LmdbSessions: An LMDB Based Backend for CherryPy Sessions

LmdbSessions is an almost drag-and-drop substitute for CherryPy's built-in file backed sessions, but with much better performance, e.g. 6x faster reads and 3x faster writes.

Installation

Installation should be as easy as:

$ pip install lmdb_sessions

To install from source:

$ cd /path/to/lmdb_sessions && pip install . --upgrade

Usage

The script server.py in the examples directory demonstrates how to setup LmdbSessions on a CherryPy server and use it to show a user how many times they have visited the site.

To use, you first need to import the LmdbSession class:

from lmdb_sessions.sessions import LmdbSession

Then you have to configure your server to use LmdbSession based sessions:

cherrypy.config.update({
	'tools.sessions.on': True,
	'tools.sessions.storage_class': LmdbSession,
	'tools.sessions.storage_path': '/path/to/sessions/directory')
})

After that, usage should be exactly the same as any other CherryPy sessions backend, i.e. totally transparent.

Performance

You can compare the performance of LmdbSessions vs. CherryPy's built-in file based sessions yourself by running examples/perf.py. On my MacBook Pro, LmdbSessions performs reads roughly 6x faster and writes roughly 3x faster.

Backend Size

By Default, the LMDB session backend has a maximum size of 10MB; if you exceed this limit, new sessions will raise exceptions. You can increase the size limit of the backing store by adding the following config option:

cherrypy.config.update({
    'tools.sessions.map_size': map_size
})

Where map_size is the maximum size in bytes.