Java

Guides

Guides overview 2 pages

Apache ZooKeeper Operations Guides

Practical guides for running, troubleshooting, and monitoring Apache ZooKeeper in production.

Cassandra Operations Guides

Practical guides for running, troubleshooting, and monitoring Apache Cassandra in production.

Cassandra Operations Guides 8 pages

Open the Cassandra Operations Guides hub

Cassandra GC death spiral: long pauses, gossip flapping, and recovery

Operational guide to identifying, diagnosing, and recovering from Cassandra GC death spirals caused by heap pressure, gossip timeouts, and hint replay floods.

Cassandra GC pauses too long: diagnosing G1 stop-the-world pauses

Diagnose and resolve long G1 stop-the-world pauses in Cassandra before they trigger gossip failures and client timeouts.

Cassandra gossip flapping: nodes bouncing UP and DOWN

Diagnose and stop Cassandra nodes flapping between UP and DOWN states caused by GC pressure, network issues, or gossip saturation.

Cassandra heap pressure: sizing the JVM heap and tuning G1GC

Size the JVM heap and tune G1GC for Cassandra 4.x and 5.x to avoid GC pauses, gossip flapping, and the death spiral.

Cassandra java.lang.OutOfMemoryError: Java heap space - causes and recovery

Diagnose and recover from Cassandra java.lang.OutOfMemoryError: Java heap space with heap sizing guidance, partition and batch analysis, and GC tuning.

Cassandra killed by the Linux OOM killer: off-heap memory and RSS

Diagnose and prevent Linux OOM kills on Cassandra nodes when off-heap RSS exceeds available RAM despite a healthy JVM heap.

Cassandra node showing DN in nodetool status: gossip, phi, and recovery

Diagnose why Cassandra nodes appear as DN in nodetool status, understand phi accrual failure detection, and recover from gossip flapping and network partitions.

Cassandra ReadTimeoutException: diagnosing coordinator read timeouts

Diagnose server-side Cassandra read timeouts where the coordinator fails to gather enough replica responses within read_request_timeout_in_ms.

Docker Operations Guides 2 pages

Open the Docker Operations Guides hub

Docker JVM memory tuning: heap, off-heap, and the cgroup mismatch

Diagnose why Java containers are OOMKilled despite healthy heap usage, fix JVM cgroup detection failures, and size heap and off-heap limits correctly.

Docker OOMKilled: causes, detection, and prevention

How to detect, diagnose, and prevent Docker OOMKilled events: confirming the kill, distinguishing it from SIGKILL, JVM memory pitfalls, and right-sizing limits.

Elasticsearch Operations Guides 3 pages

Open the Elasticsearch Operations Guides hub

Elasticsearch JVM heap usage high: reading the sawtooth and the post-GC floor

Diagnose Elasticsearch JVM heap pressure by reading the post-GC floor instead of the sawtooth peak. Identify shard, fielddata, and aggregation drivers before they trigger GC death spirals.

Elasticsearch long GC pauses: old-generation stop-the-world and node drops

Diagnose and fix Elasticsearch old-generation GC pauses that trigger stop-the-world events, fault-detection timeouts, and cascading node removals.

Elasticsearch node OOM-killed: heap ceiling, page cache, and container limits

Diagnose and fix Elasticsearch nodes killed by the Linux OOM-killer due to heap, off-heap, page cache, and container memory limit pressure.

Kafka Operations Guides 1 page

Open the Kafka Operations Guides hub

Kafka JVM heap and Full GC pauses: ISR drops, session timeouts, and right-sizing the heap

Diagnose and fix Kafka broker JVM heap pressure and Full GC pauses that trigger ISR shrinks, ZooKeeper session timeouts, and request latency spikes.

Apache ZooKeeper Operations Guides 4 pages

Open the Apache ZooKeeper Operations Guides hub

ZooKeeper "Client session timed out, have not heard from server": the heartbeat miss

Why the ZooKeeper client logs a session timeout heartbeat miss, what it means for the session, and how to isolate server GC, client GC, or network as the root cause.

ZooKeeper "Detected pause in JVM or host machine (eg GC)": the pause-monitor warning

Operator reference for ZooKeeper's JvmPauseMonitor warning: how to distinguish Stop-the-World GC from host-level freezes and which signals to correlate during recovery.

ZooKeeper KeeperErrorCode = Session expired: ephemeral nodes gone, clients evicted

Diagnose ZooKeeper session expiration, its cascading effects on ephemeral nodes and watches, and the GC, network, and failover causes behind mass client eviction.

ZooKeeper OutOfMemoryError: Java heap space - the OOM that kills the whole ensemble at once

Diagnose and stop the ZooKeeper Java heap space OOM that takes down an entire ensemble at once: data tree growth, GC death spiral, and heap sizing.

Academy

What Is A Memory Leak In Java How To Detect And Fix Them

An essential guide for developers to diagnose and resolve OutOfMemoryError issues in their applications

Garbage Collection In Java What It Is and How It Works

Understanding the automatic memory management that powers the JVM

Java Springboot Applications Monitoring

Learn everything you need to know about monitoring & troubleshooting Java Springboot Applications and use Netdata for effective management.

JMX Monitoring

Learn everything about monitoring & troubleshooting JMX, what metrics are important to monitor and why, and how to monitor JMX with Netdata.

Tomcat Monitoring

Learn everything about monitoring & troubleshooting Tomcat, what metrics are important to monitor and why, and how to monitor Tomcat with Netdata.

Resources

10 Best Apache Tomcat Monitoring Tools in 2026

We ranked the 10 best Apache Tomcat monitoring tools on JVM and JMX metric depth, setup time, data resolution, alerting, and total cost. See our picks.

Blog

Cassandra Monitoring: Key Metrics & Best Practices

Strategies For Ensuring Peak Performance & Stability