[CI/Build] Clean up timed-out K8s E2E runs and fail fast on backend exits

[lfsun02]

Summary

In several recent PRs, a timed-out K8s E2E test could leave GPU pods running, causing the subsequent static-discovery job to fail due to insufficient GPU memory. The job then continued polling the unreachable backends even though their processes had already exited.
A representative example is PR #1027, attempt 2:

• K8s discovery test timed out
• Static backends subsequently failed to start because of insufficient GPU memory
• Static backend logs

This PR improves failure handling and observability in the router E2E workflow:

• always uninstall the K8s discovery Helm release after the test step, including when the step times out.

• track the two static backend processes while waiting for them to become reachable, fail immediately if either backend exits during startup.

• print the last 50 lines of the relevant backend log.

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[gemini-code-assist]

Code Review

This pull request enhances the wait-for-backends.sh script by introducing process ID and log file tracking for the backends, allowing the script to fail early and print diagnostic logs if a backend exits. The review feedback suggests making the script more robust under set -e by ensuring print_backend_log always returns 0 and explicitly returning 0 from check_backend_process to avoid implicit exit status issues.

[gemini-code-assist]

Since print_backend_log is a diagnostic helper, any failure within it (e.g., if tail fails due to permission issues or if the file is removed) should not cause the entire script to exit under set -e.

To prevent this, we should ensure the function always returns 0 by appending || true to the tail command and adding an explicit return 0 at the end of the function.

Suggested change

	print_backend_log() {
	local backend_name=$1
	local log_file=$2
	if [ -n "$log_file" ] && [ -f "$log_file" ]; then
	echo "Last 50 lines from ${backend_name} log (${log_file}):"
	tail -n 50 "$log_file"
	fi
	}
	print_backend_log() {
	local backend_name=$1
	local log_file=$2
	if [ -n "$log_file" ] && [ -f "$log_file" ]; then
	echo "Last 50 lines from ${backend_name} log (${log_file}):"
	tail -n 50 "$log_file" || true
	fi
	return 0
	}

[gemini-code-assist]

In Bash, if a function finishes without an explicit return, its exit status is that of the last executed command. If the if condition is false, the if statement returns 0, but relying on this implicit behavior can be fragile and less readable.

Adding an explicit return 0 at the end of check_backend_process makes the success path clear and robust.

Suggested change

	check_backend_process() {
	local backend_name=$1
	local backend_pid=$2
	local log_file=$3
	if [ -n "$backend_pid" ] && ! kill -0 "$backend_pid" 2>/dev/null; then
	echo "❌ ${backend_name} process exited before becoming reachable"
	print_backend_log "$backend_name" "$log_file"
	return 1
	fi
	}
	check_backend_process() {
	local backend_name=$1
	local backend_pid=$2
	local log_file=$3
	if [ -n "$backend_pid" ] && ! kill -0 "$backend_pid" 2>/dev/null; then
	echo "❌ ${backend_name} process exited before becoming reachable"
	print_backend_log "$backend_name" "$log_file"
	return 1
	fi
	return 0
	}

[ruizhang0101]

LGTM