# python_pinger

These are different approaches to how one might implement a daemon to
repeatedly ping multiple hosts to see if the network is up.

## Single Threaded

This is the most naive implementation. For each ping host, the main
process thread pings them one at a time, and prints any changes.

![Single Threaded Pings](http://git.dlma.com/python_pinger.git/blob/master/images/ping_single_threaded.png)

### Upsides

Really simple code.

### Downsides

Since the pings are serialized, one long timeout from one host could
affect detecting a problem at another host.

## Long Lived Workers Consuming from Queue

Raymond Hettinger's [PyBay 2018 Keynote](https://pybay.com/site_media/slides/raymond2017-keynote/threading.html)
uses the queue module to send data between threads, so I thought I'd make a version of the pinger that did the same.

[long\_lived\_worker\_queue.py](http://git.dlma.com/python_pinger.git/blob/master/long_lived_worker_queue.py)

![Long Lived Queue Workers](http://git.dlma.com/python_pinger.git/blob/master/images/ping_long_lived_queue_workers.png)

### Upsides

Multi-threaded ping calls won't block each other.

### Downsides

The ping tasks read from, and write to a shared dictionary. (Reading and updating the last status.)

## Short Lived Workers

![Short Lived Workers](http://git.dlma.com/python_pinger.git/blob/master/images/ping_short_lived_workers.png)

[short\_lived\_workers.py](http://git.dlma.com/python_pinger.git/blob/master/short_lived_workers.py)

### Upsides

The worker tasks aren't in memory if they're not doing anything. So usually a smaller memory profile.

### Downsides

The ping tasks still read from, and write to a shared dictionary. (Reading and updating the last status.)

## Long Lived Looping Workers

![Long Lived Looping Workers](http://git.dlma.com/python_pinger.git/blob/master/images/ping_long_lived_looping_workers.png)

[long\_lived\_looping\_workers.py](http://git.dlma.com/python_pinger.git/blob/master/long_lived_looping_workers.py)

### Upsides

No more race conditions! The worker threads mind their own business.

### Downsides

The worker threads remain in memory.

## Is it any good?

[Yes](https://news.ycombinator.com/item?id=3067434).

## Licence

This software uses the [MIT license](http://git.dlma.com/python_pinger.git/blob/master/LICENSE.txt).