CODEWITHSUNDEEP
javaluceneelasticsearch
krinker
krinker

Reputation: 1092

ElasticSeach JAVA API to find aliases given index

How to find aliases for given index in ElasticSearch using Java?

By using REST API it is pretty easy

https://www.elastic.co/guide/en/elasticsearch/reference/1.x/indices-aliases.html#alias-retrieving

But I was unable to find any good reference on how to do it via Java API

Upvotes: 2

Views: 1394

Answers (2)

gil.fernandes
gil.fernandes

Reputation: 14611

The previous answer is OK for ElasticSearch 2.x. Things have changed slightly in version 5.x of ElasticSearch though.

This is what has worked for me for version 5.x:

public Collection<String> findAliasForIndices(String... indices) {
    if(indices == null || indices.length == 0) {
        return Collections.emptyList();
    }
    ClusterStateRequest clusterStateRequest = Requests.clusterStateRequest()
            .routingTable(false)
            .nodes(false)
            .indices(indices);

    ImmutableOpenMap<String, IndexMetaData> aliasMap = client
            .admin().cluster().state(clusterStateRequest)
            .actionGet().getState().getMetaData()
            .getIndices();

    return StreamSupport.stream(aliasMap.spliterator(), false).flatMap((e) -> {
        Iterable<String> iterable = () -> e.value.getAliases().keysIt();
        return StreamSupport.stream(iterable.spliterator(), false);
    }).collect(Collectors.toSet());
}

This method returns all the aliases as strings for a collection of indices.

Usage example with JUnit and AssertJ:

@Test
public void whenFindAliasForIndices_ShouldRetrieveIndices() throws IOException {
    String testIndex = "blah1";
    String alias1 = "alias1";
    createIndexWithAlias(testIndex, alias1);

    String testIndex2 = "blah2";
    String alias2 = "alias2";
    createIndexWithAlias(testIndex2, alias2);

    Collection<String> indices = adapter.findAliasForIndices(testIndex, testIndex2);
    assertThat(indices.contains(alias1)).isTrue();
    assertThat(indices.contains(alias2)).isTrue();
    adapter.deleteIndices(testIndex);
    adapter.deleteIndices(testIndex2);
}

Upvotes: 0

krinker
krinker

Reputation: 1092

While working with ElasticSearch, I ran into an issue where I needed to get a list of aliases based on provided index.

While getting a list of aliases is pretty straightforward:

 client.admin().cluster()
    .prepareState().execute()
    .actionGet().getState()
    .getMetaData().aliases();

I struggled to find an easy way to be able to get aliases for given index without having to iterate through everything first.

My first implementation looked something like this:

    ImmutableOpenMap<String, ImmutableOpenMap<String, AliasMetaData>> aliases = client.admin().cluster()
        .prepareState().execute()
        .actionGet().getState()
        .getMetaData().aliases();

    for (ObjectCursor<String> key: aliases.keys()) {
        ImmutableOpenMap<String, AliasMetaData> indexToAliasesMap = client.admin().cluster()
          .state(Requests.clusterStateRequest())
          .actionGet().getState()
          .getMetaData().aliases().get(key.value);

        if(indexToAliasesMap != null && !indexToAliasesMap.isEmpty()){
            String index= indexToAliasesMap.keys().iterator().next().value;
            String alias = indexToAliasesMap.values().iterator().next().value.alias();
        }
    }

I did not like it... and after poking around, I was able to get an idea on how to do it more efficiently by looking at RestGetIndicesAliasesAction (package org.elasticsearch.rest.action.admin.indices.alias.get)

This is what I end up with:

    ClusterStateRequest clusterStateRequest = Requests.clusterStateRequest()
            .routingTable(false)
            .nodes(false)
            .indices("your_index_name_goes_here");

    ObjectLookupContainer<String> setAliases= client
            .admin().cluster().state(clusterStateRequest)
            .actionGet().getState().getMetaData()
            .aliases().keys();

You will be able to find aliases for the index that you specified in setAliases

Hope it helps someone!

Upvotes: 3

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