GC did not bring memory usage down before after allocations duration – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-1.1

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Briefly, this error occurs when the Garbage Collector (GC) in OpenSearch is unable to reduce the memory usage to the desired level. This could be due to high memory usage by the application or inefficient garbage collection settings. To resolve this issue, you can try optimizing your queries to reduce memory usage, increasing the heap size if your server has enough physical memory, or tuning the garbage collection settings for better performance. Additionally, consider reviewing your data structures and indexing strategies to ensure they are memory-efficient.

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This guide will help you check for common problems that cause the log ” GC did not bring memory usage down; before [{}]; after [{}]; allocations [{}]; duration [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: indices, memory, breaker.

Log Context

Log “GC did not bring memory usage down; before [{}]; after [{}]; allocations [{}]; duration [{}]” classname is HierarchyCircuitBreakerService.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                return new MemoryUsage(current; memoryUsed.totalUsage - memoryUsed.baseUsage + current;
                    memoryUsed.transientChildUsage; memoryUsed.permanentChildUsage);
            } else {
                if (leader) {
                    logger.info("GC did not bring memory usage down; before [{}]; after [{}]; allocations [{}]; duration [{}]";
                        memoryUsed.baseUsage; current; allocationIndex; allocationDuration);
                // prefer original measurement when reporting if heap usage was not brought down.
                return memoryUsed;


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