Frozen zellij session following input/output OS error 5

[espadrine]

Basic information

zellij --version: zellij 0.38.0
stty size: 273x75. Multiple sizes tried.
uname -av: Linux hs0 6.2.0-34-generic #34~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Thu Sep 7 13:12:03 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

Terminal emulators tried:

• alacritty 0.13.0-dev (33306142)
• konsole 23.08.2

Further information
Steps (hard to reproduce, as this seemed a bit probabilistic):

1. A program was running on a right pane, with five tabs including another one with another instance of the program running.
2. The program outputs ~2 lines per second, with bursts of ~400 lines every 5 seconds. It has been running for three days.
3. I very quickly scroll upward in the pane.
4. Zellij freezes, then the session closes with a message indicating that the session is not lost and that I can re-attach (which appears in the log printed below).
5. Doing zellij a or even zellij both freeze indefinitely, but indeed ps aux | grep zellij show it is still running, and the programs it contains still appear.

Related issue: same symptoms as #1588

/tmp/zellij-1000/zellij-log/zellij.log:

Caused by:
    0: failed to send message to client 1
    1: failed to send message to client 
ERROR  |???                      | 2023-11-08 21:28:20.030 [unnamed   ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-server-0.38.0/src/os_input_output.rs:385]: a non-fatal error occured

[Previous paragraph repeated many, many times.]

Caused by:
    0: failed to send message to client 1
    1: failed to send message to client 
ERROR  |???                      | 2023-11-08 21:28:20.030 [unnamed   ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-server-0.38.0/src/os_input_output.rs:385]: a non-fatal error occured

Caused by:
    0: failed to send message to client 1
    1: failed to send message to client 
ERROR  |???                      | 2023-11-09 03:09:13.650 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-client-0.38.0/src/lib.rs:472]: a non-fatal error occured

Caused by:
    0: failed to enable mouse mode
    1: Input/output error (os error 5) 
INFO   |zellij_client            | 2023-11-09 03:09:13.650 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-client-0.38.0/src/lib.rs:473]: Bye from Zellij! 
INFO   |zellij_client            | 2023-11-09 09:49:00.791 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-client-0.38.0/src/lib.rs:151]: Starting Zellij client! 
ERROR  |???                      | 2023-11-09 12:04:42.669 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-client-0.38.0/src/lib.rs:472]: a non-fatal error occured

Caused by:
    0: failed to enable mouse mode
    1: Input/output error (os error 5) 
INFO   |zellij_client            | 2023-11-09 12:04:42.669 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-client-0.38.0/src/lib.rs:473]: Bye from Zellij! 
INFO   |zellij_client            | 2023-11-09 16:13:37.251 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-client-0.38.0/src/lib.rs:151]: Starting Zellij client! 
WARN   |zellij_server::os_input_o| 2023-11-09 16:14:22.725 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-server-0.38.0/src/os_input_output.rs:407]: client 1 is processing server messages too slow 
ERROR  |???                      | 2023-11-09 16:14:22.725 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-server-0.38.0/src/lib.rs:484]: a non-fatal error occured

Caused by:
    0: failed to route server message to client 1
    1: failed to send message to client 1
    2: failed to send or buffer message for client 1
    3: sending on a full channel 
INFO   |zellij_client            | 2023-11-09 16:14:27.680 [main      ] [/home/tyl/.cargo/registry/src/index.crates.io-6f17d22bba15001f/zellij-client-0.38.0/src/lib.rs:473]: 
Your zellij client lost connection to the zellij server.

As a safety measure, you have been disconnected from the current zellij session.
However, the session should still exist and none of your data should be lost.

This usually means that your terminal didn't process server messages quick
enough. Maybe your system is currently under high load, or your terminal
isn't performant enough.

There are a few things you can try now:
    - Reattach to your previous session and see if it works out better this
      time: `zellij attach auspicious-pheasant`
    - Try using a faster (maybe GPU-accelerated) terminal emulator
     
(END)

[SecretPocketCat]

Getting a similar thing in foot (1.16.2) with the current zellij release (0.40.0) (built from main).
As described above, zellij freezes up and it's not possible to start a new client (or list sessions).

WARN   |zellij_server::os_input_o| 2024-04-19 00:18:38.919 [main      ] [zellij-server/src/os_input_output.rs:408]: client 2 is processing server messages too slow 
ERROR  |???                      | 2024-04-19 00:18:38.919 [main      ] [zellij-server/src/lib.rs:520]: a non-fatal error occured

Caused by:
    0: failed to route server message to client 2
    1: failed to send message to client 2
    2: failed to send or buffer message for client 2
    3: sending on a full channel

Stack backtrace:
   0: <unknown>
   1: <unknown>
   2: <unknown>
   3: <unknown>
   4: <unknown>
   5: __libc_start_main
   6: <unknown> 
ERROR  |zellij_utils::errors::not| 2024-04-19 00:19:10.316 [stdin_handler] [zellij-utils/src/errors.rs:652]: Panic occured:
             thread: stdin_handler
             location: At zellij-client/src/stdin_handler.rs:123:26
             message: called `Result::unwrap()` on an `Err` value: "SendError(..)" 

[imsnif]

Thanks for the reports and the logs everyone! This was a pretty tricky-to-reproduce edge case, but I got it in the linked PR. Will release a patch version with this and a few other fixes some time next week.