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
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!
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);
}
