Stem Docs

Proc Utilities

Proc Utilities

Helper functions for querying process and system information from the /proc contents. Fetching information this way provides huge performance benefits over lookups via system utilities (ps, netstat, etc). For instance, resolving connections this way cuts the runtime by around 90% verses the alternatives. These functions may not work on all platforms (only Linux?).

The method for reading these files (and a little code) are borrowed from psutil, which was written by Jay Loden, Dave Daeschler, Giampaolo Rodola’ and is under the BSD license.

These functions are not being vended to stem users. They may change in the future, use them at your own risk.

Changed in version 1.3.0: Dropped the get_* prefix from several function names. The old names still work, but are deprecated aliases.

Module Overview:

is_available - checks if proc utilities can be used on this system
system_start_time - unix timestamp for when the system started
physical_memory - memory available on this system
cwd - provides the current working directory for a process
uid - provides the user id a process is running under
memory_usage - provides the memory usage of a process
stats - queries statistics about a process
file_descriptors_used - number of file descriptors used by a process
connections - provides the connections made by a process
stem.util.proc.Stat(enum)

Types of data available via the stats() function.

Stat

Description

COMMAND

command name under which the process is running

CPU_UTIME

total user time spent on the process

CPU_STIME

total system time spent on the process

START_TIME

when this process began, in unix time

stem.util.proc.is_available[source]

Checks if proc information is available on this platform.

Returns

True if proc contents exist on this platform, False otherwise

stem.util.proc.system_start_time[source]

Provides the unix time (seconds since epoch) when the system started.

Returns

float for the unix time of when the system started

Raises

IOError if it can’t be determined

stem.util.proc.physical_memory[source]

Provides the total physical memory on the system in bytes.

Returns

int for the bytes of physical memory this system has

Raises

IOError if it can’t be determined

stem.util.proc.cwd(pid)[source]

Provides the current working directory for the given process.

Parameters

pid (int) – process id of the process to be queried

Returns

str with the path of the working directory for the process

Raises

IOError if it can’t be determined

stem.util.proc.uid(pid)[source]

Provides the user ID the given process is running under.

Parameters

pid (int) – process id of the process to be queried

Returns

int with the user id for the owner of the process

Raises

IOError if it can’t be determined

stem.util.proc.memory_usage(pid)[source]

Provides the memory usage in bytes for the given process.

Parameters

pid (int) – process id of the process to be queried

Returns

tuple of two ints with the memory usage of the process, of the form (resident_size, virtual_size)

Raises

IOError if it can’t be determined

stem.util.proc.stats(pid, *stat_types)[source]

Provides process specific information. See the Stat enum for valid options.

Parameters
  • pid (int) – process id of the process to be queried

  • stat_types (Stat) – information to be provided back

Returns

tuple with all of the requested statistics as strings

Raises

IOError if it can’t be determined

stem.util.proc.file_descriptors_used(pid)[source]

Provides the number of file descriptors currently being used by a process.

New in version 1.3.0.

Parameters

pid (int) – process id of the process to be queried

Returns

int of the number of file descriptors used

Raises

IOError if it can’t be determined

stem.util.proc.connections(pid=None, user=None)[source]

Queries connections from the proc contents. This matches netstat, lsof, and friends but is much faster. If no pid or user are provided this provides all present connections.

Parameters
  • pid (int) – pid to provide connections for

  • user (str) – username to look up connections for

Returns

list of Connection instances

Raises

IOError if it can’t be determined

stem.util.proc.get_system_start_time

Provides the unix time (seconds since epoch) when the system started.

Returns

float for the unix time of when the system started

Raises

IOError if it can’t be determined

stem.util.proc.get_physical_memory

Provides the total physical memory on the system in bytes.

Returns

int for the bytes of physical memory this system has

Raises

IOError if it can’t be determined

stem.util.proc.get_cwd(pid)

Provides the current working directory for the given process.

Parameters

pid (int) – process id of the process to be queried

Returns

str with the path of the working directory for the process

Raises

IOError if it can’t be determined

stem.util.proc.get_uid(pid)

Provides the user ID the given process is running under.

Parameters

pid (int) – process id of the process to be queried

Returns

int with the user id for the owner of the process

Raises

IOError if it can’t be determined

stem.util.proc.get_memory_usage(pid)

Provides the memory usage in bytes for the given process.

Parameters

pid (int) – process id of the process to be queried

Returns

tuple of two ints with the memory usage of the process, of the form (resident_size, virtual_size)

Raises

IOError if it can’t be determined

stem.util.proc.get_stats(pid, *stat_types)

Provides process specific information. See the Stat enum for valid options.

Parameters
  • pid (int) – process id of the process to be queried

  • stat_types (Stat) – information to be provided back

Returns

tuple with all of the requested statistics as strings

Raises

IOError if it can’t be determined

stem.util.proc.get_connections(pid=None, user=None)

Queries connections from the proc contents. This matches netstat, lsof, and friends but is much faster. If no pid or user are provided this provides all present connections.

Parameters
  • pid (int) – pid to provide connections for

  • user (str) – username to look up connections for

Returns

list of Connection instances

Raises

IOError if it can’t be determined