Server crashed after spamming it with many clients

[Seadragon91]

Description

Spammed the server with many clients using pycraft. The clients joined the server, disconnected and connected again in a loop.

Reproduction Steps

1. Spam the server with many clients and disconnect and reconnect them very quickly.

What You Expected to Happen

Server should be able to handle it, when many clients connects and disconnects.

What Actually Happened

Server crashes after spamming it with many clients.

Screenshots and Logs

thread main' panicked at 'called `Option::unwrap()` on a `None` value', feather/server/src/systems/view.rs:43:52

feather/feather/server/src/systems/view.rs

Line 43 in b63fd95

let client = server.clients.get(client_id).unwrap();

   0: rust_begin_unwind
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/std/src/panicking.rs:493:5
   1: core::panicking::panic_fmt
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/core/src/panicking.rs:50:5
   3: core::option::Option<T>::unwrap
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/core/src/option.rs:386:21
   4: feather_server::systems::view::send_new_chunks
             at /home/lukas/rust/feather/feather/server/src/systems/view.rs:43:22
   5: core::ops::function::FnMut::call_mut
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/core/src/ops/function.rs:150:5
   6: feather_ecs::system::GroupBuilder<Input,State>::make_function::{{closure}}
             at /home/lukas/rust/feather/feather/ecs/src/system.rs:193:13
   7: <alloc::boxed::Box<F,A> as core::ops::function::FnMut<Args>>::call_mut
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/alloc/src/boxed.rs:1335:9
   8: feather_ecs::system::SystemExecutor<Input>::run
             at /home/lukas/rust/feather/feather/ecs/src/system.rs:144:26
   9: feather_server::create_tick_loop::{{closure}}
             at /home/lukas/rust/feather/feather/server/src/main.rs:91:9
  10: <alloc::boxed::Box<F,A> as core::ops::function::FnMut<Args>>::call_mut
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/alloc/src/boxed.rs:1335:9
  11: feather_common::tick_loop::TickLoop::run
             at /home/lukas/rust/feather/feather/common/src/tick_loop.rs:25:31
  12: feather_server::run
             at /home/lukas/rust/feather/feather/server/src/main.rs:85:5
  13: feather_server::main::{{closure}}
             at /home/lukas/rust/feather/feather/server/src/main.rs:31:5
  14: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/core/src/future/mod.rs:80:19
  15: tokio::park::thread::CachedParkThread::block_on::{{closure}}
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.2.0/src/park/thread.rs:263:54
  16: tokio::coop::with_budget::{{closure}}
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.2.0/src/coop.rs:121:9
  17: std::thread::local::LocalKey<T>::try_with
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/std/src/thread/local.rs:272:16
  18: std::thread::local::LocalKey<T>::with
             at /rustc/cb75ad5db02783e8b0222fee363c5f63f7e2cf5b/library/std/src/thread/local.rs:248:9
  19: tokio::coop::with_budget
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.2.0/src/coop.rs:114:5
  20: tokio::coop::budget
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.2.0/src/coop.rs:98:5
  21: tokio::park::thread::CachedParkThread::block_on
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.2.0/src/park/thread.rs:263:31
  22: tokio::runtime::enter::Enter::block_on
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.2.0/src/runtime/enter.rs:151:13
  23: tokio::runtime::thread_pool::ThreadPool::block_on
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.2.0/src/runtime/thread_pool/mod.rs:71:9
  24: tokio::runtime::Runtime::block_on
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.2.0/src/runtime/mod.rs:452:43
  25: feather_server::main
             at /home/lukas/rust/feather/feather/server/src/main.rs:18:1

Your Environment

• Operating System: Debian
• Operating System Version: Debian GNU/Linux 10 (buster)
• Feather Version: On commit b63fd95

[DeusFerrariis]

Could you provide a repo with the pyCraft code used to produce this bug?

[oxkitsune]

Hey, thanks for the report! Did you compile in release mode? Also how many clients were connecting/reconnecting and what was the delay between these actions?

[Seadragon91]

The crash also occurs on release mode. I added a run file for pyCraft here:
https://github.com/Seadragon91/pyCraft/blob/feather/run_connect_reconnect.py.

I changed online_mode to false and changed max_players to 100. That are also how many clients are connecting and reconnecting.

[Seadragon91]

Was also able to reproduce it under windows in debug and release mode.

[Seadragon91]

Fixed by #440.