Attempting to trigger G1GC due to high heap usage – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-2.9

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Briefly, this error occurs when OpenSearch is trying to trigger the Garbage First Garbage Collector (G1GC) due to high heap usage. This means that the JVM heap space is almost full, which can lead to performance issues or even crashes. To resolve this issue, you can increase the heap size if your server has enough memory. Alternatively, you can optimize your queries or indices to reduce memory usage. Also, consider checking for memory leaks in your application or using a tool to analyze heap usage.

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This guide will help you check for common problems that cause the log ” attempting to trigger G1GC due to high heap usage [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: breaker, indices.

Log Context

Log “attempting to trigger G1GC due to high heap usage [{}]” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                    long begin = timeSupplier.getAsLong();
                    leader = begin >= lastCheckTime + minimumInterval;
                    if (leader) {
                        long initialCollectionCount = gcCountSupplier.getAsLong();
              "attempting to trigger G1GC due to high heap usage [{}]"; memoryUsed.baseUsage);
                        long localBlackHole = 0;
                        // number of allocations; corresponding to (approximately) number of free regions + 1
                        int allocationCount = Math.toIntExact((maxHeap - memoryUsed.baseUsage) / g1RegionSize + 1);
                        // allocations of half-region size becomes single humongous alloc; thus taking up a full region.
                        int allocationSize = (int) (g1RegionSize >> 1);


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