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Browse 5 real-world technical and behavioral interview questions about Troubleshooting. Review scenarios, edge cases, and architectural best practices.
Most likely into reaching the safepoint. Every application thread has to arrive at a poll point before the operation can begin, and one late thread stalls all of them, so the pause is time-to-safepoint plus the actual work. Safepoint logging separates the two.
Work up the layers and let each command eliminate a class of cause: resolve the name, check the route, see whether anything is listening, then decide from the failure mode whether packets are being refused, silently dropped, or answered by something that never replies.
When a customer insists a product bug is actually their integration issue, investigate from a shared request ID, prove the boundary failure with reproducible evidence, and deliver the finding without embarrassing the customer engineer.
df and du disagree because df reads filesystem block allocation while du walks visible directory entries. Deleted-but-open files, inode exhaustion, hidden files under mounts and reserved blocks are the usual causes. Use this LINUX answer to show the decision, trade-off, and evidence rather than a memorised definition. It also connects filesystems to the point an interviewer is testing.
Read the message text first, because it names which region ran out. Then use the GC log to see whether the live set after each full collection is trending upward, which means a leak, or flat and close to the ceiling, which means the heap is simply too small. A heap dump tells you what is retaining the memory.