#!/usr/bin/env python
# coding: utf-8

# # Simple interactive bacgkround jobs with IPython
# 
# We start by loading the `backgroundjobs` library and defining a few trivial functions to illustrate things with.

# In[1]:


from IPython.lib import backgroundjobs as bg

import sys
import time

def sleepfunc(interval=2, *a, **kw):
    args = dict(interval=interval,
                args=a,
                kwargs=kw)
    time.sleep(interval)
    return args

def diefunc(interval=2, *a, **kw):
    time.sleep(interval)
    raise Exception("Dead job with interval %s" % interval)

def printfunc(interval=1, reps=5):
    for n in range(reps):
        time.sleep(interval)
        print('In the background... %i' % n)
        sys.stdout.flush()
    print('All done!')
    sys.stdout.flush()


# Now, we can create a job manager (called simply `jobs`) and use it to submit new jobs.
# 
# Run the cell below, it will show when the jobs start. Wait a few seconds until you see the 'all done' completion message:

# In[2]:


jobs = bg.BackgroundJobManager()

# Start a few jobs, the first one will have ID # 0
jobs.new(sleepfunc, 4)
jobs.new(sleepfunc, kw={'reps':2})
jobs.new('printfunc(1,3)')


# You can check the status of your jobs at any time:

# In[3]:


jobs.status()


# For any completed job, you can get its result easily:

# In[4]:


jobs[0].result


# ## Errors and tracebacks

# The jobs manager tries to help you with debugging:

# In[5]:


# This makes a couple of jobs which will die.  Let's keep a reference to
# them for easier traceback reporting later
diejob1 = jobs.new(diefunc, 1)
diejob2 = jobs.new(diefunc, 2)


# You can get the traceback of any dead job.  Run the line
# below again interactively until it prints a traceback (check the status
# of the job):
# 

# In[6]:


print("Status of diejob1: %s" % diejob1.status)
diejob1.traceback()  # jobs.traceback(4) would also work here, with the job number


# This will print all tracebacks for all dead jobs:

# In[7]:


jobs.traceback()


# The job manager can be flushed of all completed jobs at any time:

# In[8]:


jobs.flush()


# After that, the status is simply empty:

# In[9]:


jobs.status()


# Jobs have a `.join` method that lets you wait on their thread for completion:

# In[10]:


j = jobs.new(sleepfunc, 2)
get_ipython().run_line_magic('pinfo', 'j.join')


# ## Exercise
# 
# 1. Start a new job that calls `sleepfunc` with a 5-second wait
# 2. Print a short message that indicates you are waiting (note: you'll need to flush stdout to see that print output appear).
# 3. Wait on the job and then print its result.