Get Alias API

Get Alias Request

The Get Alias API uses GetAliasesRequest as its request object. One or more aliases can be optionally provided either at construction time or later on through the relevant setter method.

GetAliasesRequest request = new GetAliasesRequest();
GetAliasesRequest requestWithAlias = new GetAliasesRequest("alias1");
GetAliasesRequest requestWithAliases =
        new GetAliasesRequest(new String[]{"alias1", "alias2"});

Optional arguments

The following arguments can optionally be provided:

request.aliases("alias"); 

One or more aliases to retrieve

request.indices("index"); 

The index or indices that the alias is associated with

request.indicesOptions(IndicesOptions.lenientExpandOpen()); 

Setting IndicesOptions controls how unavailable indices are resolved and how wildcard expressions are expanded when looking for aliases that belong to specified indices.

request.local(true); 

The local flag (defaults to false) controls whether the aliases need to be looked up in the local cluster state or in the cluster state held by the elected master node

Synchronous Execution

When executing a GetAliasesRequest in the following manner, the client waits for the GetAliasesResponse to be returned before continuing with code execution:

GetAliasesResponse response = client.indices().getAlias(request, RequestOptions.DEFAULT);

Synchronous calls may throw an IOException in case of either failing to parse the REST response in the high-level REST client, the request times out or similar cases where there is no response coming back from the server.

In cases where the server returns a 4xx or 5xx error code, the high-level client tries to parse the response body error details instead and then throws a generic ElasticsearchException and adds the original ResponseException as a suppressed exception to it.

Asynchronous Execution

Executing a GetAliasesRequest can also be done in an asynchronous fashion so that the client can return directly. Users need to specify how the response or potential failures will be handled by passing the request and a listener to the asynchronous get-alias method:

client.indices().getAliasAsync(request, RequestOptions.DEFAULT, listener); 

The GetAliasesRequest to execute and the ActionListener to use when the execution completes

The asynchronous method does not block and returns immediately. Once it is completed the ActionListener is called back using the onResponse method if the execution successfully completed or using the onFailure method if it failed. Failure scenarios and expected exceptions are the same as in the synchronous execution case.

A typical listener for get-alias looks like:

ActionListener<GetAliasesResponse> listener =
        new ActionListener<GetAliasesResponse>() {
            @Override
            public void onResponse(GetAliasesResponse getAliasesResponse) {
                
            }

            @Override
            public void onFailure(Exception e) {
                
            }
};

Called when the execution is successfully completed.

Called when the whole GetAliasesRequest fails.

Get Alias Response

The returned GetAliasesResponse allows to retrieve information about the executed operation as follows:

Map<String, Set<AliasMetaData>> aliases = response.getAliases(); 

Retrieves a map of indices and their aliases