Resource Leaks: Files not closed properly in multiple modules

[Tech-Psycho95]

Summary

---

Some Nettacker modules use open().read() without context managers, which can leave file handles open and cause resource leaks. This can lead to exhaustion of file descriptors in long‑running processes.

Problem

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The following module contain unsafe file reads:

File	Fix Applied
nettacker/lib/html_log/log_data.py	HTML template reads
nettacker/lib/graph/d3_tree_v1/engine.py	D3 tree template read
nettacker/lib/compare_report/engine.py	Compare report template read

Resolution

Replace all bare open() calls with context managers:

# Before (unsafe)
content = open(filename).read()

# After (safe)
with open(filename) as f:
    content = f.read()

Testing

• Add new pytest tests under tests/lib/ to confirm:

• Files are read correctly.

• File handles are closed after reading.

• Edge cases (empty file, missing file) are handled properly.