# Hashing algo. for Routing **URL:** \ **Category:** Elasticsearch\ **Created:** [September 2, 2013, 7:41am UTC](https://discuss.elastic.co/t/hashing-algo-for-routing/13428 "2013-09-02T07:41:11Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Anand\_Nalya](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/anand_nalya/32/571_2.png) [@Anand\_Nalya](https://discuss.elastic.co/u/Anand_Nalya)\ **Post date:** [September 2, 2013, 7:41am UTC](https://discuss.elastic.co/t/hashing-algo-for-routing/13428/1 "2013-09-02T07:41:11Z")
Hi, I wanted to know which hashing algorithm is used by ES for sharding. I can find 2 in [https://github.com/elasticsearch/elasticsearch/tree/master/src/main/java/org/elasticsearch/cluster/routing/operation/hash](https://github.com/elasticsearch/elasticsearch/tree/master/src/main/java/org/elasticsearch/cluster/routing/operation/hash). Also, is there a way of specifying a custom hashing algorithm? The problem I'm trying to solve is that the no. of routing keys that I have is around 2 times the number of shards in the index and I want each shard to support two routing keys. Thanks, Anand -- 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). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![javanna](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/javanna/32/4698_2.png) [@javanna](https://discuss.elastic.co/u/javanna)\ **Post date:** [September 2, 2013, 4:06pm UTC](https://discuss.elastic.co/t/hashing-algo-for-routing/13428/2 "2013-09-02T16:06:51Z")
Hi, have a look at OperationRoutingModule[https://github.com/elasticsearch/elasticsearch/blob/master/src/main/java/org/elasticsearch/cluster/routing/operation/OperationRoutingModule.java](https://github.com/elasticsearch/elasticsearch/blob/master/src/main/java/org/elasticsearch/cluster/routing/operation/OperationRoutingModule.java)to find out more. That's the guice module that loads by default the DjbHashFunction. Never tried it myself but it looks like it's also possible to plug in a custom hash function that implements the HashFunction interface, using the cluster.routing.operation.hash.type setting. Hope this helps Luca On Monday, September 2, 2013 9:41:11 AM UTC+2, Anand Nalya wrote: > Hi, > > I wanted to know which hashing algorithm is used by ES for sharding. I can > find 2 in > [https://github.com/elasticsearch/elasticsearch/tree/master/src/main/java/org/elasticsearch/cluster/routing/operation/hash](https://github.com/elasticsearch/elasticsearch/tree/master/src/main/java/org/elasticsearch/cluster/routing/operation/hash) > . > > Also, is there a way of specifying a custom hashing algorithm? The problem > I'm trying to solve is that the no. of routing keys that I have is around 2 > times the number of shards in the index and I want each shard to support > two routing keys. > > Thanks, > Anand -- 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). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![javanna](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/javanna/32/4698_2.png) [@javanna](https://discuss.elastic.co/u/javanna)\ **Post date:** [September 11, 2013, 2:16pm UTC](https://discuss.elastic.co/t/hashing-algo-for-routing/13428/3 "2013-09-11T14:16:12Z")
Hi Anand, any news? Looking back at your question, I wonder why you need to write a custom hashing algorithm. Can't you just use custom routing? Would love to know more about your usecase. Cheers Luca On Monday, September 2, 2013 6:06:51 PM UTC+2, Luca Cavanna wrote: > Hi, > have a look at OperationRoutingModule[https://github.com/elasticsearch/elasticsearch/blob/master/src/main/java/org/elasticsearch/cluster/routing/operation/OperationRoutingModule.java](https://github.com/elasticsearch/elasticsearch/blob/master/src/main/java/org/elasticsearch/cluster/routing/operation/OperationRoutingModule.java)to find out more. That's the guice module that loads by default > the DjbHashFunction. Never tried it myself but it looks like it's also > possible to plug in a custom hash function that implements the HashFunction > interface, using the cluster.routing.operation.hash.type setting. > > Hope this helps > Luca > > On Monday, September 2, 2013 9:41:11 AM UTC+2, Anand Nalya wrote: > > > Hi, > > > > I wanted to know which hashing algorithm is used by ES for sharding. I > > can find 2 in > > [https://github.com/elasticsearch/elasticsearch/tree/master/src/main/java/org/elasticsearch/cluster/routing/operation/hash](https://github.com/elasticsearch/elasticsearch/tree/master/src/main/java/org/elasticsearch/cluster/routing/operation/hash) > > . > > > > Also, is there a way of specifying a custom hashing algorithm? The > > problem I'm trying to solve is that the no. of routing keys that I have is > > around 2 times the number of shards in the index and I want each shard to > > support two routing keys. > > > > Thanks, > > Anand -- 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). For more options, visit [https://groups.google.com/groups/opt\_out](https://groups.google.com/groups/opt_out). ---
**Author:** ![Anand\_Nalya](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/anand_nalya/32/571_2.png) [@Anand\_Nalya](https://discuss.elastic.co/u/Anand_Nalya)\ **Post date:** [September 12, 2013, 4:48am UTC](https://discuss.elastic.co/t/hashing-algo-for-routing/13428/4 "2013-09-12T04:48:38Z")
Hi Luca, My use case was to have completely predictable routing of documents at shard level. For example, I wanted to have the document with particular value of attribute a1 and a2 to go to shard0 and for some other combination to shard2. To solve this, I did use a custom routing algorithm that gives a routing value from _A_ to _(A+noOfShards-1)_. In this way even though I cannot pinpoint the actual shard where the data goes, I can be sure that data with routing key k and k+1 goes to adjacent shards. Anand On Wednesday, 11 September 2013 19:46:12 UTC+5:30, Luca Cavanna wrote: > Hi Anand, > any news? Looking back at your question, I wonder why you need to write a > custom hashing algorithm. Can't you just use custom routing? Would love to > know more about your usecase. > > Cheers > Luca > > On Monday, September 2, 2013 6:06:51 PM UTC+2, Luca Cavanna wrote: > > > Hi, > > have a look at OperationRoutingModule[https://github.com/elasticsearch/elasticsearch/blob/master/src/main/java/org/elasticsearch/cluster/routing/operation/OperationRoutingModule.java](https://github.com/elasticsearch/elasticsearch/blob/master/src/main/java/org/elasticsearch/cluster/routing/operation/OperationRoutingModule.java)to find out more. That's the guice module that loads by default > > the DjbHashFunction. Never tried it myself but it looks like it's also > > possible to plug in a custom hash function that implements the HashFunction > > interface, using the cluster.routing.operation.hash.type setting. > > > > Hope this helps > > Luca > > > > On Monday, September 2, 2013 9:41:11 AM UTC+2, Anand Nalya wrote: > > > > > Hi, > > > > > > I wanted to know which hashing algorithm is used by ES for sharding. I > > > can find 2 in > > > [https://github.com/elasticsearch/elasticsearch/tree/master/src/main/java/org/elasticsearch/cluster/routing/operation/hash](https://github.com/elasticsearch/elasticsearch/tree/master/src/main/java/org/elasticsearch/cluster/routing/operation/hash) > > > . > > > > > > Also, is there a way of specifying a custom hashing algorithm? The > > > problem I'm trying to solve is that the no. of routing keys that I have is > > > around 2 times the number of shards in the index and I want each shard to > > > support two routing keys. > > > > > > Thanks, > > > Anand -- 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). 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, 2:17am UTC](https://discuss.elastic.co/t/hashing-algo-for-routing/13428/5 "2017-07-06T02:17:02Z")