# Strange behaviour when using both Kafka output and input plugins
**URL:** https://discuss.elastic.co/t/strange-behaviour-when-using-both-kafka-output-and-input-plugins/59727
**Category:** Logstash
**Created:** [September 3, 2016, 12:34pm UTC](https://discuss.elastic.co/t/strange-behaviour-when-using-both-kafka-output-and-input-plugins/59727 "2016-09-03T12:34:03Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@ryac](https://discuss.elastic.co/u/ryac)
#### Post date: [September 3, 2016, 12:34pm UTC](https://discuss.elastic.co/t/strange-behaviour-when-using-both-kafka-output-and-input-plugins/59727/1 "2016-09-03T12:34:03Z")
Hi all,
Am I able to use both, the output and input Kafka plugins on the same Logstash instance? It seems that the configuration for the _consumer continuously loops through all messages in Kafka forever_. I'm following a structure similar to [this article](https://www.elastic.co/blog/just-enough-kafka-for-the-elastic-stack-part1), the diagram shown below:
```auto
Logstash (shipper) | --> Kafka --> | Logstash (indexer)
01.conf | | 02.conf
```
My 01.conf file is my producer to Kafka, and for testing it looks like this:
```auto
input {
stdin { }
}
output {
kafka {
topic_id => "topicname"
codec => json
}
}
```
It will be light, only sending logs to Kafka.
The configuration to consume Kafka messages (02.conf) looks like this:
```auto
input {
kafka {
topics => "topicname"
codec => json
}
}
output {
file {
path => "/var/www/test.log"
}
# elasticsearch { }
}
```
For testing, I run the following to load both confs:
`bin/logstash -f /etc/logstash/conf.d/`
And I get a message that says:
```auto
Settings: Default pipeline workers: 1
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-kafka-5.0.4/vendor/jar-dependencies/runtime-jars/slf4j-log4j12-1.7.13.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-kafka-5.0.4/vendor/jar-dependencies/runtime-jars/slf4j-log4j12-1.7.21.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
Pipeline main started
```
I'm running this on Ubuntu 14.04, Logstash 2.4, the plugin versions of Kafka are both 5.0.4, and Kafka 0.10.0.1.
If I test each config separately, I don't get this problem. It's only when I run both at the same time.
Any help would be greatly appreciated!
Thanks,
Ryan
---
### Author:  [@warkolm](https://discuss.elastic.co/u/warkolm)
#### Post date: [September 5, 2016, 6:41am UTC](https://discuss.elastic.co/t/strange-behaviour-when-using-both-kafka-output-and-input-plugins/59727/2 "2016-09-05T06:41:27Z")
When you have multiple files, LS merges them into one big one and then runs it.
---
### Author:  [@ryac](https://discuss.elastic.co/u/ryac)
#### Post date: [September 5, 2016, 8:31am UTC](https://discuss.elastic.co/t/strange-behaviour-when-using-both-kafka-output-and-input-plugins/59727/3 "2016-09-05T08:31:25Z")
I see.. so that causes the feedback loop.
What is the best way to solve this issue?
---
### Author:  [@bmaloney](https://discuss.elastic.co/u/bmaloney)
#### Post date: [September 16, 2016, 2:10pm UTC](https://discuss.elastic.co/t/strange-behaviour-when-using-both-kafka-output-and-input-plugins/59727/4 "2016-09-16T14:10:29Z")
Ryan, you should be able to solve your particular problem by running two completely separate instances of logstash (two startup scripts, two JVM's, etc).
I have the opposite problem, I want to use logstash to read from Kafka, doctor some messages, and write them into another topic, and unfortunately I can't use the trick to avoid the multiple SLF4J bindings bindings issue (unless I use a socket or something unreliable to pass between two logstashes).
---
### Author:  [@ryac](https://discuss.elastic.co/u/ryac)
#### Post date: [September 19, 2016, 2:36am UTC](https://discuss.elastic.co/t/strange-behaviour-when-using-both-kafka-output-and-input-plugins/59727/5 "2016-09-19T02:36:55Z")
Hi Brian, thanks for the clarification. That's what I thought.
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 6, 2017, 4:38am UTC](https://discuss.elastic.co/t/strange-behaviour-when-using-both-kafka-output-and-input-plugins/59727/6 "2017-07-06T04:38:02Z")