# What is "lock-step" in load balancing mode?

**URL:** <https://discuss.elastic.co/t/what-is-lock-step-in-load-balancing-mode/65602>\
**Category:** Beats\
**Created:** [November 10, 2016, 8:34am UTC](https://discuss.elastic.co/t/what-is-lock-step-in-load-balancing-mode/65602 "2016-11-10T08:34:07Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![YuWatanabe](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/yuwatanabe/32/13259_2.png) [@YuWatanabe](https://discuss.elastic.co/u/YuWatanabe)\
**Post date:** [November 10, 2016, 8:34am UTC](https://discuss.elastic.co/t/what-is-lock-step-in-load-balancing-mode/65602/1 "2016-11-10T08:34:07Z")

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I am setting up load balancing configuration referencing the [document](https://www.elastic.co/guide/en/beats/filebeat/current/load-balancing.html)  
I found **lock step** mode but due to lack of my knowledge , I dont understand what this do.

I have tested comparing with the regular mode by sending two logs sequentially to two logstash nodes but it seems to send to only one logstash.

How does this "lock step" mode behave and when should you use this mode?

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**Author:** ![steffens](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/steffens/32/79630_2.png) [@steffens](https://discuss.elastic.co/u/steffens)\
**Post date:** [November 10, 2016, 12:57pm UTC](https://discuss.elastic.co/t/what-is-lock-step-in-load-balancing-mode/65602/2 "2016-11-10T12:57:22Z")

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The regular mode will send logs sequentially to one node at a time. No matter how many nodes you have configured.

In "lock step" mode, the batch collected by the spooler is split up into smaller batches of size `bulk_max_size`. These smaller batches are load-balanced between available connections. Only after all sub-batches have been published, another batch is retrieved from the spooler. "lock step" stands for: waiting for all sub-batches being published.

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<div class="post-metadata">

**Author:** ![dedemorton](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dedemorton/32/84409_2.png) [@dedemorton](https://discuss.elastic.co/u/dedemorton)\
**Post date:** [November 10, 2016, 6:14pm UTC](https://discuss.elastic.co/t/what-is-lock-step-in-load-balancing-mode/65602/3 "2016-11-10T18:14:09Z")

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I've created an issue in GitHub to add some clarification to the docs:

> <https://github.com/elastic/beats/issues/2981>

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [December 1, 2016, 8:34am UTC](https://discuss.elastic.co/t/what-is-lock-step-in-load-balancing-mode/65602/4 "2016-12-01T08:34:26Z")

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