried to minimize memory consumption by allowing for a callback to access a reference/slice of the bytes, rather than cloning it. However, we desire for the remote code to be async, e.g. so that it can finish in the background a la pantsbuild#11479. If it's async, it fundamentally would not be able to use a reference because that reference may no longer be valid - we need to clone the data to fully own it. While cloning the bytes will result in more memory consumption, it is imperative that remote caching fails gracefully. The increase in memory consumption is less offensive than pantsbuild#11908, i.e. that slowness in remote cache writes can slow down and even hang Pants. # Building wheels and fs_util will be skipped. Delete if not intended. [ci skip-build-wheels]
Contributor
Author
|
This was a clean cherry-pick. |
benjyw
approved these changes
Apr 21, 2021
Contributor
benjyw
left a comment
benjyw
left a comment
There was a problem hiding this comment.
Rubber-stamping, but I cannot verify the rust code. I assume this was a clean cherrypick.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
No description provided.