Add NULL checks to prevent segfaults when Kafka metadata contains NULL

[k-raina]

Problem

Application crashes with segmentation fault when calling AdminClient.describeTopics() during Kafka broker restarts. The crash occurs when converting node metadata to JavaScript objects.

Root Cause: During broker restarts, Kafka metadata can contain NULL node pointers or NULL host fields. The code dereferenced these NULL pointers without checks, causing segfaults.

Replication steps

• Docker Compose environment: Start 3 Kafka brokers + ZooKeeper
• Start Client which continuously calls describeTopics() every 500ms on 10 test topics
• Run Chaos scripts ( like restart-brokers.sh) to trigger broker restarts/kills
• During restarts: Kafka sends metadata updates with changing node information
• When brokers go offline: node structures have NULL host fields
• Native code converts nodes to JavaScript without NULL checks → segfault

Solution

Added defensive NULL checks in two functions:

1. ToV8Object() - Check if node pointer and host field are NULL before accessing
2. FromDescribeTopicsResult() - Check leader, ISR, and replica nodes for NULL before conversion

NULL values are now safely converted to JavaScript null instead of crashing.

Testing

Without Fix

➜  JavaScript_1_3_1_SEG_Fault_Repro-Modifie-2 cat client/logs/stderr.log
=========== Caught a Segmentation Fault [pid=76203] ===========
-----[ Native Stacktraces ]-----
Cannot unwind stacktraces: Feature disabled / Missing libunwind on your system

---[ V8 JavaScript Stacktraces ]---
============================================================

With Fix

  ➜  JavaScript_1_3_1_SEG_Fault_Repro-Modifie-2 cat client/logs/stderr.log
➜  JavaScript_1_3_1_SEG_Fault_Repro-Modifie-2 

No segfault noticed

[Copilot]

Pull request overview

Adds NULL pointer checks to prevent segmentation faults when Kafka metadata contains NULL values during broker restarts or metadata updates.

• Adds NULL checks for node pointers and host fields in ToV8Object()
• Adds NULL checks for leader, ISR, and replica nodes in FromDescribeTopicsResult()
• Fixes memory leaks by destroying partition lists when validation fails

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The logic extracts a 'timestamp' parameter from the offset object but assigns it to toppar->offset. This is confusing - if the parameter name is 'timestamp', consider renaming the local variable to timestamp for clarity, or verify that 'timestamp' is the correct parameter name to extract.