uWSGI API - Python decorators¶
The uWSGI API is very low-level, as it must be language-independent.
That said, being too low-level is not a Good Thing for many languages, such as Python.
Decorators are, in our humble opinion, one of the more kick-ass features of Python, so in the uWSGI source tree you will find a module exporting a bunch of decorators that cover a good part of the uWSGI API.
Notes¶
Signal-based decorators execute the signal handler in the first available worker.
If you have enabled the spooler you can execute the signal handlers in it, leaving workers free to manage normal requests. Simply pass target='spooler'
to the decorator.
@timer(3, target='spooler')
def hello(signum):
print("hello")
Example: a Django session cleaner and video encoder¶
Let’s define a task.py
module and put it in the Django project directory.
from uwsgidecorators import *
from django.contrib.sessions.models import Session
import os
@cron(40, 2, -1, -1, -1)
def clear_django_session(num):
print("it's 2:40 in the morning: clearing django sessions")
Session.objects.all().delete()
@spool
def encode_video(arguments):
os.system("ffmpeg -i \"%s\" image%%d.jpg" % arguments['filename'])
The session cleaner will be executed every day at 2:40, to enqueue a video encoding we simply need to spool it from somewhere else.
from task import encode_video
def index(request):
# launching video encoding
encode_video.spool(filename=request.POST['video_filename'])
return render_to_response('enqueued.html')
Now run uWSGI with the spooler enabled:
[uwsgi]
; a couple of placeholder
django_projects_dir = /var/www/apps
my_project = foobar
; chdir to app project dir and set pythonpath
chdir = %(django_projects_dir)/%(my_project)
pythonpath = %(django_projects_dir)
; load django
module = django.core.handlers:WSGIHandler()
env = DJANGO_SETTINGS_MODULE=%(my_project).settings
; enable master
master = true
; 4 processes should be enough
processes = 4
; enable the spooler (the mytasks dir must exist!)
spooler = %(chdir)/mytasks
; load the task.py module
import = task
; bind on a tcp socket
socket = 127.0.0.1:3031
The only especially relevant option is the import
one. It works in the same way as module
but skips the WSGI callable search.
You can use it to preload modules before the loading of WSGI apps. You can specify an unlimited number of ‘’’import’’’ directives.
Example: web2py + spooler + timer¶
First of all define your spooler and timer functions (we will call it :file:mytasks.py
)
from uwsgidecorators import *
@spool
def a_long_task(args):
print(args)
@spool
def a_longer_task(args)
print("longer.....")
@timer(3)
def three_seconds(signum):
print("3 seconds elapsed")
@timer(10, target='spooler')
def ten_seconds_in_the_spooler(signum):
print("10 seconds elapsed in the spooler")
Now run web2py.
uwsgi --socket :3031 --spooler myspool --master --processes 4 --import mytasks --module web2py.wsgihandler
As soon as the application is loaded, you will see the 2 timers running in your logs.
Now we want to enqueue tasks from our web2py controllers.
Edit one of them and add
import mytasks # be sure mytasks is importable!
def index(): # this is a web2py action
mytasks.a_long_task.spool(foo='bar')
return "Task enqueued"
uwsgidecorators API reference¶
- uwsgidecorators.postfork(func)¶
uWSGI is a preforking (or “fork-abusing”) server, so you might need to execute a fixup task after each
fork()
. Thepostfork
decorator is just the ticket. You can declare multiplepostfork
tasks. Each decorated function will be executed in sequence after eachfork()
.@postfork def reconnect_to_db(): myfoodb.connect() @postfork def hello_world(): print("Hello World")
- uwsgidecorators.spool(func, pass_arguments=False)¶
The uWSGI spooler can be very useful. Compared to Celery or other queues it is very “raw”. The
spool
decorator will help!@spool def a_long_long_task(arguments): print(arguments) for i in xrange(0, 10000000): time.sleep(0.1) @spool def a_longer_task(args): print(args) for i in xrange(0, 10000000): time.sleep(0.5) # enqueue the tasks a_long_long_task.spool(foo='bar', hello='world') a_longer_task.spool({'pippo':'pluto'})
Warning
On Python3, only
bytes
type arguments are allowed. See below for another way of passing arguments.When
pass_arguments
is set toTrue
, arguments can be of any type supported by thepickle
module. The following arguments have a special meaning:spooler
: specify the absolute path of the spooler that has to manage this taskat
: unix time at which the task must be executed (read: the task will not be run until theat
time is passed)priority
: this will be the subdirectory in the spooler directory in which the task will be placed, you can use that trick to give a good-enough prioritization to tasks (for better approach use multiple spoolers)
Warning
On Python3, the special arguments
spooler
,at
,priority
andbody
must bebytes
.@spool(pass_arguments=True) def some_task(*args, **kwargs): print(args) print(kwargs) for i in xrange(0, 10000000): time.sleep(0.5) # enqueue the task some_task.spool(id=42, foo=['bar', 'baz'], func=min, at=str(1497023151))
The functions will automatically return
uwsgi.SPOOL_OK
so they will be executed one time independently by their return status.
- uwsgidecorators.spoolforever(func, pass_arguments=False)¶
Use
spoolforever
when you want to continuously execute a spool task. A@spoolforever
task will always returnuwsgi.SPOOL_RETRY
.@spoolforever def a_longer_task(args): print(args) for i in xrange(0, 10000000): time.sleep(0.5) # enqueue the task a_longer_task.spool({'pippo':'pluto'})
Warning
On Python3, only
bytes
type arguments are allowed. See below for another way of passing arguments.When
pass_arguments
is set toTrue
, arguments can be of any type supported by thepickle
module. The following arguments have a special meaning:spooler
: specify the absolute path of the spooler that has to manage this taskat
: unix time at which the task must be executed (read: the task will not be run until theat
time is passed)priority
: this will be the subdirectory in the spooler directory in which the task will be placed, you can use that trick to give a good-enough prioritization to tasks (for better approach use multiple spoolers)
Warning
On Python3, the special arguments
spooler
,at
,priority
andbody
must bebytes
.@spoolforever(pass_arguments=True) def a_longer_task(*args): print(args) for i in xrange(0, 10000000): time.sleep(0.5) # enqueue the task a_longer_task.spool('pluto', 42)
- uwsgidecorators.spoolraw(func, pass_arguments=False)¶
Advanced users may want to control the return value of a task.
@spoolraw def a_controlled_task(args): if args['foo'] == 'bar': return uwsgi.SPOOL_OK return uwsgi.SPOOL_RETRY a_controlled_task.spool(foo='bar')
Warning
On Python3, only
bytes
type arguments are allowed. See below for another way of passing arguments.When
pass_arguments
is set toTrue
, arguments can be of any type supported by thepickle
module. The following arguments have a special meaning:spooler
: specify the absolute path of the spooler that has to manage this taskat
: unix time at which the task must be executed (read: the task will not be run until theat
time is passed)priority
: this will be the subdirectory in the spooler directory in which the task will be placed, you can use that trick to give a good-enough prioritization to tasks (for better approach use multiple spoolers)
Warning
On Python3, the special arguments
spooler
,at
,priority
andbody
must bebytes
.@spoolraw(pass_arguments=True) def a_controlled_task(**kwargs): if kwargs['foo'] == 'bar': return uwsgi.SPOOL_OK return uwsgi.SPOOL_RETRY a_controlled_task.spool(foo='bar', age=42)
- uwsgidecorators.rpc("name", func)¶
uWSGI uWSGI RPC Stack is the fastest way to remotely call functions in applications hosted in uWSGI instances. You can easily define exported functions with the @rpc decorator.
@rpc('helloworld') def ciao_mondo_function(): return "Hello World"
- uwsgidecorators.signal(num)(func)¶
You can register signals for the signal framework in one shot.
@signal(17) def my_signal(num): print("i am signal %d" % num)
- uwsgidecorators.timer(interval, func)¶
Execute a function at regular intervals.
@timer(3) def three_seconds(num): print("3 seconds elapsed")
- uwsgidecorators.rbtimer(interval, func)¶
Works like @timer but using red black timers.
- uwsgidecorators.cron(min, hour, day, mon, wday, func)¶
Easily register functions for the CronInterface.
@cron(59, 3, -1, -1, -1) def execute_me_at_three_and_fiftynine(num): print("it's 3:59 in the morning")
Since 1.2, a new syntax is supported to simulate
crontab
-like intervals (every Nth minute, etc.).*/5 * * * *
can be specified in uWSGI like thus:@cron(-5, -1, -1, -1, -1) def execute_me_every_five_min(num): print("5 minutes, what a long time!")
- uwsgidecorators.filemon(path, func)¶
Execute a function every time a file/directory is modified.
@filemon("/tmp") def tmp_has_been_modified(num): print("/tmp directory has been modified. Great magic is afoot")
- uwsgidecorators.erlang(process_name, func)¶
Map a function as an Erlang process.
@erlang('foobar') def hello(): return "Hello"
- uwsgidecorators.thread(func)¶
Mark function to be executed in a separate thread.
Important
Threading must be enabled in uWSGI with the
enable-threads
orthreads <n>
option.@thread def a_running_thread(): while True: time.sleep(2) print("i am a no-args thread") @thread def a_running_thread_with_args(who): while True: time.sleep(2) print("Hello %s (from arged-thread)" % who) a_running_thread() a_running_thread_with_args("uWSGI")
You may also combine
@thread
with@postfork
to spawn the postfork handler in a new thread in the freshly spawned worker.@postfork @thread def a_post_fork_thread(): while True: time.sleep(3) print("Hello from a thread in worker %d" % uwsgi.worker_id())
- uwsgidecorators.lock(func)¶
This decorator will execute a function in fully locked environment, making it impossible for other workers or threads (or the master, if you’re foolish or brave enough) to run it simultaneously. Obviously this may be combined with @postfork.
@lock def dangerous_op(): print("Concurrency is for fools!")
- uwsgidecorators.mulefunc([mulespec, ]func)¶
Offload the execution of the function to a mule. When the offloaded function is called, it will return immediately and execution is delegated to a mule.
@mulefunc def i_am_an_offloaded_function(argument1, argument2): print argument1,argument2
You may also specify a mule ID or mule farm to run the function on. Please remember to register your function with a uwsgi import configuration option.
@mulefunc(3) def on_three(): print "I'm running on mule 3." @mulefunc('old_mcdonalds_farm') def on_mcd(): print "I'm running on a mule on Old McDonalds' farm."
- uwsgidecorators.harakiri(time, func)¶
Starting from uWSGI 1.3-dev, a customizable secondary harakiri subsystem has been added. You can use this decorator to kill a worker if the given call is taking too long.
@harakiri(10) def slow_function(foo, bar): for i in range(0, 10000): for y in range(0, 10000): pass # or the alternative lower level api uwsgi.set_user_harakiri(30) # you have 30 seconds. fight! slow_function() uwsgi.set_user_harakiri(0) # clear the timer, all is well