feat: add per-upstream concurrency limit via semaphore#25
Merged
cptrodgers merged 1 commit intomainfrom Mar 30, 2026
Merged
Conversation
cptrodgers
force-pushed
the
hn/max-upstream-connections
branch
from
e8d6d8f to
80ac137
Compare
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
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
Summary
tokio::sync::SemaphoretoAppStatethat caps concurrent upstream requests (default 100)forward_requestonly — released before response streaming, so it doesn't block SSE/long responsesmax_concurrent_upstreaminmcpr.tomlMotivation
Without a concurrency limit, slow upstream + high inbound traffic = unbounded tokio tasks holding request/response buffers → OOM. This adds natural backpressure: excess requests wait rather than accumulate.