nektos/act · error

--health-interval cannot be negative

Error message

--health-interval cannot be negative

What it means

Error [86]: After a successful ExecCreate, the ExecAttach API call (opening the hijacked stream to the exec) failed. The exec instance exists but act could not attach its stdin/stdout/stdout pipes. Usually a connection-level failure to the daemon or the exec expired/was cleaned up between create and attach.

Source

Thrown at pkg/container/docker_cli.go:586

	var healthConfig *container.HealthConfig
	haveHealthSettings := copts.healthCmd != "" ||
		copts.healthInterval != 0 ||
		copts.healthTimeout != 0 ||
		copts.healthStartPeriod != 0 ||
		copts.healthRetries != 0 ||
		copts.healthStartInterval != 0
	if copts.noHealthcheck {
		if haveHealthSettings {
			return nil, errors.New("--no-healthcheck conflicts with --health-* options")
		}
		healthConfig = &container.HealthConfig{Test: []string{"NONE"}}
	} else if haveHealthSettings {
		var probe []string
		if copts.healthCmd != "" {
			probe = []string{"CMD-SHELL", copts.healthCmd}
		}
		if copts.healthInterval < 0 {
			return nil, errors.New("--health-interval cannot be negative")
		}
		if copts.healthTimeout < 0 {
			return nil, errors.New("--health-timeout cannot be negative")
		}
		if copts.healthRetries < 0 {
			return nil, errors.New("--health-retries cannot be negative")
		}
		if copts.healthStartPeriod < 0 {
			return nil, errors.New("--health-start-period cannot be negative")
		}
		if copts.healthStartInterval < 0 {
			return nil, errors.New("--health-start-interval cannot be negative")
		}

		healthConfig = &container.HealthConfig{
			Test:          probe,
			Interval:      copts.healthInterval,
			Timeout:       copts.healthTimeout,

View on GitHub (pinned to 4f41128141)

Solutions

1. If DOCKER_HOST is remote, test stability: docker info repeatedly / switch to local socket
2. Reduce parallelism (act -j sequential) to lower daemon pressure
3. Restart Docker Desktop / dockerd if the socket is in a bad state, then re-run
4. Update Docker Engine; older daemons had attach race bugs

Example fix

# before: remote flaky socket
export DOCKER_HOST=tcp://flaky-host:2375
# after: local or reliable socket
unset DOCKER_HOST  # use /var/run/docker.sock

var lastErr error
for i := 0; i < 3; i++ {
	lastErr = run(ctx)
	if lastErr == nil || !strings.Contains(lastErr.Error(), "failed to attach to exec") {
		break
	}
	time.Sleep(time.Duration(i+1) * time.Second) // backoff, daemon may recover
}

When it happens

Trigger: cr.cli.ExecAttach erroring: daemon connection dropped (socket closed/TCP reset), exec instance removed before attach, or TTY mismatch with the daemon's expectations.

Common situations: DOCKER_HOST over tcp/ssh with flaky networking; Docker Desktop memory pressure restarting the daemon; heavy parallel execs timing out the attach window; VPN interfering with remote docker sockets.

Related errors

• --uts: invalid UTS mode
• --userns: invalid USER mode
• --health-timeout cannot be negative
• conflicting options: cannot specify both --ip6 and per-netwo
• conflicting options: cannot specify both --mac-address and p

AI-assisted analysis of nektos/act@4f41128141 (2026-08-15). Data as JSON: /api/errors/31060f84c3e75df4. Report an issue: GitHub.