superfly/corrosion

Subscription channel can run out of capacity and drop events

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#183 opened on Apr 11, 2024

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 (2 comments) (0 reactions) (0 assignees)Rust (83 forks)auto 404
buggood first issuehelp wanted

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Description

The broadcast channel used by subscriptions (https://github.com/superfly/corrosion/blob/93561d180e3ebbdd275c9b80b9663b6dcb46e2fa/crates/corro-agent/src/api/public/pubsub.rs#L621) can run out of capacity and skip the events in case the data is read really fast from the disk.

Somehow, in this case, forward_sub_to_sender simply stops forwarding any event - https://github.com/superfly/corrosion/blob/93561d180e3ebbdd275c9b80b9663b6dcb46e2fa/crates/corro-agent/src/api/public/pubsub.rs#L728

It looks like the select! never matches RecvError::Lagged for some reasons.

Contributor guide

Research direction
Investigate the broadcast channel used for subscriptions and the forward sub to sender function. Understand why the select! loop might not receive RecvError::Lagged when the channel overflows. Check the channel capacity and how events are produced and consumed. Look for related tests or run a local reproduction.
Tech stack
rust
Domain
backenddistributed systems
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitRustAsync programming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40