=== Talking to Elasticsearch
How you talk to Elasticsearch depends on((("Elasticsearch", "talking to"))) whether you are using Java.
==== Java API
If you are using ((("Java", "clients for Elasticsearch")))Java, Elasticsearch comes with two built-in clients that you can use in your code:
Node client:: The node client ((("node client")))joins a local cluster as a non data node. In other words, it doesn't hold any data itself, but it knows what data lives on which node in the cluster, and can forward requests directly to the correct node.
Transport client:: The lighter-weight ((("transport client")))transport client can be used to send requests to a remote cluster. It doesn't join the cluster itself, but simply forwards requests to a node in the cluster.
Both Java clients talk to the cluster over port 9300, using((("port 9300 for Java clients"))) the native Elasticsearch transport protocol. The nodes in the cluster also communicate with each other over port 9300. If this port is not open, your nodes will not be able to form a cluster.
[TIP]
The Java client must be from the same version of Elasticsearch as the nodes;
otherwise, they may not be able to understand each other.
More information about the Java clients can be found in the Java API section of the http://www.elasticsearch.org/guide/[Guide].
==== RESTful API with JSON over HTTP
All other languages can communicate with Elasticsearch((("port 9200 for non-Java clients"))) over port 9200 using
a ((("RESTful API, communicating with Elasticseach")))RESTful API, accessible with your favorite web client. In fact, as you have
seen, you can even talk to Elasticsearch from the command line by using the
curl command.((("curl command", "talking to Elasticsearch with")))
NOTE: Elasticsearch provides official clients((("clients", "other than Java"))) for several languages--Groovy, JavaScript, .NET, PHP, Perl, Python, and Ruby--and there are numerous community-provided clients and integrations, all of which can be found in the http://www.elasticsearch.org/guide/[Guide].
A request to Elasticsearch consists of the same parts as any HTTP request:((("HTTP requests")))((("requests to Elasticsearch")))
[source,js]
curl -X ':///?' -d ''
The parts marked with < > above are:
[horizontal]
VERB:: The appropriate HTTP method or verb: GET, POST, PUT, HEAD, or DELETE.
PROTOCOL:: Either http or https (if you have an https proxy in front of Elasticsearch.)
HOST:: The hostname of any node in your Elasticsearch cluster, or +localhost+ for a node on your local machine.
PORT:: The port running the Elasticsearch HTTP service, which defaults to 9200.
QUERY_STRING:: Any optional query-string parameters (for example ?pretty will pretty-print the JSON response to make it easier to read.)
BODY:: A JSON-encoded request body (if the request needs one.)
For instance, to count the number of documents in the cluster, we could use this:
[source,js]
curl -XGET 'http://localhost:9200/_count?pretty' -d ' { "query": { "match_all": {} } }
'
Elasticsearch returns an HTTP status code like 200 OK and (except for HEAD
requests) a JSON-encoded response body. The preceding curl request would respond
with a JSON body like the following:
[source,js]
{ "count" : 0, "_shards" : { "total" : 5, "successful" : 5, "failed" : 0 }
}
We don't see the HTTP headers in the response because we didn't ask curl to
display them. To see the headers, use the curl command with the -i
switch:
[source,js]
curl -i -XGET 'localhost:9200/'
For the rest of the book, we will show these curl examples using a shorthand
format that leaves out all the bits that are the same in every request,
like the hostname and port, and the curl command itself. Instead of showing
a full request like
[source,js]
curl -XGET 'localhost:9200/_count?pretty' -d ' { "query": { "match_all": {} }
}'
we will show it in this shorthand format:
[source,js]
GET /_count { "query": { "match_all": {} }
}
// SENSE: 010_Intro/15_Count.json
In fact, this is the same format that is used by the ((("Marvel", "Sense console")))((("Sense console (Marvel plugin)", "curl requests in")))Sense console that we
installed with <