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Memory Mapped Stats Tools
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Documentation | Package | Code

Not under active development


Mmstats is a way to expose and read diagnostic values and metrics for applications.

Think of mmstats as /proc for your application and the readers as procps utilities.

This project is a Python implementation, but compatible implementations can be made in any language (see Goals).

Discuss at


  • Separate publishing/writing from consuming/reading tools
  • Platform/language independent (a Java writer can be read by a Python tool)
  • Predictable performance impact for writers via:
    • No locks (1 writer per thread)
    • No syscalls (after instantiation)
    • All in userspace
    • Reading has no impact on writers
  • Optional persistent (writer can sync anytime)
  • 1-way (Publish/consume only; mmstats are not management extensions)



CPython 2.6 or 2.7 (Windows is untested)

PyPy (only tested in 1.7, should be faster in 1.8)


  1. easy_install mmstats or pip install mmstats or if you've downloaded the source: python install
  2. Then in your Python project create a sublcass of mmstats.MmStats like
import mmstats

class WebStats(mmstats.MmStats):
    status2xx = mmstats.CounterField(label='status.2XX')
    status3xx = mmstats.CounterField(label='status.3XX')
    status4xx = mmstats.CounterField(label='status.4XX')
    status5xx = mmstats.CounterField(label='status.5XX')
    last_hit = mmstats.DoubleField(label='timers.last_hit')
  1. Instantiate it once per process: (instances are automatically thread local)
webstats = WebStats(label_prefix='web.stats.')
  1. Record some data:
if response.status_code == 200:

webstats.last_hit = time.time()
  1. Run slurpstats to read it
  2. Run mmash to create a web interface for stats
  3. Run pollstats -p web.stats.status 2XX,3XX,4XX,5XX /tmp/mmstats-* for a vmstat/dstat like view.
  4. Did a process die unexpectedly and leave around a stale mmstat file? cleanstats /path/to/mmstat/files will check to see which files are stale and remove them.
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