rotterdam 0.5.2

Simple asynchronous job queue via redis.

Rotterdam
=========

[](https://travis-ci.org/wglass/rotterdam) [](https://codeclimate.com/github/wglass/rotterdam)

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.


It uses [redis](http://redis.io/) as its datastore and is heavily inspired by the [unicorn](http://unicorn.bogomips.org)
and [gunicorn](https://github.com/benoitc/gunicorn) master/worker process model.

**[Installation](#installation)**
**[Usage](#usage)**
**[Starting up](#starting-up)**
**[Sending jobs](#sending-jobs)**
**[Controlling the master process](#controlling-the-master-process)**
**[Controlling the number of consumers](#controlling-the-number-of-consumers)**
**[Reloading configuration settings](#reloading-configuration-settings)**
**[Reloading new code](#reloading-new-code)**
**[Shutting down](#shutting-down)**
**[License](#license)**

## Installation

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]
```

## Usage
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.

### Starting up
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
```

### Sending jobs
All a client program has to do is instantiate a `Rotterdam` class with the proper host
and port and call `enqueue`:
```python
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:
```python
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.

### Controlling the master process
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!

### Controlling the number of consumers
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
```
### Reloading configuration settings
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
```
### Reloading new code
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.

### Shutting down
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
```

## License

(c) 2013-2015 William Glass

Rotterdam licensed under the terms of the MIT license. See the
[LICENSE](https://github.com/wglass/rotterdam/blob/master/README.md) file for more details.