CassandraMetriccassandra_compaction_tasks_pending
Number of queued tasks in a thread pool waiting to be runDimensions:None
Interface Metrics (3)
Native
Number of queued tasks in a thread pool waiting to be run
Dimensions:None
Sources
Knowledge Base (10 documents, 0 chunks)
guideCritical Cassandra Performance Metrics to Monitor - Sematext2324 wordsscore: 0.95This comprehensive guide explains critical Cassandra performance metrics to monitor, covering node availability, compaction metrics, read/write performance, table-level metrics including partition size and tombstones, and cache utilization. It provides context on Cassandra architecture and explains why each metric category matters for cluster health and performance.
guideApache Cassandra Monitoring with OpenTelemetry [including dashboards and alerts] | SigNoz3733 wordsscore: 0.95Comprehensive guide on monitoring Apache Cassandra using OpenTelemetry for metrics collection. Covers the complete architecture from JMX metrics exposure to OTel Collector integration with SigNoz, and provides detailed explanations of critical production metrics including latency, compaction, storage, and JVM health indicators.
guideCompaction in Cassandra | Datavail1441 wordsscore: 0.65This guide explains Cassandra's compaction process, including different compaction strategies (STCS, LCS, DTCS, TWCS), tuning parameters, and performance impacts. It covers when to use each strategy and how to troubleshoot compaction-related performance issues like slow reads and node unreachability.
troubleshootingCassandra Node unable to compact - Stack Diagnosis489 wordsscore: 0.72This page provides troubleshooting guidance for Cassandra nodes unable to complete compaction due to resource constraints. It covers root causes like insufficient disk space, memory, and CPU, along with resolution steps including resource allocation adjustments, compaction strategy changes, and monitoring recommendations.
blog post|
Compaction Strategies, Performance, and Their Impact on Cassandra Node Density1766 wordsscore: 0.65This blog post examines how different compaction strategies in Apache Cassandra impact node density and cost efficiency. It covers the trade-offs of STCS, LCS, and TWCS, and advocates for the new UnifiedCompactionStrategy (UCS) in Cassandra 5.0 as a game-changer that combines benefits of previous strategies while maintaining controlled SSTable sizes.
troubleshootingbigdata - Cassandra low read performance with high SSTable count - Stack Overflow1958 wordsscore: 0.72A Stack Overflow question discussing Cassandra read performance issues related to high SSTable count. The discussion covers interpreting nodetool cfstats output, understanding SSTable distribution, and recommendations for compaction strategy selection (SizeTieredCompactionStrategy vs LeveledCompactionStrategy) to improve read performance.
troubleshootingKey Concepts: Cassandra Heap Issues666 wordsscore: 0.75This page provides troubleshooting guidance for Cassandra heap memory issues and Out Of Memory (OOM) exceptions. It explains common causes including memtables, read patterns, repair operations, and compactions, along with diagnostic approaches using nodetool commands and potential workarounds for heap pressure.
troubleshootingCassandra - Operation timed out | Dovecot Pro408 wordsscore: 0.72This troubleshooting guide addresses Cassandra 'Operation timed out' errors in Dovecot Pro environments, focusing on issues caused by excessive tombstones. It provides solutions including compaction strategies, configuration adjustments for tombstone thresholds and timeouts, and Cassandra paging implementation.
documentationCassandra Disk Usage Explained - Instaclustr283 wordsscore: 0.72This page explains Cassandra disk usage metrics and provides operational guidance for managing disk space on Cassandra nodes. It recommends maintaining disk usage below 70% during normal operations with a minimum of 30% free space to allow for compaction and other temporary operations.
best practicesWhat you should understand before using Apache Cassandra in production | Running Code606 wordsscore: 0.75This blog post explains Cassandra's storage architecture (memtables, SSTables, and compaction) and emphasizes a critical operational best practice: setting disk space alerts at 50% rather than the typical 80-90% threshold. This is because compaction requires approximately 50% free disk space to merge SSTables, and without compaction, disk space cannot be freed, creating an operational crisis.
Related Insights (6)
Compaction Backlog Causing Read Latency Cascadecritical
When pending compaction tasks accumulate faster than they can complete, reads must scan excessive SSTables, driving p99 latency upward and eventually causing timeout exceptions. This silent storage debt compounds over time.
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Tombstone Accumulation Slowing Read Pathwarning
Frequent deletes create tombstones that must be scanned during reads. When tombstone counts exceed 1000 per read, query latency degrades dramatically despite healthy system resources, often masking as a generic slow query problem.
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Disk Space Exhaustion from Snapshot Accumulationcritical
Old snapshots from backups or schema changes accumulate on disk, silently consuming storage until reaching 90%+ capacity. This blocks compaction and eventually causes node failures with disk-full errors.
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Compaction Backlog Choking Read Performancewarning
When pending compaction tasks accumulate, read latency degrades because queries must scan many SSTables. This manifests as rising P99 read latency while write latency remains stable, often accompanied by increasing SSTables-per-read counts.
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Compaction Strategy Mismatch Degrading Node Densitywarning
Using STCS (Size-Tiered) creates unbounded SSTable growth and prevents fast streaming, while LCS (Leveled) causes excessive write amplification under heavy load. Both reduce effective node density and operational efficiency compared to UCS (Unified) in Cassandra 5.0+.
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Unified Compaction Strategy consolidates compaction strategieswarning
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