multi_line_start_pattern value should be validated on launch

[motooka]

Describe the bug When a user uses a malformed regexp as multi_line_start_pattern value, the command exists successfully but logs are not submitted to CloudWatch Logs.

Steps to reproduce

• create a configuration file, with multi_line_start_pattern setting for a log, but the multi_line_start_pattern value is not a correct regexp.
• execute /opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl -a fetch-config -m ec2 -s -c file:/opt/aws/amazon-cloudwatch-agent/bin/config.json as a root user

What did you expect to see?

• the command amazon-cloudwatch-agent-ctl exits with non-zero status code
• the command amazon-cloudwatch-agent-ctl DOES NOT say Configuration validation succeeded

What did you see instead?

• the command amazon-cloudwatch-agent-ctl exits with 0 status code
• the command amazon-cloudwatch-agent-ctl DOES say Configuration validation succeeded
• the log file /opt/aws/amazon-cloudwatch-agent/logs/amazon-cloudwatch-agent.log is filled with a log message W! [inputs.logfile] not started with file state folder %s/opt/aws/amazon-cloudwatch-agent/logs/state. This log entry comes every seconds.

What version did you use? Version: 1.300031.0b313

What config did you use? logs section

"logs": {
	"logs_collected": {
		"files": {
			"collect_list": [
				{
					"file_path": "/var/log/foo.log",
					"log_group_name": "foolog",
					"log_stream_name": "{instance_id}",
					"multi_line_start_pattern": "*",
					"retention_in_days": -1
				}
			]
		}
	}
},

Environment OS: Ubuntu 22.04 on EC2

Additional context

• if the multi_line_start_pattern value is an empty string, the validation process fails as expected.
• current documentation does not provide any example for multi_line_start_pattern regexp. I guess some examples in this document might also be effective to prevent users from wasting long time.

[github-actions[bot]]

This issue was marked stale due to lack of activity.

[github-actions[bot]]

Closing this because it has stalled. Feel free to reopen if this issue is still relevant, or to ping the collaborator who labeled it stalled if you have any questions.