Splunk alert for missing logs

Hi, Below is a snippet of log pattern generating tons of record. Intending to write a alert if any log are missing for given time time range. sourcetype source activity sourcetype1 myLog.log activity1 sourcetype1 myLog.log activity2 sourcetype2 myLog.log activity3 sourcetype2 myLog.log activity3 sourcetype3 myLog.log activity1 sourcetype3 myLog.log activity2 sourcetype3 myLog.log activity3 Is a search, lookup or simple individual query on sourcetype best approach for making sure logs are generated for each sourcetype? Looking for best approach. Thanks.