Elasticsearch is a distributed RESTful search engine built for the cloud. Features include:
First of all, DON’T PANIC. It will take 5 minutes to get the gist of what Elasticsearch is all about.
You need to have a recent version of Java installed. See the Setup page for more information.
bin/elasticsearch
on unix, or bin\elasticsearch.bat
on windows.curl -X GET http://localhost:9200/
.Let’s try and index some twitter like information. First, let’s index some tweets (the twitter
index will be created automatically):
curl -XPUT 'http://localhost:9200/twitter/doc/1?pretty' -H 'Content-Type: application/json' -d ' { "user": "kimchy", "post_date": "2009-11-15T13:12:00", "message": "Trying out Elasticsearch, so far so good?" }' curl -XPUT 'http://localhost:9200/twitter/doc/2?pretty' -H 'Content-Type: application/json' -d ' { "user": "kimchy", "post_date": "2009-11-15T14:12:12", "message": "Another tweet, will it be indexed?" }' curl -XPUT 'http://localhost:9200/twitter/doc/3?pretty' -H 'Content-Type: application/json' -d ' { "user": "elastic", "post_date": "2010-01-15T01:46:38", "message": "Building the site, should be kewl" }'
Now, let’s see if the information was added by GETting it:
curl -XGET 'http://localhost:9200/twitter/doc/1?pretty=true' curl -XGET 'http://localhost:9200/twitter/doc/2?pretty=true' curl -XGET 'http://localhost:9200/twitter/doc/3?pretty=true'
Mmm search…, shouldn’t it be elastic?
Let’s find all the tweets that kimchy
posted:
curl -XGET 'http://localhost:9200/twitter/_search?q=user:kimchy&pretty=true'
We can also use the JSON query language Elasticsearch provides instead of a query string:
curl -XGET 'http://localhost:9200/twitter/_search?pretty=true' -H 'Content-Type: application/json' -d ' { "query" : { "match" : { "user": "kimchy" } } }'
Just for kicks, let’s get all the documents stored (we should see the tweet from elastic
as well):
curl -XGET 'http://localhost:9200/twitter/_search?pretty=true' -H 'Content-Type: application/json' -d ' { "query" : { "match_all" : {} } }'
We can also do range search (the post_date
was automatically identified as date)
curl -XGET 'http://localhost:9200/twitter/_search?pretty=true' -H 'Content-Type: application/json' -d ' { "query" : { "range" : { "post_date" : { "from" : "2009-11-15T13:00:00", "to" : "2009-11-15T14:00:00" } } } }'
There are many more options to perform search, after all, it’s a search product no? All the familiar Lucene queries are available through the JSON query language, or through the query parser.
Man, that twitter index might get big (in this case, index size == valuation). Let’s see if we can structure our twitter system a bit differently in order to support such large amounts of data.
Elasticsearch supports multiple indices. In the previous example we used an index called twitter
that stored tweets for every user.
Another way to define our simple twitter system is to have a different index per user (note, though that each index has an overhead). Here is the indexing curl’s in this case:
curl -XPUT 'http://localhost:9200/kimchy/doc/1?pretty' -H 'Content-Type: application/json' -d ' { "user": "kimchy", "post_date": "2009-11-15T13:12:00", "message": "Trying out Elasticsearch, so far so good?" }' curl -XPUT 'http://localhost:9200/kimchy/doc/2?pretty' -H 'Content-Type: application/json' -d ' { "user": "kimchy", "post_date": "2009-11-15T14:12:12", "message": "Another tweet, will it be indexed?" }'
The above will index information into the kimchy
index. Each user will get their own special index.
Complete control on the index level is allowed. As an example, in the above case, we would want to change from the default 5 shards with 1 replica per index, to only 1 shard with 1 replica per index (== per twitter user). Here is how this can be done (the configuration can be in yaml as well):
curl -XPUT http://localhost:9200/another_user?pretty -H 'Content-Type: application/json' -d ' { "index" : { "number_of_shards" : 1, "number_of_replicas" : 1 } }'
Search (and similar operations) are multi index aware. This means that we can easily search on more than one
index (twitter user), for example:
curl -XGET 'http://localhost:9200/kimchy,another_user/_search?pretty=true' -H 'Content-Type: application/json' -d ' { "query" : { "match_all" : {} } }'
Or on all the indices:
curl -XGET 'http://localhost:9200/_search?pretty=true' -H 'Content-Type: application/json' -d ' { "query" : { "match_all" : {} } }'
{One liner teaser}: And the cool part about that? You can easily search on multiple twitter users (indices), with different boost levels per user (index), making social search so much simpler (results from my friends rank higher than results from friends of my friends).
Let’s face it, things will fail….
Elasticsearch is a highly available and distributed search engine. Each index is broken down into shards, and each shard can have one or more replica. By default, an index is created with 5 shards and 1 replica per shard (5/1). There are many topologies that can be used, including 1/10 (improve search performance), or 20/1 (improve indexing performance, with search executed in a map reduce fashion across shards).
In order to play with the distributed nature of Elasticsearch, simply bring more nodes up and shut down nodes. The system will continue to serve requests (make sure you use the correct http port) with the latest data indexed.
We have just covered a very small portion of what Elasticsearch is all about. For more information, please refer to the elastic.co website. General questions can be asked on the Elastic Discourse forum or on IRC on Freenode at #elasticsearch. The Elasticsearch GitHub repository is reserved for bug reports and feature requests only.
Elasticsearch uses Gradle for its build system. You’ll need to have at least version 3.3 of Gradle installed.
In order to create a distribution, simply run the gradle assemble
command in the cloned directory.
The distribution for each project will be created under the build/distributions
directory in that project.
See the TESTING file for more information about running the Elasticsearch test suite.
In order to ensure a smooth upgrade process from earlier versions of
Elasticsearch (1.x), it is required to perform a full cluster restart. Please
see the “setup reference”:
https://www.elastic.co/guide/en/elasticsearch/reference/current/setup-upgrade.html
for more details on the upgrade process.
This software is licensed under the Apache License, version 2 ("ALv2"), quoted below. Copyright 2009-2016 Elasticsearch <https://www.elastic.co> Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
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