Simple asynchronous job queue via redis.
Rotterdam is an asynchronous job queue system written in Python with a dab of Lua, designed with simplicty and ease of use in mind with as few dependencies as possible.
Rotterdam is available via pypi, installing for clients is as easy as:
pip install rotterdam
To use the server scripts, install the “server” subproject:
pip install rotterdam[server]
Make sure to have a redis instance version 2.6 or newer at the location specified in your config file under the arbiter section. See the example.cfg file for an example.
To start the rotterdam server, run the rotterdam executable and pass in the location of a config file (an example.cfg is included in this here repo):
[ ~ ] $ rotterdam example.cfg INFO:rotterdam.master:Starting master (52174) INFO:rotterdam.master:Listening on port 8765 INFO:rotterdam.master:Starting up consumer INFO:rotterdam.master:Starting up consumer
All a client program has to do is instantiate a Rotterdam class with the proper host and port and call enqueue:
from rotterdam import Rotterdam client = Rotterdam("localhost") # default port is 8765 client.enqueue("rotterdam.example:some_job", "thingy", "guy", foo="bar") client.enqueue("rotterdam.example:some_job", "derp", "hork", foo="bazz")
The first argument to enqueue can either be an instance of a function, or a string with the full namespace of the function to be run.
In this example, the job is a simple function that prints out its own arguments:
import time def some_job(arg1, arg2, foo=None): time.sleep(2) print "arg1: %s" % arg1 print "arg2: %s" % arg2 print "foo: %s" % foo
So once the client program is run the rotterdam process will print out the args on its end:
arg1: derp arg2: hork foo: bazz arg1: thingy arg2: guy foo: bar
Note that since it’s jobs are executed _concurrently_ with consumer processes they don’t necessarily execute in the same order the client sends them.
Rotterdam uses inter-process communcation (IPC) signals for most tasks so that the master/worker processes can chug along the whole time without needed to be restarted. The rotterdamctl program is a handy utility for sending the proper signals to the proper process. This program also takes the location of a config file as the first argument. Make sure to use the same config file as the rotterdam process you want to control!
To add a consumer to the existing rotterdam processes, pass the expand command to rotterdamctl.:
[ ~ ] $ rotterdamctl example.cfg expand
The master processes will log that a new consumer is added:
INFO:rotterdam.master:Upping number of consumers to 3 INFO:rotterdam.master:Starting up consumer
Contracting the number of consumers is a similiar process, but with the contract command:
[ ~ ] $ rotterdamctl example.cfg contract INFO:rotterdam.master:Contracting number of consumers to 2 INFO:rotterdam.master:Consumer exiting
The rotterdam master process has a facility for reloading its config file on-the-fly so no work is lost. It is invoked with the reload command to rotterdamctl.:
[ ~ ] $ rotterdamctl example.cfg reload
The master process will then re-read the config file and signal each worker process to wrap up whatever it’s doing while at the same time spawning new worker processes based on the new config.:
INFO:rotterdam.master:Reloading config INFO:rotterdam.master:Starting up consumer INFO:rotterdam.master:Starting up consumer INFO:rotterdam.master:Consumer exiting INFO:rotterdam.master:Consumer exiting
Naturally, rotterdam only knows of the jobs available to its python runtime. What to do when you update the code to have shiny new jobs, but you don’t want to shut down or pause any work while updating? For this case there’s the relaunch command:
[ ~ ] $ rotteramctl example.cfg relaunch
The master process will spawn a new master with the same arguments it was invoked with and passes along the listening socket’s file descriptor.:
INFO:rotterdam.master:Winding down old master INFO:rotterdam.master:Starting master (52580) INFO:rotterdam.master:Listening on port 8765 INFO:rotterdam.master:Starting up consumer INFO:rotterdam.master:Starting up consumer INFO:rotterdam.master:Consumer exiting INFO:rotterdam.master:Consumer exiting [ ~ ] $
Once the new master is up and running, the old master process signals its child worker processes to wrap up what they’re doing and shuts itself down while the new master processes chugs along and accepts data on the same socket but with freshly-loaded python code.
Stopping rotterdam is done via the stop command:
[ ~ ] $ rotterdamctl example.cfg stop INFO:rotterdam.master:Winding down master INFO:rotterdam.master:Consumer exiting INFO:rotterdam.master:Consumer exiting
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