Midden

Midden is a tool for dumping and analysing heaps from Python programs.

It takes a "dump first, ask questions later" approach, making it easy to grab a heap dump from a running application, then analyse it offline later in its UI, potentially on a different machine entirely.

Installing

If you just want to grab a heap dump, you can install everything you need with:

pip install midden
# Or if you're using uv
uv add midden

If you want to analyse the data, you'll need the extra UI dependencies, which you can install with

pip install midden[ui]
# Or if you're using uv
uv add midden[ui]

Grabbing a Heap Dump

Grabbing a heap dump can be as simple as:

# Assuming pid we want to grab heap from is pid 12345
midden-inject 12345 --output-file /tmp/dump.jsonl

On Python 3.14 and newer, this will use sys.remote_exec, which means no extra dependencies. You will need appropriate permissions as documented here. Roughly speaking, you either need to be root/administrator, or be running on Linux with ptrace protection disabled.

On Python 3.10 to 3.13, injection is done with gdb, which means gdb needs to be installed. Gdb-based injection is only tested on Linux.

Analysing a Heap Dump

You can run the analysis UI with

midden-ui

This will start a web application, and pop up a web browser pointing at the analysis application. Upload a heap dump generated with midden-inject to get started.