"Can't start a new thread error" in Python

Question

I am running a script which extracts the information from debian packages and saves it in a database.

After extracting information from about 100 packages an error occurs. The error is "can't start a new thread" Why am I facing this error? What can be the possible solution to it?

This is the code used to save the data :

for i in list_pack:

      if not i in oblist:        
        #Creating Packages
            slu=slugify(i)
            ob=Gbobject()
            ob.title=i
            ob.slug=slu
            ob.content=''
            ob.tags=tagname
        #with reversion.create_revision():
            ob.save()
            gb=Gbobject.objects.get(title=i)
            gb.objecttypes.add(Objecttype.objects.get(title='Packages'))
            gb.sites.add(Site.objects.get_current())
        #with reversion.create_revision():
            gb.save()
            gd=Gbobject.objects.get(title=i)
            print 'The Object created was',gd


            #Decsription
            try:
                atv=package_description_dict[i]
                atvalue=unicode(atv,'utf-8')
            except UnicodeDecodeError:
                pass
            try:
                lo=Gbobject.objects.get(title=i)
                loid=NID.objects.get(id=lo.id)
            except Gbobject.DoesNotExist:
                pass
            if atvalue<>'':
                slu=slugify(atvalue)
                at=Attribute()
                at.title=atvalue
                at.slug=slu
                at.svalue=atvalue
                at.subject=loid
                att=Attributetype.objects.get(title='Description')
                at.attributetype=att
                #with reversion.create_revision():
                at.save()                    
                print 'yeloow13'

Just like Description, there are around !2 more properties of the package which are saved in a similar way.

This is the full traceback that I get when the error occurs :-

    error                                     Traceback (most recent call last)

/home/radhika/Desktop/dev_75/gnowsys-studio/demo/<ipython console> in <module>()

/usr/local/lib/python2.6/dist-packages/django_gstudio-0.3.dev-py2.6.egg/gstudio/Harvest/debdata.py in <module>()
   1086 # create_attribute_type()

   1087 # create_relation_type()

-> 1088 create_objects()
   1089 #create_sec_objects()

   1090 #create_relations()


/usr/local/lib/python2.6/dist-packages/django_gstudio-0.3.dev-py2.6.egg/gstudio/Harvest/debdata.py in create_objects()
    403             ob.sites.add(Site.objects.get_current())
    404             #with reversion.create_revision():

--> 405             ob.save()
    406             #time.sleep(10)

    407             #gd=Gbobject.objects.get(title=i)


/usr/local/lib/python2.6/dist-packages/django_reversion-1.6.0-py2.6.egg/reversion/revisions.pyc in do_revision_context(*args, **kwargs)
    298             try:
    299                 try:
--> 300                     return func(*args, **kwargs)
    301                 except:
    302                     exception = True

/usr/local/lib/python2.6/dist-packages/django_gstudio-0.3.dev-py2.6.egg/objectapp/models.pyc in save(self, *args, **kwargs)
    658     @reversion.create_revision()
    659     def save(self, *args, **kwargs):
--> 660         super(Gbobject, self).save(*args, **kwargs) # Call the "real" save() method.
    661 
    662 

/usr/local/lib/python2.6/dist-packages/django_reversion-1.6.0-py2.6.egg/reversion/revisions.pyc in do_revision_context(*args, **kwargs)
    298             try:
    299                 try:
--> 300                     return func(*args, **kwargs)
    301                 except:
    302                     exception = True

/usr/local/lib/python2.6/dist-packages/django_gstudio-0.3.dev-py2.6.egg/gstudio/models.pyc in save(self, *args, **kwargs)
    327     @reversion.create_revision()
    328     def save(self, *args, **kwargs):
--> 329         super(Node, self).save(*args, **kwargs) # Call the "real" save() method.
    330 
    331 

/usr/local/lib/python2.6/dist-packages/django/db/models/base.pyc in save(self, force_insert, force_update, using)
    458         if force_insert and force_update:
    459             raise ValueError("Cannot force both insert and updating in model saving.")
--> 460         self.save_base(using=using, force_insert=force_insert, force_update=force_update)
    461 
    462     save.alters_data = True

/usr/local/lib/python2.6/dist-packages/django/db/models/base.pyc in save_base(self, raw, cls, origin, force_insert, force_update, using)
    568         if origin and not meta.auto_created:
    569             signals.post_save.send(sender=origin, instance=self,
--> 570                 created=(not record_exists), raw=raw, using=using)
    571 
    572 

/usr/local/lib/python2.6/dist-packages/django/dispatch/dispatcher.pyc in send(self, sender, **named)
    170 
    171         for receiver in self._live_receivers(_make_id(sender)):
--> 172             response = receiver(signal=self, sender=sender, **named)
    173             responses.append((receiver, response))
    174         return responses

/usr/local/lib/python2.6/dist-packages/django_gstudio-0.3.dev-py2.6.egg/objectapp/signals.pyc in wrapper(*args, **kwargs)
     65             if inspect.getmodulename(fr[1]) == 'loaddata':
     66                 return
---> 67         signal_handler(*args, **kwargs)
     68 
     69     return wrapper

/usr/local/lib/python2.6/dist-packages/django_gstudio-0.3.dev-py2.6.egg/objectapp/signals.pyc in ping_external_urls_handler(sender, **kwargs)
     90         from objectapp.ping import ExternalUrlsPinger
     91 
---> 92         ExternalUrlsPinger(gbobject)
     93 
     94 

/usr/local/lib/python2.6/dist-packages/django_gstudio-0.3.dev-py2.6.egg/objectapp/ping.pyc in __init__(self, gbobject, timeout, start_now)
    153         threading.Thread.__init__(self)
    154         if start_now:
--> 155             self.start()
    156 
    157     def run(self):

/usr/lib/python2.6/threading.pyc in start(self)
    472         _active_limbo_lock.release()
    473         try:
--> 474             _start_new_thread(self.__bootstrap, ())
    475         except Exception:
    476             with _active_limbo_lock:

error: can't start new thread

I am not writing any code to handle the threads.

Answer 1

Sorry to have an incomplete solution here, I don't have the rating to post in the comment section.

One thing to check is the total number of threads you have running. I have some code that checks the count of cores (with sys) and then launches threads and checks core loading to test how the OS handles thread distribution and I've learned that windows 7 (for example) seems to throw an error beyond 32 threads on an 8 (logical) core CPU. [That's on Python 2.7, 32 bit within Win 7 64-bit, etc, YMMMV]. On other machines I can get past 1,000 Threads.

So I guess the short version is: how many threads do you already have going when you get that error? You can check with

threading.active_count()

Beyond that you don't really give the threading part of the code here so I'd direct you to this excellent Python Central page.

You may also benefit from this previous Stack overflow discussion on large thread task counts and how to approach them.

Again, my apologies that this is more of a direction to look than a solution, I think that more information is likely needed to help us understand what you're running into.