[CI] TestComposeExec test is flaky

[swagatbora90]

Description

CI failed in a recent PR test run #4378

Steps to reproduce the issue

https://github.com/containerd/nerdctl/actions/runs/15914386443/job/44889234700?pr=4378

Describe the results you received and expected

=== CONT  TestComposeExec/exec_no_tty
    compose_exec_linux_test.go:174: 
        
        +============================================================================================================+
        | 🚀      | "TestComposeExec/exec_no_tty": starting test!                                                    |
        +============================================================================================================+
        | ⏳      | /tmp/TestComposeExecexec_no_tty1780160761/001/aba848d0                                           |
        +============================================================================================================+
        |         |                                                                                                  |
        +============================================================================================================+
        | config  | {                                                                                                |
        |         |   "Namespace": "nerdctl-test",                                                                   |
        |         |   "PrivateMode": ""                                                                              |
        |         | }                                                                                                |
        +============================================================================================================+
        | labels  | {}                                                                                               |
        +============================================================================================================+
        
    compose_exec_linux_test.go:174: 
        
        +------------------------------------------------------------------------------------------------------------+
        | ➡️      | ⚙️ /usr/local/bin/nerdctl compose -f /tmp/TestComposeExec2091485524/001/dca1da9c/compose.yaml ex |
        |         | ec -i=false --no-TTY svc0 echo success                                                           |
        +------------------------------------------------------------------------------------------------------------+
        | 🌱      | XDG_SESSION_TYPE=tty                                                                             |
        |         | HOME=/home/rootless                                                                              |
        |         | XDG_SESSION_CLASS=user                                                                           |
        |         | XDG_SESSION_ID=3                                                                                 |
        |         | XDG_RUNTIME_DIR=/run/user/1001                                                                   |
        |         | PATH=/usr/local/go/bin:/usr/local/go/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin |
        |         | :/bin:/usr/games:/usr/local/games:/snap/bin                                                      |
        |         | DOCKER_CONFIG=/tmp/TestComposeExecexec_no_tty1780160761/003                                      |
        |         | NERDCTL_TOML=/tmp/TestComposeExecexec_no_tty1780160761/003/nerdctl.toml                          |
        +------------------------------------------------------------------------------------------------------------+
        | ⏰      | <1s (limit: 3m0s)                                                                                |
        +------------------------------------------------------------------------------------------------------------+
        | 📁      | /tmp/TestComposeExecexec_no_tty1780160761/002                                                    |
        +------------------------------------------------------------------------------------------------------------+
        
    compose_exec_linux_test.go:174: 	
        
        <<<<<<<<<<<<<<<<<<<<
        	🖊️ Inspecting output (equals)
        	👀 testing:		``
        	❌ FAILED!		= `success
        `
        >>>>>>>>>>>>>>>>>>>>
        
--- FAIL: TestComposeExec/exec_no_tty (0.18s)

What version of nerdctl are you using?

Mainline

Are you using a variant of nerdctl? (e.g., Rancher Desktop)

None

Host information

No response

[AkihiroSuda]

Is this failure specific to rootless?

[swagatbora90]

This does not appear to be rootless specific but some race in capturing task io. Can this be due to compose exec command exiting even before the task could output to its io stream? Fwiw I am not able to reproduce this locally.

[apostasie]

This does not appear to be rootless specific but some race in capturing task io. Can this be due to compose exec command exiting even before the task could output to its io stream? Fwiw I am not able to reproduce this locally.

Could be.
We do have similar issues with logs, healthcheck.
#4383 might be fixing it for healthcheck.

We should have a look at what we are doing with task IO overall.