Opster Team
Last updated: Mar 30, 2021
| 1 min readIn addition to reading this guide, we recommend you run the Elasticsearch Health Check-Up. It will detect issues and improve your Elasticsearch performance by analyzing your shard sizes, threadpools, memory, snapshots, disk watermarks and more.The Elasticsearch Check-Up is free and requires no installation.
Overview
In Elasticsearch, routing refers to document routing. When you index a document, Elasticsearch will determine which shard the document should be routed to for indexing.
The shard is selected based on the following formula:
shard = hash(_routing) % number_of_primary_shards
Where the default value of _routing is _id.
It is important to know which shard the document is routed to, because Elasticsearch will need to determine where to find that document later on for document retrieval requests.
Examples
In twitter index with 2 primary shards, the document with _id equal to “440” gets routed to the shard number:
shard = hash( 440 ) % 2 PUT twitter/_doc/440 { ... }
Notes and good things to know
- In order to improve search speed, you can create custom routing. For example, you can enable custom routing that will ensure that only a single shard will be queried (the shard that contains your data).
- To create custom routing in Elasticsearch, you will need to configure and define that not all routing will be completed by default settings. ( v <= 5.0)
PUT my_index/customer/_mapping { "order":{ "_routing":{ "required":true } } }
- This will ensure that every document in the “customer” type must specify a custom routing. For Elasticsearch version 6 or above you will need to update the same mapping as:
PUT my_index/_mapping { "order":{ "_routing":{ "required":true } } }
Related log errors to this ES concept
< Page: 1 of 4 >
Find & fix Elasticsearch problems
Opster AutoOps diagnoses & fixes issues in Elasticsearch based on analyzing hundreds of metrics.
Fix Your Cluster IssuesConnect in under 2 minutes
Billy McCarthy
Senior SysAdmin at Backblaze