Skip to content

Blog

Production error deep-dives — root cause, reproduction, and the fix that holds.

HeapDumpOnOutOfMemoryError: Production Setup That Works

HeapDumpOnOutOfMemoryError is useless if the dump lands on a full disk or vanishes with the pod. How I set heap dumps up for production, containers included.

Java OutOfMemoryError: Every Message and What It Means

Java heap space, Metaspace, GC overhead, direct buffer, native thread: every OutOfMemoryError message, the memory area behind it, and where to look first.

Flink: Could Not Find Any Factory for Identifier 'kafka'

Flink throws ValidationException: Could not find any factory for identifier 'kafka' in the classpath. Here is why SPI discovery fails and how to fix it.

ExitOnOutOfMemoryError: Why Your JVM Should Fail Fast

ExitOnOutOfMemoryError turns a half-dead JVM into a clean restart. What it catches, what it misses (threads, direct buffers), and how it ranks against CrashOn.

NoClassDefFoundError vs ClassNotFoundException in Java

NoClassDefFoundError and ClassNotFoundException look interchangeable and are not. Read the frames, find the real cause, and stop the repeat throws.

Flink: Cannot Map Savepoint State for Operator — Fix It

Flink's "Cannot map checkpoint/savepoint state for operator to the new program" error breaks upgrades. Here's why it happens and how to fix it with stable uid().

Flink Checkpoint Expired Before Completing: Causes & Fixes

Fix the Apache Flink 'Checkpoint expired before completing' error. Learn why checkpoints time out under backpressure and large state, and the exact config to stop it.

Flink NoResourceAvailableException: Could Not Acquire Minimum Resources

Fix Flink's NoResourceAvailableException 'Could not acquire the minimum required resources' — slot arithmetic, slot sharing, and the config that actually solves it.

Java NullPointerException: Cannot invoke ... because ... is null

Decode the helpful NullPointerException message — Cannot invoke "String.length()" because "s" is null — find the exact null reference, and fix it for good.

Java ConcurrentModificationException: Causes and Fixes

ConcurrentModificationException usually has nothing to do with threads. Here is exactly what modCount does, why it fires, and the four fixes that actually work.