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PSI - Python System Information

Overview

PSI is a Python module providing direct access to real-time system and process information. It is made up of several sub-modules.

The arch module gives some information about the system such as the system name and version, the machine architecture etc. It has a class representing each system and a factory function that will return an instance of the class which psi is running on currently.

The process module provides an interface to information about processes currently running on the system. Each process is represented as an instance of the Process class and additionally there is a ProcessTable class which is a dictionary of all running processes. To know exactly what attributes are available and what they mean you should look at the docstrings and examples below but important to note is that all the information is collected at instantiation time. So the contents of ProcessTable and Process instances are really snapshots and will still contain all information even after the actual process has gone.

Lastly there are some general functions available directly under the psi namespace such as loadavg(), getzoneid() etc. Once more see the docstrings for detailed information.

Some information may not be available on all platforms, rather then trying to emulate this information these parts of the API just don't exists on those platforms. Examples of these are: psi.process.Process.pcpu which is not available on Linux, psi.getzoneid() which is only available on SunOS 10 and above etc. If not all information can be found some attribute descriptors of objects might return subclasses of AttributeError, allowing you to use generic getattr() semantics as well as more specifically detect why an attribute is not available (insufficient privileges, not implemented, ...).

Install

You need to check if it's supported on your platform, check the docstring of setup.py for the exact supported platforms.

You will also need a working C compiler and the python development files. If a system is not supported yet the build will fail. After building it is best to run the test suite, on some platforms not all tests will pass yet and you would rather know of these problems before starting to use PSI.

So to fully install PSI from source:

$ python setup.py build
$ python setup.py test [--all]
$ python setup.py install [<your options>]

See the Python documentation on installing Python module for more control: http://docs.python.org/install/index.html

Here a rough list of packages you will need for some popular GNU/Linux distributions, this should give you an idea of what is needed.

Debian/Ubuntu:

  • python
  • python-dev
  • gcc

Redhat/CentOS:

  • python
  • python-devel
  • gcc

Limitations

Solaris

If the module is compiled as 32-bit (which is what will usually happen since that tends to be how python is compiled) it will use the ILP32 model and will not be able to read the address space of 64-bit processes as they use the LP64 model. This means that the full argument list and the environment dictionary will not be available. The partial argument list can still be retrieved from the psi.process.Process.command attribute.

Unit Tests

To run the unit tests:

$ python setup.py test [--all]

The --all option will run tests that require superuser privileges, this is required to run some test applications under specific schedulers and priorities to test if psi does detect these correctly. To acquire superuser privileges sudo is used when available, falling back to "su -c".

If any tests fail, please copy & paste the output and send operating system version, python version, python executable format (32/64-bit) and any other applicable details to the mailing list (psi-discuss@googlegroups.com).

Examples

Examples are the best documentation. :-)

Python 2.5.2 (r252:60911, Oct  5 2008, 19:24:49)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import psi
>>>
>>> a = psi.arch.arch_type()
>>> a
psi.arch.ArchLinux()
>>> isinstance(a, psi.arch.ArchLinux)
True
>>> isinstance(a, psi.arch.ArchSunOS)
False
>>> a.sysname
'Linux'
>>> a.nodename
'signy'
>>> a.release
'2.6.27-9-generic'
>>> a.release_info
(2L, 6L, 26L)
>>> a.version
'#1 SMP Thu Nov 20 21:57:00 UTC 2008'
>>> a.machine
'i686'
>>>
>>> psi.loadavg()
(0.059999999999999998, 0.13, 0.13)
>>>
>>> import os
>>> mypid = os.getpid()
>>> mypid
21374
>>> p = psi.process.Process(mypid)
>>> p.args
('python',)
>>> p.exe
'/usr/bin/python2.5'
>>> p.uid
1000
>>> import pwd
>>> pwd.getpwuid(p.uid)
pwd.struct_passwd(pw_name='flub', pw_passwd='x', pw_uid=1000,
pw_gid=1000, pw_gecos='Floris Bruynooghe,,,', pw_dir='/home/flub',
pw_shell='/bin/bash')
>>> p.start_time
datetime.datetime(2009, 5, 11, 20, 4, 31, 709993)
>>> help(psi.process.Process.start_time)
Help on getset descriptor psi.process.Process.start_time:

start_time
  Start time of process as datetime.datetime object

  Use .strftime('%s') to get seconds since epoch
>>> p.ppid
21304L
>>> parent = psi.process.Process(pid=p.ppid)
>>> parent.args
('bash',)
>>> p.rss
2293L
>>>
>>> pt = psi.process.ProcessTable()
>>> len(pt)
145
>>> pt.keys()
[1L, 2L, 3L, 4L, 5L, 6L, 7L, 6152L, 5660L, 6687L, 4648L, 5674L,
5639L, 6834L, 46L, 48L, 50L, 51L, 5684L, 1081L, 2621L, 5184L, 6276L,
2627L, 6217L, 6220L, 6221L, 4877L, 6224L, 6227L, 6229L, 6235L,
6757L, 5729L, 6244L, 2149L, 6246L, 2152L, 2153L, 6763L, 6764L,
6254L, 6248L, 6259L, 5749L, 2166L, 6249L, 2169L, 5242L, 2683L,
6781L, 6273L, 6274L, 4740L, 6278L, 6279L, 5772L, 5776L, 6290L,
5779L, 5268L, 6296L, 6809L, 156L, 157L, 158L, 6341L, 6307L, 2212L,
6257L, 20654L, 6856L, 4786L, 4788L, 5814L, 5817L, 6263L, 5821L,
6261L, 6336L, 4811L, 118L, 200L, 1739L, 5837L, 1742L, 1743L, 6349L,
20693L, 6265L, 5852L, 122L, 4833L, 4834L, 1253L, 2793L, 1258L,
6382L, 21374L, 6393L, 5885L, 1278L, 5376L, 6401L, 5675L, 1290L,
1293L, 6445L, 5397L, 6262L, 5913L, 4385L, 4386L, 4392L, 4393L,
4394L, 1074L, 6449L, 5426L, 6456L, 6458L, 5951L, 19779L, 5963L,
5964L, 21327L, 21304L, 5466L, 4955L, 4444L, 2404L, 5501L, 6526L,
4992L, 4993L, 6032L, 6572L, 6442L, 5573L, 5576L, 2794L, 17357L,
4054L, 6397L, 6136L]
>>> q = pt[6856]
>>> q.args
('emacs22-gtk',)
>>> q.env
{'GNOME_DESKTOP_SESSION_ID': 'this-is-deprecated', 'LOGNAME':
'flub', 'USER': 'flub', 'HOME': '/home/flub', 'PATH':
'/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games',
'DISPLAY': ':0.0', 'SSH_AGENT_PID': '6217', 'LANG': 'en_GB.UTF-8',
'SHELL': '/bin/bash', 'XDG_SESSION_COOKIE':
'26100f517aa94dec0dc7b4aa494948ea-1231927234.615881-1120709651',
'SESSION_MANAGER': 'local/signy:/tmp/.ICE-unix/6152',
'XDG_DATA_DIRS': '/usr/local/share/:/usr/share/:/usr/share/gdm/',
'WINDOWPATH': '7', 'GPG_AGENT_INFO':
'/tmp/seahorse-SWS6qW/S.gpg-agent:6235:1', 'USERNAME': 'flub',
'GDM_XSERVER_LOCATION': 'local', 'SSH_AUTH_SOCK':
'/tmp/keyring-AStyaD/ssh', 'DESKTOP_SESSION': 'gnome', 'GDMSESSION':
'gnome', 'DBUS_SESSION_BUS_ADDRESS':
'unix:abstract=/tmp/dbus-HFM6sYANYS,guid=916b5b81c03bda327eaaa293496db7c5',
'ORBIT_SOCKETDIR': '/tmp/orbit-flub', 'XAUTHORITY':
'/home/flub/.Xauthority', 'GNOME_KEYRING_SOCKET':
'/tmp/keyring-AStyaD/socket', 'GNOME_KEYRING_PID': '6246\n',
'GDM_LANG': 'en_GB.UTF-8', 'PWD': '/home/flub', 'GTK_RC_FILES':
'/etc/gtk/gtkrc:/home/flub/.gtkrc-1.2-gnome2'}
>>>
>>> r = []
>>> for pp in pt.values():
...     if pp.args and 'evolution' in pp.args[0]:
...         r.append(pp)
...
>>> r
[psi.process.Process(pid=6336), psi.process.Process(pid=6572),
psi.process.Process(pid=6397)]
>>> for pp in r:
...     print ' '.join(pp.args)
...
/usr/lib/evolution/2.24/evolution-exchange-storage --oaf-activate-iid=OAFIID:GNOME_Evolution_Exchange_Connector_CalFactory:1.2 --oaf-ior-fd=22
evolution
/usr/lib/evolution/evolution-data-server-2.24 --oaf-activate-iid=OAFIID:GNOME_Evolution_DataServer_CalFactory:1.2 --oaf-ior-fd=23
>>>
>>> init = psi.process.Process(1)
>>> init.env
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
psi.InsufficientPrivsError: Insufficient privileges for Process.env
>>>

Some sample scripts are also available in the examples/ subdirectory.

Development

You should definitely read the DESIGN file, it will explain the ideas behind how the code is structured and how you should extend it. Also very useful is the TODO file and the wiki (http://www.psychofx.com/psi/trac/wiki/Development).

The setup.py has some extra features that help with development, these are explained in its docstring.

The PSI source code is hosted at bitbucket in a Mercurial repository, http://bitbucket.org/chrismiles/psi/

Porting

If PSI does not yet work on your architecture/system then it needs to be ported, the design is aimed at making this easy for you. There is no separate porting guide at the moment so you will have to read the DESIGN file for details of what to do.

Help

There is a mailing list at psi-discuss@googlegroups.com where you can post questions, patches, hints, bugs, etc. Your feedback is welcome!