I have got the error log below, anyone may help?
[2018-01-11T15:50:37,742][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [node-2] fatal error in thread [elasticsearch[node-2][search][T#1]], exiting
java.lang.OutOfMemoryError: Java heap space
at org.apache.lucene.util.packed.Direct8.(Direct8.java:36) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.util.packed.PackedInts.getMutable(PackedInts.java:954) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.util.packed.PackedInts.getMutable(PackedInts.java:939) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.util.packed.GrowableWriter.(GrowableWriter.java:46) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.util.packed.PagedGrowableWriter.newMutable(PagedGrowableWriter.java:56) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.util.packed.AbstractPagedMutable.fillPages(AbstractPagedMutable.java:57) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.util.packed.PagedGrowableWriter.(PagedGrowableWriter.java:50) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.util.packed.PagedGrowableWriter.(PagedGrowableWriter.java:43) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.elasticsearch.index.fielddata.ordinals.OrdinalsBuilder$OrdinalsStore.(OrdinalsBuilder.java:163) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.index.fielddata.ordinals.OrdinalsBuilder.(OrdinalsBuilder.java:291) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.index.fielddata.plain.PagedBytesIndexFieldData.loadDirect(PagedBytesIndexFieldData.java:114) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.index.fielddata.plain.PagedBytesIndexFieldData.loadDirect(PagedBytesIndexFieldData.java:55) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.indices.fielddata.cache.IndicesFieldDataCache$IndexFieldCache.lambda$load$0(IndicesFieldDataCache.java:135) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.indices.fielddata.cache.IndicesFieldDataCache$IndexFieldCache$$Lambda$1958/336390819.load(Unknown Source) ~[?:?]
at org.elasticsearch.common.cache.Cache.computeIfAbsent(Cache.java:401) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.indices.fielddata.cache.IndicesFieldDataCache$IndexFieldCache.load(IndicesFieldDataCache.java:130) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.index.fielddata.plain.AbstractIndexFieldData.load(AbstractIndexFieldData.java:68) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.index.fielddata.fieldcomparator.BytesRefFieldComparatorSource$1.getSortedDocValues(BytesRefFieldComparatorSource.java:92) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.apache.lucene.search.FieldComparator$TermOrdValComparator.getLeafComparator(FieldComparator.java:767) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.search.FieldValueHitQueue.getComparators(FieldValueHitQueue.java:180) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.search.TopFieldCollector$PagingFieldCollector.getLeafCollector(TopFieldCollector.java:191) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.search.FilterCollector.getLeafCollector(FilterCollector.java:40) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.elasticsearch.search.query.CancellableCollector.getLeafCollector(CancellableCollector.java:61) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:660) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:473) ~[lucene-core-6.5.1.jar:6.5.1 cd1f23c63abe03ae650c75ec8ccb37762806cc75 - jimczi - 2017-04-21 12:17:15]
at org.elasticsearch.search.query.QueryPhase.execute(QueryPhase.java:388) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.search.query.QueryPhase.execute(QueryPhase.java:108) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.search.SearchService.loadOrExecuteQueryPhase(SearchService.java:247) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.search.SearchService.executeQueryPhase(SearchService.java:262) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.action.search.SearchTransportService$6.messageReceived(SearchTransportService.java:339) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.action.search.SearchTransportService$6.messageReceived(SearchTransportService.java:336) ~[elasticsearch-5.4.1.jar:5.4.1]
at org.elasticsearch.transport.RequestHandlerRegistry.processMessageReceived(RequestHandlerRegistry.java:69) ~[elasticsearch-5.4.1.jar:5.4.1]
OS is CentOS 6.8 64bit, jdk is 1.8