# Logstash Input UDP problem

**URL:** https://discuss.elastic.co/t/logstash-input-udp-problem/49718
**Category:** Logstash
**Created:** [May 11, 2016, 2:32am UTC](https://discuss.elastic.co/t/logstash-input-udp-problem/49718 "2016-05-11T02:32:06Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Yim\_JunHyeok](https://avatars.discourse-cdn.com/v4/letter/y/e79b87/32.png) [@Yim\_JunHyeok](https://discuss.elastic.co/u/Yim_JunHyeok)
#### Post date: [May 11, 2016, 2:32am UTC](https://discuss.elastic.co/t/logstash-input-udp-problem/49718/1 "2016-05-11T02:32:06Z")

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First of all sorry for my bad english.

I'm doing logstash input UDP performance test.  
Unfortunately every time when i proceed logstash, i'm facing data loss. not sure where i am going wrong.

I Followed below steps.  
1.Send packets to the server(515 port)  
2.logstash input udp handle the packets and output generate file.

My logstash configuration

input {  
udp {  
workers =\> 8  
buffer\_size =\> 81920  
queue\_size =\> 15000  
port =\> 515  
type =\> "performance"  
}  
}

filter {}

output {  
file {  
#flush\_interval =\> 0  
path =\> ["/logstash.log"]  
}  
}

tcpdump result  
 ![](https://us1.discourse-cdn.com/elastic/original/2X/4/4e916bbf50dbe5af46a5d65ed7d7579d722348fc.png)

logstash output result

 ![](https://us1.discourse-cdn.com/elastic/original/2X/5/5ba9fea9d38b3792a545c3b9457f9fc63ca504f7.png)

tcpdump shows 10000 packets captured but logstash output file show only 6955 lines.  
Logstash is running on 8 core machine.

Can anyone suggest me where the configuration is wrong?

---

<div class="post-metadata">

### Author: ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)
#### Post date: [May 11, 2016, 11:57pm UTC](https://discuss.elastic.co/t/logstash-input-udp-problem/49718/2 "2016-05-11T23:57:58Z")

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UDP is not guaranteed delivery.

---

<div class="post-metadata">

### Author: ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 6, 2017, 4:57am UTC](https://discuss.elastic.co/t/logstash-input-udp-problem/49718/3 "2017-07-06T04:57:59Z")

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