# Multiple logstash nodes use file-output plugin to output messages to one file in a shared file system?

**URL:** <https://discuss.elastic.co/t/multiple-logstash-nodes-use-file-output-plugin-to-output-messages-to-one-file-in-a-shared-file-system/94275>\
**Category:** Logstash\
**Created:** [July 24, 2017, 6:32am UTC](https://discuss.elastic.co/t/multiple-logstash-nodes-use-file-output-plugin-to-output-messages-to-one-file-in-a-shared-file-system/94275 "2017-07-24T06:32:42Z")\
**Posts on this page:** 1\
**Showing post:** 9

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**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:** [July 26, 2017, 7:41am UTC](https://discuss.elastic.co/t/multiple-logstash-nodes-use-file-output-plugin-to-output-messages-to-one-file-in-a-shared-file-system/94275/9 "2017-07-26T07:41:31Z")

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> As there is no coordination around file writing between the Logstash instances, I would expect writing to a shared file to cause serious problems.

If Logstash is opening the output file with O\_APPEND (which it should) then all write() operations will be made at the end of the file even if multiple processes write to the file concurrently. See [write](http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html). This doesn't apply to Windows though.

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