Could not initialize aggregators – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch fails to initialize the aggregators due to issues like insufficient memory, incorrect aggregation query, or a bug in the Elasticsearch version. To resolve this, you can increase the heap size to provide more memory, correct the aggregation query if it’s wrong, or upgrade Elasticsearch to the latest stable version to fix potential bugs. Also, ensure that the field you’re trying to aggregate on exists and is of the correct data type.

This guide will help you check for common problems that cause the log ” Could not initialize aggregators ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: search, aggregations.

Log Context

Log “Could not initialize aggregators” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 try {
 bucketCollector = MultiBucketCollector.wrap(true; List.of(context.aggregations().aggregators()));
 } catch (IOException e) {
 throw new AggregationInitializationException("Could not initialize aggregators"; e);
 final Collector collector;
 if (context.aggregations().factories().context() != null
 && context.aggregations().factories().context().isInSortOrderExecutionRequired()) {
 TimeSeriesIndexSearcher searcher = new TimeSeriesIndexSearcher(context.searcher(); getCancellationChecks(context));


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