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# -*- coding: utf-8 -*-
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"""Manage background (threaded) jobs conveniently from an interactive shell.
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This module provides a BackgroundJobManager class. This is the main class
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meant for public usage, it implements an object which can create and manage
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new background jobs.
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It also provides the actual job classes managed by these BackgroundJobManager
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objects, see their docstrings below.
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This system was inspired by discussions with B. Granger and the
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BackgroundCommand class described in the book Python Scripting for
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Computational Science, by H. P. Langtangen:
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http://folk.uio.no/hpl/scripting
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(although ultimately no code from this text was used, as IPython's system is a
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separate implementation).
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$Id: background_jobs.py 638 2005-07-18 03:01:41Z fperez $
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"""
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#*****************************************************************************
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# Copyright (C) 2005 Fernando Perez <fperez@colorado.edu>
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#*****************************************************************************
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from IPython import Release
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__author__ = '%s <%s>' % Release.authors['Fernando']
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__license__ = Release.license
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# Code begins
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import threading,sys
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from IPython.ultraTB import AutoFormattedTB
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from IPython.genutils import warn,error
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class BackgroundJobManager:
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"""Class to manage a pool of backgrounded threaded jobs.
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Below, we assume that 'jobs' is a BackgroundJobManager instance.
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Usage summary (see the method docstrings for details):
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jobs.new(...) -> start a new job
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jobs() or jobs.status() -> print status summary of all jobs
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jobs[N] -> returns job number N.
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foo = jobs[N].result -> assign to variable foo the result of job N
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jobs[N].traceback() -> print the traceback of dead job N
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jobs.remove(N) -> remove (finished) job N
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jobs.flush_finished() -> remove all finished jobs
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As a convenience feature, BackgroundJobManager instances provide the
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utility result and traceback methods which retrieve the corresponding
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information from the jobs list:
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jobs.result(N) <--> jobs[N].result
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jobs.traceback(N) <--> jobs[N].traceback()
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While this appears minor, it allows you to use tab completion
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interactively on the job manager instance.
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In interactive mode, IPython provides the magic fuction %bg for quick
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creation of backgrounded expression-based jobs. Type bg? for details."""
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def __init__(self):
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# Lists for job management
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self.jobs_run = []
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self.jobs_comp = []
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self.jobs_dead = []
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# A dict of all jobs, so users can easily access any of them
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self.jobs_all = {}
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# For reporting
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self._comp_report = []
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self._dead_report = []
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# Store status codes locally for fast lookups
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self._s_created = BackgroundJobBase.stat_created_c
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self._s_running = BackgroundJobBase.stat_running_c
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self._s_completed = BackgroundJobBase.stat_completed_c
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self._s_dead = BackgroundJobBase.stat_dead_c
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def new(self,func_or_exp,*args,**kwargs):
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"""Add a new background job and start it in a separate thread.
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There are two types of jobs which can be created:
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1. Jobs based on expressions which can be passed to an eval() call.
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The expression must be given as a string. For example:
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job_manager.new('myfunc(x,y,z=1)'[,glob[,loc]])
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The given expression is passed to eval(), along with the optional
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global/local dicts provided. If no dicts are given, they are
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extracted automatically from the caller's frame.
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A Python statement is NOT a valid eval() expression. Basically, you
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can only use as an eval() argument something which can go on the right
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of an '=' sign and be assigned to a variable.
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For example,"print 'hello'" is not valid, but '2+3' is.
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2. Jobs given a function object, optionally passing additional
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positional arguments:
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job_manager.new(myfunc,x,y)
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The function is called with the given arguments.
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If you need to pass keyword arguments to your function, you must
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supply them as a dict named kw:
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job_manager.new(myfunc,x,y,kw=dict(z=1))
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The reason for this assymmetry is that the new() method needs to
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maintain access to its own keywords, and this prevents name collisions
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between arguments to new() and arguments to your own functions.
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In both cases, the result is stored in the job.result field of the
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background job object.
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Notes and caveats:
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1. All threads running share the same standard output. Thus, if your
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background jobs generate output, it will come out on top of whatever
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you are currently writing. For this reason, background jobs are best
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used with silent functions which simply return their output.
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2. Threads also all work within the same global namespace, and this
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system does not lock interactive variables. So if you send job to the
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background which operates on a mutable object for a long time, and
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start modifying that same mutable object interactively (or in another
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backgrounded job), all sorts of bizarre behaviour will occur.
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3. If a background job is spending a lot of time inside a C extension
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module which does not release the Python Global Interpreter Lock
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(GIL), this will block the IPython prompt. This is simply because the
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Python interpreter can only switch between threads at Python
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bytecodes. While the execution is inside C code, the interpreter must
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simply wait unless the extension module releases the GIL.
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4. There is no way, due to limitations in the Python threads library,
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to kill a thread once it has started."""
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if callable(func_or_exp):
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kw = kwargs.get('kw',{})
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job = BackgroundJobFunc(func_or_exp,*args,**kw)
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elif isinstance(func_or_exp,basestring):
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if not args:
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frame = sys._getframe(1)
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glob, loc = frame.f_globals, frame.f_locals
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elif len(args)==1:
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glob = loc = args[0]
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elif len(args)==2:
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glob,loc = args
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else:
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raise ValueError,\
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'Expression jobs take at most 2 args (globals,locals)'
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job = BackgroundJobExpr(func_or_exp,glob,loc)
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else:
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raise
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jkeys = self.jobs_all.keys()
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if jkeys:
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job.num = max(jkeys)+1
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else:
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job.num = 0
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self.jobs_run.append(job)
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self.jobs_all[job.num] = job
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print 'Starting job # %s in a separate thread.' % job.num
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job.start()
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return job
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def __getitem__(self,key):
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return self.jobs_all[key]
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def __call__(self):
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"""An alias to self.status(),
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This allows you to simply call a job manager instance much like the
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Unix jobs shell command."""
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return self.status()
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def _update_status(self):
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"""Update the status of the job lists.
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This method moves finished jobs to one of two lists:
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- self.jobs_comp: jobs which completed successfully
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- self.jobs_dead: jobs which finished but died.
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It also copies those jobs to corresponding _report lists. These lists
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are used to report jobs completed/dead since the last update, and are
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then cleared by the reporting function after each call."""
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run,comp,dead = self._s_running,self._s_completed,self._s_dead
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jobs_run = self.jobs_run
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for num in range(len(jobs_run)):
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job = jobs_run[num]
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stat = job.stat_code
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if stat == run:
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continue
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elif stat == comp:
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self.jobs_comp.append(job)
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self._comp_report.append(job)
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jobs_run[num] = False
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elif stat == dead:
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self.jobs_dead.append(job)
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self._dead_report.append(job)
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jobs_run[num] = False
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self.jobs_run = filter(None,self.jobs_run)
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def _group_report(self,group,name):
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"""Report summary for a given job group.
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Return True if the group had any elements."""
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if group:
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print '%s jobs:' % name
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for job in group:
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print '%s : %s' % (job.num,job)
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print
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return True
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def _group_flush(self,group,name):
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"""Flush a given job group
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Return True if the group had any elements."""
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njobs = len(group)
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if njobs:
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plural = {1:''}.setdefault(njobs,'s')
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print 'Flushing %s %s job%s.' % (njobs,name,plural)
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group[:] = []
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return True
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def _status_new(self):
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"""Print the status of newly finished jobs.
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Return True if any new jobs are reported.
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This call resets its own state every time, so it only reports jobs
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which have finished since the last time it was called."""
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self._update_status()
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new_comp = self._group_report(self._comp_report,'Completed')
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new_dead = self._group_report(self._dead_report,
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'Dead, call job.traceback() for details')
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self._comp_report[:] = []
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self._dead_report[:] = []
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return new_comp or new_dead
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def status(self,verbose=0):
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"""Print a status of all jobs currently being managed."""
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self._update_status()
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self._group_report(self.jobs_run,'Running')
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self._group_report(self.jobs_comp,'Completed')
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self._group_report(self.jobs_dead,'Dead')
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# Also flush the report queues
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self._comp_report[:] = []
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self._dead_report[:] = []
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def remove(self,num):
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"""Remove a finished (completed or dead) job."""
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try:
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job = self.jobs_all[num]
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except KeyError:
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error('Job #%s not found' % num)
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else:
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stat_code = job.stat_code
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if stat_code == self._s_running:
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error('Job #%s is still running, it can not be removed.' % num)
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return
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elif stat_code == self._s_completed:
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self.jobs_comp.remove(job)
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elif stat_code == self._s_dead:
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self.jobs_dead.remove(job)
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def flush_finished(self):
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"""Flush all jobs finished (completed and dead) from lists.
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Running jobs are never flushed.
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It first calls _status_new(), to update info. If any jobs have
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completed since the last _status_new() call, the flush operation
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aborts."""
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if self._status_new():
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error('New jobs completed since last '\
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'_status_new(), aborting flush.')
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return
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# Remove the finished jobs from the master dict
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jobs_all = self.jobs_all
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for job in self.jobs_comp+self.jobs_dead:
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del(jobs_all[job.num])
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# Now flush these lists completely
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fl_comp = self._group_flush(self.jobs_comp,'Completed')
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fl_dead = self._group_flush(self.jobs_dead,'Dead')
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if not (fl_comp or fl_dead):
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print 'No jobs to flush.'
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def result(self,num):
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"""result(N) -> return the result of job N."""
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try:
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return self.jobs_all[num].result
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except KeyError:
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error('Job #%s not found' % num)
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def traceback(self,num):
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try:
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self.jobs_all[num].traceback()
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except KeyError:
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error('Job #%s not found' % num)
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class BackgroundJobBase(threading.Thread):
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"""Base class to build BackgroundJob classes.
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The derived classes must implement:
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- Their own __init__, since the one here raises NotImplementedError. The
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derived constructor must call self._init() at the end, to provide common
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initialization.
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- A strform attribute used in calls to __str__.
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- A call() method, which will make the actual execution call and must
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return a value to be held in the 'result' field of the job object."""
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# Class constants for status, in string and as numerical codes (when
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# updating jobs lists, we don't want to do string comparisons). This will
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# be done at every user prompt, so it has to be as fast as possible
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stat_created = 'Created'; stat_created_c = 0
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stat_running = 'Running'; stat_running_c = 1
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stat_completed = 'Completed'; stat_completed_c = 2
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stat_dead = 'Dead (Exception), call job.traceback() for details'
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stat_dead_c = -1
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def __init__(self):
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raise NotImplementedError, \
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"This class can not be instantiated directly."
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def _init(self):
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"""Common initialization for all BackgroundJob objects"""
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for attr in ['call','strform']:
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assert hasattr(self,attr), "Missing attribute <%s>" % attr
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# The num tag can be set by an external job manager
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self.num = None
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self.status = BackgroundJobBase.stat_created
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self.stat_code = BackgroundJobBase.stat_created_c
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self.finished = False
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self.result = '<BackgroundJob has not completed>'
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# reuse the ipython traceback handler if we can get to it, otherwise
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# make a new one
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try:
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self._make_tb = __IPYTHON__.InteractiveTB.text
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except:
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self._make_tb = AutoFormattedTB(mode = 'Context',
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color_scheme='NoColor',
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tb_offset = 1).text
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# Hold a formatted traceback if one is generated.
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self._tb = None
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threading.Thread.__init__(self)
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def __str__(self):
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return self.strform
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def __repr__(self):
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return '<BackgroundJob: %s>' % self.strform
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def traceback(self):
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print self._tb
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def run(self):
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try:
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self.status = BackgroundJobBase.stat_running
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self.stat_code = BackgroundJobBase.stat_running_c
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self.result = self.call()
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except:
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self.status = BackgroundJobBase.stat_dead
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self.stat_code = BackgroundJobBase.stat_dead_c
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self.finished = None
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self.result = ('<BackgroundJob died, call job.traceback() for details>')
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self._tb = self._make_tb()
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else:
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self.status = BackgroundJobBase.stat_completed
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self.stat_code = BackgroundJobBase.stat_completed_c
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self.finished = True
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class BackgroundJobExpr(BackgroundJobBase):
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"""Evaluate an expression as a background job (uses a separate thread)."""
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def __init__(self,expression,glob=None,loc=None):
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"""Create a new job from a string which can be fed to eval().
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global/locals dicts can be provided, which will be passed to the eval
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call."""
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# fail immediately if the given expression can't be compiled
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self.code = compile(expression,'<BackgroundJob compilation>','eval')
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if glob is None:
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glob = {}
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if loc is None:
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loc = {}
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self.expression = self.strform = expression
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self.glob = glob
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self.loc = loc
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self._init()
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def call(self):
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return eval(self.code,self.glob,self.loc)
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class BackgroundJobFunc(BackgroundJobBase):
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"""Run a function call as a background job (uses a separate thread)."""
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def __init__(self,func,*args,**kwargs):
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"""Create a new job from a callable object.
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Any positional arguments and keyword args given to this constructor
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after the initial callable are passed directly to it."""
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assert callable(func),'first argument must be callable'
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if args is None:
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args = []
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if kwargs is None:
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kwargs = {}
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self.func = func
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self.args = args
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self.kwargs = kwargs
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# The string form will only include the function passed, because
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# generating string representations of the arguments is a potentially
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# _very_ expensive operation (e.g. with large arrays).
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self.strform = str(func)
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self._init()
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def call(self):
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return self.func(*self.args,**self.kwargs)
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if __name__=='__main__':
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import time
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def sleepfunc(interval=2,*a,**kw):
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args = dict(interval=interval,
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args=a,
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kwargs=kw)
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time.sleep(interval)
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return args
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def diefunc(interval=2,*a,**kw):
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time.sleep(interval)
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die
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def printfunc(interval=1,reps=5):
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for n in range(reps):
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time.sleep(interval)
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print 'In the background...'
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jobs = BackgroundJobManager()
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# first job will have # 0
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jobs.new(sleepfunc,4)
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jobs.new(sleepfunc,kw={'reps':2})
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# This makes a job which will die
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jobs.new(diefunc,1)
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jobs.new('printfunc(1,3)')
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# after a while, you can get the traceback of a dead job. Run the line
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# below again interactively until it prints a traceback (check the status
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# of the job):
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print jobs[1].status
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jobs[1].traceback()
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# Run this line again until the printed result changes
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print "The result of job #0 is:",jobs[0].result
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