# Logstash Issue: Glob did not work, collector name {:name=\>"ConcurrentMarkSweep"} **URL:** \ **Category:** Logstash\ **Created:** [May 31, 2018, 4:23am UTC](https://discuss.elastic.co/t/logstash-issue-glob-did-not-work-collector-name-name-concurrentmarksweep/133964 "2018-05-31T04:23:50Z")\ **Posts on this page:** 1\ **Showing post:** 5
**Author:** ![magnusbaeck](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/magnusbaeck/32/44943_2.png) [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)\ **Post date:** [May 31, 2018, 6:04am UTC](https://discuss.elastic.co/t/logstash-issue-glob-did-not-work-collector-name-name-concurrentmarksweep/133964/5 "2018-05-31T06:04:55Z")
> 1. why did that happen without changing any configuration? Why did what happen? If it started working after you changed "null" to "nul" then you certainly changed the configuration. > 1. what's the importance of since\_db file. I don't think it's mandatory specifying in a configuration file? No, but setting it to "nul" or "/dev/null" (depending on your OS) will make Logstash oblivious to any old saved state about the current position in the file. The file input documentation has a few paragraphs on sincedb files. Please read them. > 1. difference between forward and backward slashes for specifying file path? Well, it seems Ruby or some Ruby library used by Logstash works better with forward slashes, even on Windows. > 1. what exactly are globbed files and what is glob did not work? A filename glob is a filename pattern that may or may not include wildcards. A glob that doesn't work is a glob that doesn't expand to any actual files. See [glob (programming) - Wikipedia](https://en.wikipedia.org/wiki/Glob_(programming)). --- _[View the full topic](https://discuss.elastic.co/t/logstash-issue-glob-did-not-work-collector-name-name-concurrentmarksweep/133964)._