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(*args, **kwds)[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(*args, **kwds)

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(*args, **kwds)

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)

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)

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)

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)

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)

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)

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(*args, **kwds)[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.get_physical_memory(*args, **kwds)[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.get_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.get_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.get_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.get_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.get_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