https://github.com/canack/nats-header-problem
The example code that gives panic
https://github.com/canack/nats-header-problem
Last synced: about 2 months ago
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The example code that gives panic
- Host: GitHub
- URL: https://github.com/canack/nats-header-problem
- Owner: canack
- Created: 2024-10-02T20:05:48.000Z (8 months ago)
- Default Branch: master
- Last Pushed: 2024-10-02T20:10:06.000Z (8 months ago)
- Last Synced: 2024-11-21T05:37:09.153Z (6 months ago)
- Language: Go
- Size: 4.88 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# NATS Go Client Header Bug Demonstration
This repository demonstrates a bug in the NATS Go client where setting headers on messages that initially lack them causes a panic.
## Overview
In NATS, messages can have headers for storing metadata. The issue occurs when a consumer attempts to add or modify headers on a message that originally does not have any headers, leading to an application crash.
## Problem Description
### Steps to Reproduce
1. **Producer**: Sends messages to a NATS subject.
- The first three messages include a "Publish-Count" header.
- Subsequent messages do not include any headers.
2. **Consumer**: Receives messages and attempts to set a new header "No-Panic":
- If the message already has headers, the operation succeeds.
- If the message has no headers, the operation causes a panic due to the lack of header initialization.
### Illustration
```plaintext
Scenario 1: Message with Initial Headers
+-----------------+ +--------------------+
| Producer | Send Message | Consumer |
| (with headers) |---------------------->| Reads Headers |
+-----------------+ | Set/Add Header |
| (success) |
+--------------------+
Scenario 2: Message without Initial Headers
+-----------------+ +--------------------+
| Producer | Send Message | Consumer |
| (no headers) |---------------------->| Attempt Set/Add |
+-----------------+ | Header (panic!) |
+--------------------+
```
## Solution
To fix this issue, ensure that the consumer checks if the message contains headers before setting new ones. If not, initialize the header map to prevent a panic and maintain application stability.
### The related PR : https://github.com/nats-io/nats.go/pull/1724