# Does First Input First Output in logstash **URL:** \ **Category:** Logstash\ **Created:** [November 16, 2017, 2:22am UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850 "2017-11-16T02:22:15Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![lsyoung](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/lsyoung/32/90815_2.png) [@lsyoung](https://discuss.elastic.co/u/lsyoung)\ **Post date:** [November 16, 2017, 2:22am UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850/1 "2017-11-16T02:22:15Z")
Can logstash ensure the message first read by input-plugin can be output firstly with output-plugin? AND If if the output-plugin is elasticsearch, does the the docs write into elasticsearch by the same sequence with the input-plugin read? BECAUSE, I want to update the previous data with the data behind. Anyone can help, Thanks!!! ---
**Author:** ![guyboertje](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/guyboertje/32/31592_2.png) [@guyboertje](https://discuss.elastic.co/u/guyboertje)\ **Post date:** [November 16, 2017, 9:20am UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850/2 "2017-11-16T09:20:22Z")
The worker threads can arrive at an output in any order because the any thread can be delayed relative to the other. For strict in-order processing you need to have only 1 worker thread. Setting `pipeline.workers`. For version 5.6 read [https://www.elastic.co/guide/en/logstash/5.6/logstash-settings-file.html](https://www.elastic.co/guide/en/logstash/5.6/logstash-settings-file.html) For version 6.0 read [https://www.elastic.co/guide/en/logstash/6.0/logstash-settings-file.html](https://www.elastic.co/guide/en/logstash/6.0/logstash-settings-file.html) **HOWEVER** If you are trying to overwrite earlier documents with later documents based on some identifier value then you need a different strategy. If you are looking for a kind of upsert, replace, overwrite or merge type action please say so, we can then help further. ---
**Author:** ![lsyoung](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/lsyoung/32/90815_2.png) [@lsyoung](https://discuss.elastic.co/u/lsyoung)\ **Post date:** [November 16, 2017, 10:07am UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850/3 "2017-11-16T10:07:50Z")
Thanks! YES, I want to delete the earlier document, any good advice? Tanks!!! When the `field1` is `"0"` I index a document, then when document with the same value of `field2` comes and `field1 != "0"` , I want to delete the document created before. I use this configure now: ``` input{} filter{ if [field1] == "0"{ mutate{ add_field =>{ "[@metadata][action]" => "index" } } }else { mutate{ add_field =>{ "[@metadata][action]" => "delete" } } } } output{ elasticsearch { hosts => ["XXXX"] index => "XXXX" document_id => "%{field2}" action => "%{[@metadata][action]}" document_type => "%{type}" flush_size => 300 idle_flush_time => 10 sniffing => false codec => "json" } } ``` ---
**Author:** ![guyboertje](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/guyboertje/32/31592_2.png) [@guyboertje](https://discuss.elastic.co/u/guyboertje)\ **Post date:** [November 16, 2017, 1:09pm UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850/4 "2017-11-16T13:09:08Z")
This [link](https://www.elastic.co/guide/en/elasticsearch/reference/5.6/_modifying_your_data.html#_indexing_replacing_documents) shows that you can use the document\_id to overwrite the previous doc with the index action. However, you have some logic to implement and a consideration of timing, I think. I'm confused. Your first post says that you want to update older docs but your newer post seems to say this: Documents will only remain in the index if no other docs having the same id AND field1 != 0 are ingested. ---
**Author:** ![lsyoung](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/lsyoung/32/90815_2.png) [@lsyoung](https://discuss.elastic.co/u/lsyoung)\ **Post date:** [November 16, 2017, 1:58pm UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850/5 "2017-11-16T13:58:53Z")
> [@guyboertje](#): > > Documents will only remain in the index if no other docs having the same id AND field1 != 0 are ingested. That is my goal. In my first post, I when I say `update the data` I mean delete it, sorry for not saying clearly. So, if I want to use logstash to achieve my goal, setting `pipeline.workers` to 1 will help. I will try it. Thanks for patiently answering my question! ---
**Author:** ![guyboertje](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/guyboertje/32/31592_2.png) [@guyboertje](https://discuss.elastic.co/u/guyboertje)\ **Post date:** [November 16, 2017, 2:58pm UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850/6 "2017-11-16T14:58:03Z")
> [@lsyoung](#): > > document\_id =\> "%{filed2}" Good luck! make sure you have the correct spelling in `document_id` setting. ---
**Author:** ![lsyoung](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/lsyoung/32/90815_2.png) [@lsyoung](https://discuss.elastic.co/u/lsyoung)\ **Post date:** [November 17, 2017, 3:23am UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850/7 "2017-11-17T03:23:56Z")
`field2` is not what I actually used, it's a an example. Anyway, thank you for your reminder, I will correct it. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [December 15, 2017, 3:24am UTC](https://discuss.elastic.co/t/does-first-input-first-output-in-logstash/107850/8 "2017-12-15T03:24:40Z")
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