Sunday, May 15, 2016

psutil 4.2.0, Windows services and Python

New psutil 4.2.0 is out. The main feature of this release is the support for Windows services:

>>> import psutil
>>> list(psutil.win_service_iter())
[<WindowsService(name='AeLookupSvc', display_name='Application Experience') at 38850096>,
 <WindowsService(name='ALG', display_name='Application Layer Gateway Service') at 38850128>,
 <WindowsService(name='APNMCP', display_name='Ask Update Service') at 38850160>,
 <WindowsService(name='AppIDSvc', display_name='Application Identity') at 38850192>,
 ...]
>>> s = psutil.win_service_get('alg')
>>> s.as_dict()
{'binpath': 'C:\\Windows\\System32\\alg.exe',
 'description': 'Provides support for 3rd party protocol plug-ins for Internet Connection Sharing',
 'display_name': 'Application Layer Gateway Service',
 'name': 'alg',
 'pid': None,
 'start_type': 'manual',
 'status': 'stopped',
 'username': 'NT AUTHORITY\\LocalService'}

I did this mainly because I find pywin32 APIs too low level. Having something like this in psutil can be useful to discover and monitor services more easily. The code changes are here and here's the doc. The API for querying a service is similar to psutil.Process. You can get a reference to a service object by using its name (which is unique for every service) and then use name(), status(), etc..:

>>> s = psutil.win_service_get('alg')
>>> s.name()
'alg'
>>> s.status()
'stopped'

Initially I thought to expose and provide a complete set of APIs to handle all aspects of service handling including start(), stop(), restart(), install(), uninstall() and modify() but I soon realized that I would have ended up reimplementing what pywin32 already provides at the cost of overcrowding psutil API (see my reasoning here). I think psutil should really be about monitoring, not about installing and modifying system stuff, especially something as critical as a Windows service.

Considerations about Windows services

For those of you who are not familiar with Windows, a service is something, generally an executable (.exe), which runs at system startup and keeps running in background. We can say they are the equivalent of a UNIX init script. All service are controlled by a "manager" which keeps track of their status and metadata (e.g. description, startup type) and with that you can start and stop them. It is interesting to note that since (most) services are bound to an executable (and hence a process) you can reference the process via its PID:

>>> s = psutil.win_service_get('sshd')
>>> s
<WindowsService(name='sshd', display_name='Open SSH server') at 38853046>
>>> s.pid()
1865
>>> p = psutil.Process(1865)
>>> p
<psutil.Process(pid=19547, name='sshd.exe') at 140461487781328>
>>> p.exe()
'C:\CygWin\bin\sshd'

Other improvements

psutil 4.2.0 comes with 2 other enhancements for Linux:
  • psutil.virtual_memory() returns a new "shared" memory field. This is the same value reported by "free" cmdline utility.
  • I changed the way how /proc was parsed. Instead of reading /proc/{pid}/status line by line I used a regular expression. Here's the speedups:
    * Process.ppid() is 20% faster
    * Process.status() is 28% faster
    * Process.name() is 25% faster
    * Process.num_threads() is 20% faster (on Python 3 only; on Python 2 it's a bit slower - I
       suppose re module received some improvements)

Links

Wednesday, February 17, 2016

psutil 4.0.0 and how to get "real" process memory and environ in Python

New psutil 4.0.0 is out, with some interesting news about process memory metrics. I'll just get straight to the point and describe what's new.

"Real" process memory info

Determining how much memory a process really uses is not an easy matter (see this and this). RSS (Resident Set Size), which is what most people usually rely on, is misleading because it includes both the memory which is unique to the process and the memory shared with other processes. What would be more interesting in terms of profiling is the memory which would be freed if the process was terminated right now. In the Linux world this is called USS (Unique Set Size), and this is the major feature which was introduced in psutil 4.0.0 (not only for Linux but also for Windows and OSX).

USS memory

The USS (Unique Set Size) is the memory which is unique to a process and which would be freed if the process was terminated right now. On Linux this can be determined by parsing all the "private" blocks in /proc/pid/smaps. The Firefox team pushed this further and managed to do the same also on OSX and Windows, which is great. New version of psutil is now able to do the same:
>>> psutil.Process().memory_full_info()
pfullmem(rss=101990, vms=521888, shared=38804, text=28200, lib=0, data=59672, dirty=0, 
         uss=81623, pss=91788, swap=0)

PSS and swap

On Linux there are two additional metrics which can also be determined via /proc/pid/smaps: PSS and swap. PSS, aka "Proportional Set Size", represents the amount of memory shared with other processes, accounted in a way that the amount is divided evenly between the processes that share it. I.e. if a process has 10 MBs all to itself (USS) and 10 MBs shared with another process, its PSS will be 15 MBs. "swap" is simply the amount of memory that has been swapped out to disk. With memory_full_info() it is possible to implement a tool like this, similar to smem on Linux, which provides a list of processes sorted by "USS". It is interesting to notice how RSS differs from USS:
~/svn/psutil$ ./scripts/procsmem.py
PID     User    Cmdline                            USS     PSS    Swap     RSS
==============================================================================
...
3986    giampao /usr/bin/python3 /usr/bin/indi   15.3M   16.6M      0B   25.6M
3906    giampao /usr/lib/ibus/ibus-ui-gtk3       17.6M   18.1M      0B   26.7M
3991    giampao python /usr/bin/hp-systray -x    19.0M   23.3M      0B   40.7M
3830    giampao /usr/bin/ibus-daemon --daemoni   19.0M   19.0M      0B   21.4M
20529   giampao /opt/sublime_text/plugin_host    19.9M   20.1M      0B   22.0M
3990    giampao nautilus -n                      20.6M   29.9M      0B   50.2M
3898    giampao /usr/lib/unity/unity-panel-ser   27.1M   27.9M      0B   37.7M
4176    giampao /usr/lib/evolution/evolution-c   35.7M   36.2M      0B   41.5M
20712   giampao /usr/bin/python -B /home/giamp   45.6M   45.9M      0B   49.4M
3880    giampao /usr/lib/x86_64-linux-gnu/hud/   51.6M   52.7M      0B   61.3M
20513   giampao /opt/sublime_text/sublime_text   65.8M   73.0M      0B   87.9M
3976    giampao compiz                          115.0M  117.0M      0B  130.9M
32486   giampao skype                           145.1M  147.5M      0B  149.6M

Implementation

In order to get these values (USS, PSS and swap) we need to pass through the whole process address space. This usually requires higher user privileges and is considerably slower than getting the "usual" memory metrics via Process.memory_info(), which is probably the reason why tools like ps and top show RSS/VMS instead of USS. A big thanks goes to the Mozilla team which figured out all this stuff on Windows and OSX, and to Eric Rahm who put the PRs for psutil together (see #744, #745 and #746). For those of you who don't use Python and would like to port the code on other languages here's the interesting parts:

Memory type percent

After reorganizing process memory APIs I decided to add a new memtype parameter to Process.memory_percent(). With this it is now possible to compare a specific memory type (not only RSS) against the total physical memory. E.g.
>>> psutil.Process().memory_percent(memtype='pss')
0.06877466326787016

Process environ

Second biggest improvement in psutil 4.0.0 is the ability to determine the process environment variables. This opens interesting possibilities about process recognition and monitoring techniques. For instance, one might start a process by passing a certain custom environment variable, then iterate over all processes to find the one of interest (and figure out whether it's running or whatever):
import psutil
for p in psutil.process_iter():
    try:
        env = p.environ()
    except psutil.Error:
        pass
    else:
        if 'MYAPP' in env:
            ...
Process environ was a long standing issue (year 2009) who I gave up to implement because the Windows implementation worked for the current process only. Frank Benkstein solved that and the process environ can now be determined on Linux, Windows and OSX for all processes (of course you may still bump into AccessDenied for processes owned by another user):
>>> import psutil
>>> from pprint import pprint as pp
>>> pp(psutil.Process().environ())
{...
 'CLUTTER_IM_MODULE': 'xim',
 'COLORTERM': 'gnome-terminal',
 'COMPIZ_BIN_PATH': '/usr/bin/',
 'HOME': '/home/giampaolo',
 'PWD': '/home/giampaolo/svn/psutil',
  }
>>>
It must be noted that the resulting dict usually does not reflect changes made after the process started (e.g. os.environ['MYAPP'] = '1'). Again, for whoever is interested in doing this in other languages, here's the interesting parts:

Extended disk IO stats

psutil.disk_io_counters() has been extended to report additional metrics on Linux and FreeBSD:
  • busy_time, which is the time spent doing actual I/Os (in milliseconds).
  • read_merged_count and write_merged_count (Linux only), which is number of merged reads and writes (see iostats doc)
With these new metrics it is possible to have a better representation of actual disk utilization, similarly to iostat command on Linux.

OS constants

Given the increasing number of platform-specific metrics I added a new set of constants to quickly differentiate what platform you're on: psutil.LINUX, psutil.WINDOWS, etc.

Main bug fixes


  • #734: on Python 3 invalid UTF-8 data was not correctly handled for proces name(), cwd(), exe(), cmdline() and open_files() methods, resulting in UnicodeDecodeError. This was affecting all platforms. Now surrogateescape error handler is used as a workaround for replacing the corrupted data.
  • #761: [Windows] psutil.boot_time() no longer wraps to 0 after 49 days.
  • #767: [Linux] disk_io_counters() may raise ValueError on 2.6 kernels and it's  broken on 2.4 kernels.
  • #764: psutil can now be compiled on NetBSD-6.X.
  • #704: psutil can now be compiled on Solaris sparc.
Complete list of bug fixes is available here.

Porting code

Being 4.0.0 a major version, I took the chance to (lightly) change / break some APIs.
  • Process.memory_info() no longer returns just an (rss, vms) namedtuple. Instead it returns a namedtuple of variable length, changing depending on the platform (rss and vms are always present though, also on Windows). Basically it returns the same result of old process_memory_info_ex(). This shouldn't break your existent code, unless you were doing "rss, vms = p.memory_info()".
  • At the same time process_memory_info_ex() is now deprecated. The method is still there as an alias for memory_info(), issuing a deprecation warning.
  • psutil.disk_io_counters() returns 2 additional fields on Linux and 1 additional field on FreeBSD. 
  • psutil.disk_io_counters() on NetBSD and OpenBSD no longer return write_count and read_count metrics because the kernel do not provide them (we were returning the busy time instead). I also don't expect this to be a big issue because NetBSD and OpenBSD support is very recent.

Final notes and looking for a job

OK, this is it. I would like to spend a couple more words to announce the world that I'm currently unemployed and looking for a remote gig again! =) I want remote because my plan for this year is to remain in Prague (Czech Republic) and possibly spend 2-3 months in Asia. If you know about any company who's looking for a Python backend dev who can work from afar feel free to share my Linkedin profile or mail me at g.rodola [at] gmail [dot] com.

External links

Friday, February 12, 2016

How to always execute exit functions in Python

...or why atexit.register() and signal.signal() are evil

UPDATE (2016-02-13): this recipe no longer handles SIGINT, SIGQUIT and SIGABRT as aliases for "application exit" because it was a bad idea. It only handles SIGTERM. Also it no longer support Windows because signal.signal() implementation is too different than POSIX.

Many people erroneously think that any function registered via atexit module is guaranteed to always be executed when the program terminates. You may have noticed this is not the case when, for example, you daemonize your app in production then try to stop it or restart it: the cleanup functions will not be executed. This is because functions registered wth atexit module are not called when the program is killed by a signal:
import atexit, os, signal

@atexit.register
def cleanup():
    print("on exit")  # XXX this never gets printed

os.kill(os.getpid(), signal.SIGTERM)

It must be noted that the same thing would happen if instead of atexit.register() we would use a "finally" clause. It turns out the correct way to make sure the exit function is always called in case a signal is received is to register it via signal.signal(). That has a drawback though: in case a third-party module has already registered a function for that signal (SIGTERM or whatever), your new function will overwrite the old one:

import os, signal

def old(*args):
    print("old")  # XXX this never gets printed

def new(*args):
    print("new")

signal.signal(signal.SIGTERM, old)
signal.signal(signal.SIGTERM, new)
os.kill(os.getpid(), signal.SIGTERM)

Also, we would still have to use atexit.register() so that the function is called also on "clean" interpreter exit and take into account other signals other than SIGTERM which would cause the process to terminate. This recipe attempts to address all these issues so that:
  •  the exit function is always executed for all exit signals (SIGTERM, SIGINT, SIGQUIT, SIGABRT) on SIGTERM and on "clean" interpreter exit.
  • any exit function(s) previously registered via atexit.register() or signal.signal() will be executed as well (after the new one). 
  • It must be noted that the exit function will never be executed in case of SIGKILL, SIGSTOP or os._exit().

The code

"""
Function / decorator which tries very hard to register a function to
be executed at importerer exit.

Author: Giampaolo Rodola'
License: MIT
"""

from __future__ import print_function
import atexit
import os
import functools
import signal
import sys


_registered_exit_funs = set()
_executed_exit_funs = set()


def register_exit_fun(fun=None, signals=[signal.SIGTERM],
                      logfun=lambda s: print(s, file=sys.stderr)):
    """Register a function which will be executed on "normal"
    interpreter exit or in case one of the `signals` is received
    by this process (differently from atexit.register()).
    Also, it makes sure to execute any other function which was
    previously registered via signal.signal(). If any, it will be
    executed after our own `fun`.

    Functions which were already registered or executed via this
    function will be ignored.

    Note: there's no way to escape SIGKILL, SIGSTOP or os._exit(0)
    so don't bother trying.

    You can use this either as a function or as a decorator:

        @register_exit_fun
        def cleanup():
            pass

        # ...or

        register_exit_fun(cleanup)

    Note about Windows: I tested this some time ago and didn't work
    exactly the same as on UNIX, then I didn't care about it
    anymore and didn't test since then so may not work on Windows.

    Parameters:

    - fun: a callable
    - signals: a list of signals for which this function will be
      executed (default SIGTERM)
    - logfun: a logging function which is called when a signal is
      received. Default: print to standard error. May be set to
      None if no logging is desired.
    """
    def stringify_sig(signum):
        if sys.version_info < (3, 5):
            smap = dict([(getattr(signal, x), x) for x in dir(signal)
                         if x.startswith('SIG')])
            return smap.get(signum, signum)
        else:
            return signum

    def fun_wrapper():
        if fun not in _executed_exit_funs:
            try:
                fun()
            finally:
                _executed_exit_funs.add(fun)

    def signal_wrapper(signum=None, frame=None):
        if signum is not None:
            if logfun is not None:
                logfun("signal {} received by process with PID {}".format(
                    stringify_sig(signum), os.getpid()))
        fun_wrapper()
        # Only return the original signal this process was hit with
        # in case fun returns with no errors, otherwise process will
        # return with sig 1.
        if signum is not None:
            if signum == signal.SIGINT:
                raise KeyboardInterrupt
            # XXX - should we do the same for SIGTERM / SystemExit?
            sys.exit(signum)

    def register_fun(fun, signals):
        if not callable(fun):
            raise TypeError("{!r} is not callable".format(fun))
        set([fun])  # raise exc if obj is not hash-able

        signals = set(signals)
        for sig in signals:
            # Register function for this signal and pop() the previously
            # registered one (if any). This can either be a callable,
            # SIG_IGN (ignore signal) or SIG_DFL (perform default action
            # for signal).
            old_handler = signal.signal(sig, signal_wrapper)
            if old_handler not in (signal.SIG_DFL, signal.SIG_IGN):
                # ...just for extra safety.
                if not callable(old_handler):
                    continue
                # This is needed otherwise we'll get a KeyboardInterrupt
                # strace on interpreter exit, even if the process exited
                # with sig 0.
                if (sig == signal.SIGINT and
                        old_handler is signal.default_int_handler):
                    continue
                # There was a function which was already registered for this
                # signal. Register it again so it will get executed (after our
                # new fun).
                if old_handler not in _registered_exit_funs:
                    atexit.register(old_handler)
                    _registered_exit_funs.add(old_handler)

        # This further registration will be executed in case of clean
        # interpreter exit (no signals received).
        if fun not in _registered_exit_funs or not signals:
            atexit.register(fun_wrapper)
            _registered_exit_funs.add(fun)

    # This piece of machinery handles 3 usage cases. register_exit_fun()
    # used as:
    # - a function
    # - a decorator without parentheses
    # - a decorator with parentheses
    if fun is None:
        @functools.wraps
        def outer(fun):
            return register_fun(fun, signals)
        return outer
    else:
        register_fun(fun, signals)
        return fun

Usage

As a function:
def cleanup():
    print("cleanup")

register_exit_fun(cleanup)
As a decorator:
@register_exit_fun
def cleanup():
    print("cleanup")

Unit tests

This recipe is hosted on ActiveState and has a full set of unittests. It works with Python 2 and 3.

Notes about Windows

On Windows signals are only partially supported meaning a function which was previously registered via signal.signal() will be executed only on interpreter exit, but not if the process receives a signal. Apparently this is a limitation either of Windows or the signal module (most likely Windows).

Because of how different signal.signal() behaves on Windows, this code is UNIX only: http://bugs.python.org/issue26350

Proposal for stdlib inclusion

The fact that atexit module does not handle signals and that signal.signal() overwrites previously registered handlers is unfortunate. It is also confusing because it is not immediately clear which one you are supposed to use (and it turns out you're supposed to use both). Most of the times you have no idea (or don't care) that you're overwriting another exit function. As a user, I would just want to execute an exit function, no matter what, possibly without messing with whatever a module I've previously imported has done with signal.signal(). To me this suggests there could be space for something like "atexit.register_w_signals".

External discussions

Friday, January 15, 2016

NetBSD support for psutil

Roughly two months have passed since I last announced psutil added support for OpenBSD platforms. Today I am happy to announce we also have NetBSD support! This was contributed by Thomas KlausnerRyo Onodera and myself in PR #570.

Differences with FreeBSD (and OpenBSD)

NetBSD implementation has similar limitations as the ones I encountered with OpenBSD. Again, FreeBSD presents itself as the BSD variant with the best support in terms of kernel functionalities.
As for the rest: it is all there. All memory, disk, network and process APIs are fully supported and functioning.

Other enhancements available in this psutil release

Other than NetBSD support this new release has a couple of interesting enhancements:

  • #708: [Linux] psutil.net_connections() and Process.connections() on Python can be up to 3x faster in case of many connections.
  • #718: process_iter() is now thread safe.
You can read the rest in the HISTORY file, as usual.

Move to Prague

As a personal note I'd like to add that I'm currently in Prague (Czech Republic) and I'm thinking about moving down here for a while. The city is great and girls are beautiful. ;-)

External discussions

Tuesday, November 24, 2015

OpenBSD support for psutil

OK, this is a big one: starting from version 3.3.0 (released just now) psutil will officially support OpenBSD platforms. This was contributed by Landry Breuil (thanks dude!) and myself in PR #615. The interesting parts of the code changes are this and this.

Differences with FreeBSD

As expected, OpenBSD implementation is very similar to FreeBSD's (which was already in place), that is why I decided to merge most of it in a single C file (_psutil_bsd.c) and use 2 separate C files for when the two implementations differed too much: freebsd.c and openbsd.c. In terms of functionality here's the differences with FreeBSD. Unless specified, these differences are due to the kernel which does not provide the information natively (meaning we can't do anything about it).
Similarly to FreeBSD, also OpenBSD implementation of Process.open_files() is problematic as it is not able to return file paths (FreeBSD can sometimes). Other than these differences the functionalities are all there and pretty much the same, so overall I'm pretty satisfied with the result. 

Considerations about BSD platforms

psutil has been supporting FreeBSD basically since the beginning (year 2009). At the time it made sense to support FreeBSD instead of other BSD variants because it is the most popular, followed by OpenBSD and NetBSD. Compared to FreeBSD, OpenBSD appears to be more "minimal" both in terms of facilities provided by the kernel and the number of system administration tools available. One thing which I appreciate a lot about FreeBSD is that the source code of all CLI tools installed on the system is available under /usr/bin/src, which was a big help for implementing all psutil APIs. OpenBSD source code is also available but it uses CSV and I am not sure it includes the source code for all CLI tools. There are still two more BSD variants for which it may be worth to add support for: NetBSD and DragonflyBSD (in this order). About a year ago some guy provided a patch for adding basic NetBSD support so it is likely that will happen sooner or later.

Other enhancements available in this release

The only other enhancement is issue #558, which allows specifying a different location of /proc filesystem on Linux.

External discussions


Saturday, June 13, 2015

psutil 3.0

Here we are. It's been a long time since my last blog post and my last psutil release. The reason? I've been travelling! I mean... a lot. I've spent 3 months in Berlin, 3 weeks in Japan and 2 months in New York City. While I was there I finally had the chance to meet my friend Jay Loden in person. Jay and I originally started working on psutil together 7 years ago



Back then I didn't know any C (and I still am a terrible C developer) so he's been crucial to develop the initial psutil skeleton including OSX and Windows support. I'm back home now (but not for long ;-)), so I finally have some time to write this blog post and tell you about the new psutil release. Let's see what happened.

net_if_addrs()

In a few words, we're now able to list network interface addresses similarly to "ifconfig" command on UNIX:
>>> import psutil
>>> psutil.net_if_addrs()
{'eth0': [snic(
            family=<AddressFamily.AF_INET: 2>, 
            address='10.0.0.4', 
            netmask='255.0.0.0', 
            broadcast='10.255.255.255'),
          snic(
            family=<AddressFamily.AF_PACKET: 17>, 
            address='9c:eb:e8:0b:05:1f', 
            netmask=None, 
            broadcast='ff:ff:ff:ff:ff:ff')],
 'lo': [snic(
            family=<AddressFamily.AF_INET: 2>, 
            address='127.0.0.1', 
            netmask='255.0.0.0', 
            broadcast='127.0.0.1'),
        snic(
            family=<AddressFamily.AF_PACKET: 17>, 
            address='00:00:00:00:00:00', 
            netmask=None, 
            broadcast='00:00:00:00:00:00')]}
This is limited to AF_INET (IPv4), AF_INET6 (IPv6) and AF_LINK (ETHERNET) address families. If you want something more poweful (e.g. AF_BLUETOOTH) you can take a look at netifaces extension. And here's the code which does these tricks on POSIX and Windows:
Also, here's some doc.

net_if_stats()

This will return a bunch of information about network interface cards:
>>> import psutil
>>> psutil.net_if_stats()
{'eth0': snicstats(
    isup=True, 
    duplex=<NicDuplex.NIC_DUPLEX_FULL: 2>, 
    speed=100, 
    mtu=1500),
 'lo': snicstats(
    isup=True, 
    duplex=<NicDuplex.NIC_DUPLEX_UNKNOWN: 0>, 
    speed=0, 
    mtu=65536)}
Again, here's the code:
...and the doc.

Enums

Enums are a nice new feature introduced in Python 3.4. Very briefly (or at least, this is what I appreciate the most about them), they help you write an API with human-readable constants. If you use Python 2 you'll see something like this:
>>> import psutil
>>> psutil.IOPRIO_CLASS_IDLE
3
On Python 3.4 you'll see a more informative:
>>> import psutil
>>> psutil.IOPRIO_CLASS_IDLE
<IOPriority.IOPRIO_CLASS_IDLE: 3>
They are backward compatible, meaning if you're sending serialized data produced with psutil through the network you can safely use comparison operators and so on. The psutil APIs returning enums (on Python >=3.4) are:
All the other existing constants remained plain strings (STATUS_*) or integers (CONN_*).

Zombie processes

This is a big one. The full story is here but basically the support for zombie processes on UNIX was broken (except on Linux - Windows doesn't have zombie processes). Up until psutil 2.* we could instantiate a zombie process:
>>> pid = create_zombie()
>>> p = psutil.Process(pid)
...but every time we queried it we got a NoSuchProcess exception:
>>> psutil.name()
  File "psutil/__init__.py", line 374, in _init
    raise NoSuchProcess(pid, None, msg)
psutil.NoSuchProcess: no process found with pid 123
That was misleading though because the PID technically still existed:
>>> psutil.pid_exists(p.pid)
True
Furthermore, depending on what platform you were on, certain process stats could still be queried (instead of raising NoSuchProcess):
>>> psutil.cmdline()
['python']
Also process_iter() did not return zombie processes at all. This was probably the worst aspect because being able to identify them is an important use case, as they signal an issue with process: if a parent process spawns a child, terminates it (via kill()), but doesn't wait() for it it will create a zombie. Long story short, the way this changed in psutil 3.0 is that:
  • we now have a new ZombieProcess exception, raised every time we're not able to query a process because it's a zombie
  • it is raised instead of NoSuchProcess (which was incorrect and misleading)
  • it is still backward compatible (meaning you won't have to change your old code) because it inherits from NoSuchProcess
  • process_iter() finally works, meaning you can safely identify zombie processes like this:
import psutil
zombies = []
for p in psutil.process_iter():
    try:
        if p.status() == psutil.STATUS_ZOMBIE:  
            zombies.append(p)
    except NoSuchProcess:
        pass

Removal of deprecated APIs

This is another big one, probably the biggest. In a previous blog post I already talked about deprecated APIs. What I did back then (January 2014) was to rename and officially deprecate different APIs and provide aliases for them so that people wouldn't yell at me because I broke their existent code. The most interesting deprecation was certainly the one affecting module constants and the hack which was used in order to provide "module properties". With this new release I decided to get rid of all those aliases. I'm sure this will cause problems but hey! This is a new major release, right? =). Plus the amount of crap which was removed is impressive (see the commit). Here's the old aliases which are now gone for good (or bad, depending on how much headache they will cause you):

Removed module functions and constants

Already deprecated nameNew name
psutil.BOOT_TIME()psutil.boot_time()
psutil.NUM_CPUS()psutil.cpu_count()
psutil.TOTAL_PHYMEM()psutil.virtual_memory().total
psutil.avail_phymem()psutil.virtual_memory().free
psutil.avail_virtmem()psutil.swap_memory().free
psutil.cached_phymem() (Linux only)psutil.virtual_memory().cached
psutil.get_pid_list()psutil.pids().cached
psutil.get_process_list()-
psutil.get_users()psutil.users()
psutil.network_io_counters()psutil.net_io_counters()
psutil.phymem_buffers() (Linux only)psutil.virtual_memory().buffers
psutil.phymem_usage()psutil.virtual_memory()
psutil.total_virtmem()psutil.swap_memory().total
psutil.used_virtmem()psutil.swap_memory().used
psutil.used_phymem()psutil.virtual_memory().used
psutil.virtmem_usage()psutil.swap_memory()

Process methods (assuming p = psutil.Process()):

Already deprecated nameNew name
p.get_children()p.children()
p.get_connections()p.connections()
p.get_cpu_affinity()p.cpu_affinity()
p.get_cpu_percent()p.cpu_percent()
p.get_cpu_times()p.cpu_times()
p.get_io_counters()p.io_counters()
p.get_ionice()p.ionice()
p.get_memory_info()p.memory_info()
p.get_ext_memory_info()p.memory_info_ex()
p.get_memory_maps()p.memory_maps()
p.get_memory_percent()p.memory_percent()
p.get_nice()p.nice()
p.get_num_ctx_switches()p.num_ctx_switches()
p.get_num_fds()p.num_fds()
p.get_num_threads()p.num_threads()
p.get_open_files()p.open_files()
p.get_rlimit()p.rlimit()
p.get_threads()p.threads()
p.getcwd()p.cwd()
p.set_cpu_affinity()p.cpu_affinity()
p.set_ionice()p.ionice()
p.set_nice()p.nice()
p.set_rlimit()p.rlimit()

If your code suddenly breaks with AttributeError after you upgraded psutil it means you were using one of those deprecated aliases. In that case just take a look at the table above and rename stuff in accordance.

Bug fixes

I fixed a lot of stuff (full list here), but here's the list of things which I think are worth mentioning:

Ease of development

These are not enhancements you will directly benefit from but I put some effort into making my life easier every time I work on psutil.
  • I care about psutil code being fully PEP8 compliant so I added a pre-commit GIT hook which runs flake8 on every commit and rejects it if the coding style is not compliant. The way I install this is via make install-git-hooks.
  • I added a make install-dev-deps command which installs all deps and stuff which is useful for testing (ipdb, coverage, etc).
  • A new make coverage command which runs coverage. With this I discovered some of parts in the code which weren't covered by tests and I fixed that.
  • I started using tox to easily test psutil against all supported Python versions (from 2.6 to 3.4) in one shot.
  • I reorganized tests so that now they can be easily executed with py.test and nose (before, only unittest runner was fully supported)

Final words

I must say I'm pretty satisfied with how psutil is going and the satisfaction I still get every time I work on it. Right now it gets almost 800.000 download a month, which is pretty great for a Python library. As of right now I consider psutil almost "completed" in terms of features, meaning I'm basically running out of ideas on what I should add next (see TODO). From now on the future development will probably focus on adding support for more exotic platforms (OpenBSD, NetBSD, Android). There also have been some discussions on python-ideas mailing list about including psutil into Python stdlib but, assuming that will ever happen, it's still far away in the future as it would require a lot of time which I currently don't have. That should be all. I hope you will all enjoy this new release.

Sunday, September 21, 2014

psutil 2.1.2: python wheels

psutil 2.1.2 is out. This release has been cooking for a while now, and that's because I've been travelling for the past 3 months between Spain, Japan and Germany. Hopefully I will be staying in Berlin for a while now, so I will have more time to dedicate to the project. The main new "feature" of this release is that other than the exe files, Windows users can now also benefit of Python wheels (full story is here) which are available on PYPI! Frankly I don't know much about the new wheels packaging system but long story short is that Windows users can now install psutil via pip and therefore also include it as a dependency into requirements.txt. Other than this 2.1.2 can basically be considered a bug-fix release, including some important fixes amongst which:
  • #506: restored Python 2.4 compatibility
  • #340: Process.get_open_files() no longer hangs on Windows (this was a very old and high-priority issue)
  • #501: disk_io_counters() may return negative values on Windows
  • #504: (Linux) couldn't build RPM packages via setup.py
The list of all fixes can be found here. For the next release I plan to drop support for Python 2.4 and 2.5 and hopefully network interfaces information similarly to ifconfig.