# What is the meaning of throttle\_time\_in\_millis? **URL:** \ **Category:** Elasticsearch\ **Created:** [March 4, 2014, 7:39am UTC](https://discuss.elastic.co/t/what-is-the-meaning-of-throttle-time-in-millis/16128 "2014-03-04T07:39:10Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Isaac\_Hazan](https://avatars.discourse-cdn.com/v4/letter/i/a5b964/32.png) [@Isaac\_Hazan](https://discuss.elastic.co/u/Isaac_Hazan)\ **Post date:** [March 4, 2014, 7:39am UTC](https://discuss.elastic.co/t/what-is-the-meaning-of-throttle-time-in-millis/16128/1 "2014-03-04T07:39:10Z")
I created an index in a 4 nodes Elasticsearch cluster. I added about 3.5 M documents using the java Elasticsearch API. When asking for the stats i get a very high number in throttle\_time\_in\_millis as follows: { "\_shards": { "total": 10, "successful": 10, "failed": 0 }, "\_all": { "primaries": { "docs": { "count": 3855540, "deleted": 0 }, "store": { "size\_in\_bytes": 1203074796, "throttle\_time\_in\_millis": 980255 }, "indexing": { "index\_total": 3855540, "index\_time\_in\_millis": 426300, "index\_current": 0, "delete\_total": 0, "delete\_time\_in\_millis": 0, "delete\_current": 0 }, 1. What is the meaning of throttle\_time\_in\_millis? 2. What could be the reason for this to increase? Thx in advance -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![jpountz](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jpountz/32/45836_2.png) [@jpountz](https://discuss.elastic.co/u/jpountz)\ **Post date:** [March 4, 2014, 1:59pm UTC](https://discuss.elastic.co/t/what-is-the-meaning-of-throttle-time-in-millis/16128/2 "2014-03-04T13:59:19Z")
When you add documents to Elasticsearch, this creates new files on disk that form what is called a segment. Having several segments is fine, but when you start having too many of them, search is going to be slower this is why Elasticsearch has a background process that takes care of merging these segments, so that the total number of segments remains low enough (usually in the order of ~50 per shard). However, running a background merge can take lots of resources on the server, especially I/O, and this might defeat the purpose of making search remain fast since search operations don't have much I/O capacity left. In order to prevent it from happening, merges are throttled[1], meaning that they can't write more than X bytes of data per second. If they try to, Elasticsearch will pause them for a while before they can keep on merging again. The throttle\_time reported by the stats API gives you the total number of time that merges have been paused in order to prevent them from stealing all the server I/O. [1] > **[Elasticsearch Platform — Find real-time answers at scale](https://www.elastic.co)** > > Power insights and outcomes with the Elasticsearch Platform and AI. See into your data and find answers that matter with enterprise solutions designed to help you build, observe, and protect. Try Elasticsearch free today. On Tue, Mar 4, 2014 at 8:39 AM, Isaac Hazan [isaac.yann.hazan@gmail.com](mailto:isaac.yann.hazan@gmail.com)wrote: > I created an index in a 4 nodes Elasticsearch cluster. I added about 3.5 M > documents using the java Elasticsearch API. > When asking for the stats i get a very high number in > throttle\_time\_in\_millis as follows: > > { > "\_shards": { > "total": 10, > "successful": 10, > "failed": 0 > }, > "\_all": { > "primaries": { > "docs": { > "count": 3855540, > "deleted": 0 > }, > "store": { > "size\_in\_bytes": 1203074796, > "throttle\_time\_in\_millis": 980255 > }, > "indexing": { > "index\_total": 3855540, > "index\_time\_in\_millis": 426300, > "index\_current": 0, > "delete\_total": 0, > "delete\_time\_in\_millis": 0, > "delete\_current": 0 > }, > > 1. What is the meaning of throttle\_time\_in\_millis? > 2. What could be the reason for this to increase? > > Thx in advance > > -- > You received this message because you are subscribed to the Google Groups > "elasticsearch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). > To view this discussion on the web visit > [https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com)[https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com?utm_medium=email&utm_source=footer) > . > For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). -- Adrien Grand -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j7RW1YhyZYBKxXQ183yjSTX-aMXipBR8DZatCmkFRQp4g%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j7RW1YhyZYBKxXQ183yjSTX-aMXipBR8DZatCmkFRQp4g%40mail.gmail.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![Isaac\_Hazan](https://avatars.discourse-cdn.com/v4/letter/i/a5b964/32.png) [@Isaac\_Hazan](https://discuss.elastic.co/u/Isaac_Hazan)\ **Post date:** [March 4, 2014, 3:01pm UTC](https://discuss.elastic.co/t/what-is-the-meaning-of-throttle-time-in-millis/16128/3 "2014-03-04T15:01:17Z")
Thx. Is a segment a single file with multiple documents? Or is it multiple files that together form a segment? In other terms I don't fully understand why the notion of segment exists? Does the fact that I have a high number in the throttling KPI mean that I have a problem in performance and if so is there a setting to tune it properly? Thx From: [elasticsearch@googlegroups.com](mailto:elasticsearch@googlegroups.com) [[mailto:elasticsearch@googlegroups.com](mailto:elasticsearch@googlegroups.com)] On Behalf Of Adrien Grand Sent: Tuesday, March 04, 2014 3:59 PM To: [elasticsearch@googlegroups.com](mailto:elasticsearch@googlegroups.com) Subject: Re: What is the meaning of throttle\_time\_in\_millis? When you add documents to Elasticsearch, this creates new files on disk that form what is called a segment. Having several segments is fine, but when you start having too many of them, search is going to be slower this is why Elasticsearch has a background process that takes care of merging these segments, so that the total number of segments remains low enough (usually in the order of ~50 per shard). However, running a background merge can take lots of resources on the server, especially I/O, and this might defeat the purpose of making search remain fast since search operations don't have much I/O capacity left. In order to prevent it from happening, merges are throttled[1], meaning that they can't write more than X bytes of data per second. If they try to, Elasticsearch will pause them for a while before they can keep on merging again. The throttle\_time reported by the stats API gives you the total number of time that merges have been paused in order to prevent them from stealing all the server I/O. [1] > **[Elasticsearch Platform — Find real-time answers at scale](https://www.elastic.co)** > > Power insights and outcomes with the Elasticsearch Platform and AI. See into your data and find answers that matter with enterprise solutions designed to help you build, observe, and protect. Try Elasticsearch free today. modules-store.html#store-throttling On Tue, Mar 4, 2014 at 8:39 AM, Isaac Hazan [isaac.yann.hazan@gmail.com](mailto:isaac.yann.hazan@gmail.com) wrote: I created an index in a 4 nodes Elasticsearch cluster. I added about 3.5 M documents using the java Elasticsearch API. When asking for the stats i get a very high number in throttle\_time\_in\_millis as follows: { "\_shards": { ``` "total": 10, "successful": 10, "failed": 0 ``` }, "\_all": { ``` "primaries": { "docs": { "count": 3855540, "deleted": 0 }, "store": { "size_in_bytes": 1203074796, "throttle_time_in_millis": 980255 }, "indexing": { "index_total": 3855540, "index_time_in_millis": 426300, "index_current": 0, "delete_total": 0, "delete_time_in_millis": 0, "delete_current": 0 }, ``` 1. What is the meaning of throttle\_time\_in\_millis? 2. What could be the reason for this to increase? Thx in advance -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6](https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6) cff5cd47%[40googlegroups.com](http://40googlegroups.com) \<[https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de](https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de) 6cff5cd47%[40GGGROUPS CASINO – Real Slot Casino for 10,000+ Senior Players](http://40googlegroups.com?utm_medium=email&utm_source=footer)\> . For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). -- Adrien Grand -- You received this message because you are subscribed to a topic in the Google Groups "elasticsearch" group. To unsubscribe from this topic, visit [https://groups.google.com/d/topic/elasticsearch/K9GiA2KDwoA/unsubscribe](https://groups.google.com/d/topic/elasticsearch/K9GiA2KDwoA/unsubscribe). 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**Author:** ![gkwelding](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/gkwelding/32/1658_2.png) [@gkwelding](https://discuss.elastic.co/u/gkwelding)\ **Post date:** [March 4, 2014, 3:23pm UTC](https://discuss.elastic.co/t/what-is-the-meaning-of-throttle-time-in-millis/16128/4 "2014-03-04T15:23:35Z")
Isaac, this ([Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/index-modules-merge.html)) gives a good explanation on what segments actually are. It also gives you the list of settings to do with merges and maybe you can find some optimisations in there somewhere. On Tuesday, March 4, 2014 3:01:17 PM UTC, Isaac Hazan wrote: > Thx. > > Is a segment a single file with multiple documents? Or is it multiple > files that together form a segment? In other terms I don’t fully understand > why the notion of segment exists? > > Does the fact that I have a high number in the throttling KPI mean that I > have a problem in performance and if so is there a setting to tune it > properly? > > Thx > > _From:_ [elasti...@googlegroups.com](mailto:elasti...@googlegroups.com) \ [mailto: > [elasti...@googlegroups.com](mailto:elasti...@googlegroups.com) \] \*On Behalf Of \*Adrien Grand > _Sent:_ Tuesday, March 04, 2014 3:59 PM > _To:_ [elasti...@googlegroups.com](mailto:elasti...@googlegroups.com) \ > _Subject:_ Re: What is the meaning of throttle\_time\_in\_millis? > > When you add documents to Elasticsearch, this creates new files on disk > that form what is called a segment. Having several segments is fine, but > when you start having too many of them, search is going to be slower this > is why Elasticsearch has a background process that takes care of merging > these segments, so that the total number of segments remains low enough > (usually in the order of ~50 per shard). However, running a background > merge can take lots of resources on the server, especially I/O, and this > might defeat the purpose of making search remain fast since search > operations don't have much I/O capacity left. In order to prevent it from > happening, merges are throttled[1], meaning that they can't write more than > X bytes of data per second. If they try to, Elasticsearch will pause them > for a while before they can keep on merging again. > > The throttle\_time reported by the stats API gives you the total number of > time that merges have been paused in order to prevent them from stealing > all the server I/O. > > [1] > [Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/index-modules-store.html#store-throttling) > > On Tue, Mar 4, 2014 at 8:39 AM, Isaac Hazan \<[isaac.ya...@gmail.com](mailto:isaac.ya...@gmail.com)\\> > wrote: > > I created an index in a 4 nodes Elasticsearch cluster. I added about 3.5 M > documents using the java Elasticsearch API. > > When asking for the stats i get a very high number in > throttle\_time\_in\_millis as follows: > > { > > "\_shards": { > > ``` > "total": 10, > > "successful": 10, > > "failed": 0 > > ``` > > }, > > "\_all": { > > ``` > "primaries": { > > "docs": { > > "count": 3855540, > > "deleted": 0 > > }, > > "store": { > > "size_in_bytes": 1203074796, > > "throttle_time_in_millis": 980255 > > }, > > "indexing": { > > "index_total": 3855540, > > "index_time_in_millis": 426300, > > "index_current": 0, > > "delete_total": 0, > > "delete_time_in_millis": 0, > > "delete_current": 0 > > }, > > ``` > > 1. What is the meaning of throttle\_time\_in\_millis? > > 2. What could be the reason for this to increase? > > Thx in advance > > -- > You received this message because you are subscribed to the Google Groups > "elasticsearch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [elasticsearc...@googlegroups.com](mailto:elasticsearc...@googlegroups.com) \. > To view this discussion on the web visit > [https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com)[https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/73633235-ae82-4cd2-a74a-3de6cff5cd47%40googlegroups.com?utm_medium=email&utm_source=footer) > . > For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). > > -- > > Adrien Grand > > -- > You received this message because you are subscribed to a topic in the > Google Groups "elasticsearch" group. > To unsubscribe from this topic, visit > [https://groups.google.com/d/topic/elasticsearch/K9GiA2KDwoA/unsubscribe](https://groups.google.com/d/topic/elasticsearch/K9GiA2KDwoA/unsubscribe). > To unsubscribe from this group and all its topics, send an email to > [elasticsearc...@googlegroups.com](mailto:elasticsearc...@googlegroups.com) \. > To view this discussion on the web visit > [https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j7RW1YhyZYBKxXQ183yjSTX-aMXipBR8DZatCmkFRQp4g%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j7RW1YhyZYBKxXQ183yjSTX-aMXipBR8DZatCmkFRQp4g%40mail.gmail.com)[https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j7RW1YhyZYBKxXQ183yjSTX-aMXipBR8DZatCmkFRQp4g%40mail.gmail.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j7RW1YhyZYBKxXQ183yjSTX-aMXipBR8DZatCmkFRQp4g%40mail.gmail.com?utm_medium=email&utm_source=footer) > . > For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/db9e02e8-5fb6-4510-81f2-49b3b92fa44b%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/db9e02e8-5fb6-4510-81f2-49b3b92fa44b%40googlegroups.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![jpountz](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jpountz/32/45836_2.png) [@jpountz](https://discuss.elastic.co/u/jpountz)\ **Post date:** [March 4, 2014, 4:08pm UTC](https://discuss.elastic.co/t/what-is-the-meaning-of-throttle-time-in-millis/16128/5 "2014-03-04T16:08:47Z")
On Tue, Mar 4, 2014 at 4:01 PM, isaac hazan [isaac.yann.hazan@gmail.com](mailto:isaac.yann.hazan@gmail.com)wrote: > Thx. > > Is a segment a single file with multiple documents? Or is it multiple > files that together form a segment? In other terms I don't fully understand > why the notion of segment exists? The simple answer is that a segment is made of several files. Typically, there is one that is used to store "stored fields" (allowing to get the original field values given a document ID), one for the terms dictionary (the unique terms in your documents), one for postings lists (which given a term can return the list of documents that contain this term), one for deleted documents, etc. And an index is the union of several segments. Searching an index is effectively searching every segment and merging results together. But for your information, there is an optimization called "compound file" which allows to store all these logical files of one segment in a single physical file when the segment is small. This helps save file descriptors. > Does the fact that I have a high number in the throttling KPI mean that > I have a problem in performance and if so is there a setting to tune it > properly? A high throttling time is not necessarily an issue, it just means that merges have been occasionally paused so that search remains fast. You can disable merge throttling if you want by setting index.store.throttle.max\_bytes\_per\_sec[1] to -1. [1] > **[Elasticsearch Platform — Find real-time answers at scale](https://www.elastic.co)** > > Power insights and outcomes with the Elasticsearch Platform and AI. See into your data and find answers that matter with enterprise solutions designed to help you build, observe, and protect. Try Elasticsearch free today. -- Adrien Grand -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j7ww%3Dw8f\_b-HyPiMPnc5QZwcb6%3DGFPJzD46o%2BePnOa\_4A%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j7ww%3Dw8f_b-HyPiMPnc5QZwcb6%3DGFPJzD46o%2BePnOa_4A%40mail.gmail.com). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**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, 1:45am UTC](https://discuss.elastic.co/t/what-is-the-meaning-of-throttle-time-in-millis/16128/6 "2017-07-06T01:45:49Z")