apache/cassandra · warning

<garbage collection summary>

Error message

<garbage collection summary>

What it means

A WARN/INFO/TRACE log (not an exception) from GCInspector.handleNotification for a GarbageCollectionNotificationInfo whose GC is a concurrent phase (e.g. G1 concurrent mark/cleanup). The '<garbage collection summary>' string is the formatted GC statistics built into sb. It is logged at WARN when the duration exceeds the concurrent-phase warn threshold (gc_concurrent_phase_warn_threshold_in_ms), INFO above the log threshold, TRACE otherwise, and additionally dumps a StatusLogger status when the duration exceeds the concurrent status threshold (default 200ms).

Source

Thrown at src/java/org/apache/cassandra/service/GCInspector.java:331

                    sb.append(" -> ");
                    sb.append(after.getUsed());
                    if (!key.equals(gcState.keys[gcState.keys.length - 1]))
                        sb.append("; ");
                    bytes += before.getUsed() - after.getUsed();
                }
            }

            while (true)
            {
                State prev = state.get();
                if (state.compareAndSet(prev, new State(duration, bytes, prev)))
                    break;
            }

            if (isConcurrentPhase(info.getGcCause(), info.getGcName()))
            {
                if (getGcConcurrentPhaseWarnThresholdInMs() != 0 && duration > getGcConcurrentPhaseWarnThresholdInMs())
                    logger.warn(sb.toString());
                else if (duration > getGcConcurrentPhaseLogThresholdInMs())
                    logger.info(sb.toString());
                else if (logger.isTraceEnabled())
                    logger.trace(sb.toString());

                if (duration > this.getConcurrentStatusThresholdInMs())
                    StatusLogger.log();
            }
            else
            {
                if (getGcWarnThresholdInMs() != 0 && duration > getGcWarnThresholdInMs())
                    logger.warn(sb.toString());
                else if (duration > getGcLogThresholdInMs())
                    logger.info(sb.toString());
                else if (logger.isTraceEnabled())
                    logger.trace(sb.toString());

                if (duration > this.getStatusThresholdInMs())

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Inspect the log line and StatusLogger output to identify which concurrent phase is slow and the heap usage before/after
2. Tune GC via jvm11-server.options (e.g. increase heap, adjust G1 heap region size, InitiatingHeapOccupancyPercent, GC threads) or via -Dcassandra.gc_concurrent_phase_warn_threshold_ms if thresholds are too aggressive
3. If pauses cause coordinator timeouts, investigate memory pressure (huge partitions, memtable sizing) driving long concurrent cycles

Example fix

// before (jvm-server.options)
-Xms8G -Xmx8G

// after
-Xms31G -Xmx31G  # reduce concurrent-cycle frequency on large nodes
// or relax threshold:
-Dcassandra.gc_concurrent_phase_warn_threshold_ms=1000

// Threshold sanity check before deploy (gc_concurrent_phase_warn_threshold_in_ms)
long warnMs = Long.getLong("cassandra.gc_concurrent_phase_warn_threshold_ms", 500);
if (warnMs <= 0) System.out.println("Concurrent-phase GC warning disabled; long concurrent cycles will be silent");

When it happens

Trigger: JVM GC bean notification for a concurrent collection phase whose duration exceeds getGcConcurrentPhaseWarnThresholdInMs() (WARN), getGcConcurrentPhaseLogThresholdInMs() (INFO), or any duration with trace logging enabled; StatusLogger fires when duration > getConcurrentStatusThresholdInMs().

Common situations: Large heaps with G1/ZGC/CMS concurrent cycles taking hundreds of ms; undersized heap or too few GC threads; heavy write load causing long concurrent mark cycles; operators investigating latency spikes.

Understand the failure class

Background: Request timed out: what client-side request timeouts mean across libraries (Request timed out, TIMED_OUT, APITimeoutError) — this error's family across 39 libraries.

Related errors

• 32bit JVM detected. It is recommended to run Cassandra on a
• Access is denied!
• Threshold value for gc_log*_threshold must be greater than 0
• Threshold value for gc_warn*_threshold must be greater than
• Threshold value for gc_log*_threshold (%d) must be less than

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/dbfe0ebc54d4d00f. Report an issue: GitHub.