In the previous recipe, we saw how to initialize a client to send calls to an Elasticsearch cluster. In this recipe, we will see how to manage indices via client calls.
You need an up-and-running Elasticsearch installation as we described in the Downloading and installing Elasticsearch recipe in Chapter 2, Downloading and Setup.
A Maven tool, or an IDE that natively supports it for Java programming such as Eclipse or IntelliJ IDEA, must be installed.
The code for this recipe is in the chapter_14/nativeclient directory and the referred class is IndicesOperations.
An Elasticsearch client maps all index operations under the admin.indices object of the client. All the indices operation are here (create, delete, exists, open, close, optimize, and so on).
The following code retrieves a client and executes the main operations on indices:
- We import the required classes:
import org.elasticsearch.action.admin.indices.exists.indices .IndicesExistsResponse; import org.elasticsearch.client.Client; - We define an
IndicesOperationsclass that manages the index operations:public class IndicesOperations { private final Client client; public IndicesOperations(Client client) { this.client = client; } - We define a function used to check the index's existence:
public boolean checkIndexExists(String name){ IndicesExistsResponse response=client.admin().indices().prepareExists(name).execute() .actionGet(); return response.isExists(); } - We define a function used to create an index:
public void createIndex(String name){ client.admin().indices().prepareCreate(name).execute() .actionGet(); } - We define a function used to delete an index:
public void deleteIndex(String name){ client.admin().indices().prepareDelete(name).execute() .actionGet(); } - We define a function used to close an index:
public void closeIndex(String name){ client.admin().indices().prepareClose(name).execute() .actionGet(); } - We define a function used to open an index:
public void openIndex(String name){ client.admin().indices().prepareOpen(name).execute() .actionGet(); } - We test all the previously defined functions:
public static void main( String[] args ) throws InterruptedException, IOException, NodeValidationException { NativeClient nativeClient=new NativeClient(); Client client =nativeClient.getClient(); IndicesOperations io=new IndicesOperations(client); String myIndex = "test"; if(io.checkIndexExists(myIndex)) io.deleteIndex(myIndex); io.createIndex(myIndex); Thread.sleep(1000); io.closeIndex(myIndex); io.openIndex(myIndex); io.deleteIndex(myIndex); //we need to close the client to free resources nativeClient.close(); }
Before executing every index operation, a client must be available (we saw how to create one in the previous recipe).
The client has a lot of methods grouped by functionalities:
- In the root
client.*we have record operations such as index, deletion of records, search, and update - Under
admin.indices.*we have index related methods, such as create index, delete index, and so on - Under
admin.cluster.*, we have cluster-related methods, such as state and health
Client methods usually follow some conventions:
- Methods starting with
prepare*(that isprepareCreate) returns a request builder that can be executed with theexecutemethod - Methods that starts with a verb (that is
create) require a build request and optional some action listener
After building the request, it can be executed with an actionGet that can receive an optional timeout, and a response is returned.
In the previous example, we have several index calls:
- Checking the existence, the method call is
prepareExistsand returns anIndicesExistsResponseobject, which contains information about whether the index exists or not:
IndicesExistsResponse
response=client.admin().indices().prepareExists(name).execute()
.actionGet();
return response.isExists();
- Creating an index, with the
prepareCreatecall:
client.admin().indices().prepareCreate(name).execute()
.actionGet();
- Closing an index, with the
prepareClosecall:
client.admin().indices().prepareClose(name).execute()
.actionGet();
- Opening an index, with the
prepareOpencall:
client.admin().indices().prepareOpen(name).execute()
.actionGet();
- Deleting an index with the
prepareDeletecall:
client.admin().indices().prepareDelete(name).execute()
.actionGet();
Note
We have put a delay of 1 second (Thread.wait(1000)) in the code to prevent fast actions on indices, because their shard allocations are asynchronous and they require some milliseconds to be ready. The best practice is not to use a similar hack, but to poll an index's state before perform further operations, and only performing those operations when it goes green.