Printerface is an application that acts as a virtual printer, accepting LPD (Line Printer Daemon) documents and parses/renders them to PDF files. Documents are stored, searchable to users on your LAN using the build in web interface. Results can be browsed, emailed and automatically printed to modern network printers (anything with a CUPS/ppd driver). It has been used in production for over eight years by customers with legacy stock control/management systems, alarm pannels and fire pannels. Tea Engineering Ltd. provides commercial support and custom/integration services in the UK.
The service is written in Python, with a Javascript web front end using bootstrap JS. It has a rich JSON API and can be used as a centralised interface to legacy system output, whereby documents can be parsed and then consumed by downstream services. We have production instances with over 100k documents a year, 5-6M pages.
Computer systems as old as Windows NT4 can print to LPD printers as standard, so integration even into the most challenging environments is relatively easy compared to modifying legacy systems. Printerface provides a great path forward for customers trapped with old fixed-width, fanfold or pre-printed stationary systems, or struggling to maintain old dot-matrix line printers.
Often we can de-duplicate or drop entirely sections of the documents that are no longer required in hard copies, to reduce the environmental footprint of legacy print jobs.
The following will checkout the source code, build a docker image and start an instance of printerface on localhost. The web interface listens on http://localhost:8081 ands the LPR printing endpoint will be running on tcp port 515. These steps roughly work on mac, linux and windows.
$ git clone git@github.com:shuckc/printerface.git
$ cd printerface
$ docker build -t printerface:latest .
$ docker create --name p1 -p 8081:8081 -p 515:1515 printerface
$ docker start p1
lpdserver.pyimplements a UNIX LPD daemon for recieving print jobshttpserver.pysimple http server using asynchatmailer.pyasynchronous mail queue to Gmaildocparserrecognise and parse some plain-text formats from 1990 to JSONstationary.pyformat JSON to nice PDF filesprinting.pyLinux printing with CUPS via. command line
Requirements are specified in requirements.txt
Unit tests run during docker build or with:
$ python -m unittest discover --pattern=*.py
Uses python asyncore/smtp, bootstrap web framework
The Dockfile fully describes how to build a containerised printerface, including dependancies.
$ git clone git@github.com:shuckc/printerface.git
$ cd printerface
$ docker build .
The built docker image does not appear on disk as a file, but is incorporated into docker's 'image repository'. To be able to use the docker image, you must tag it. For instance, build and tag like this:
$ docker build -t printerface:latest .
If you wish to start a container locally, then you create a container, specifying the tagged image and provide the environment variables needed to start up successfully. You can do this as below:
docker create --name p1 -p 8081:8081 -p 515:1515 printerface
docker start p1
Note that the image is resolved permimently to a hash of some sort at this point. If you re-build and update the tag, you still need to throw away the container and recreate it.
docker stop p1
docker rm p1
On windows you may wish to mount the job storage directory externally, as follows:
docker create --rm --name p1 -p 8081:8081 -p 515:1515 -v c:/Users/cshucks/printerface:/root/printerface printerface
$ mkdir ~/opt
$ wget https://www.python.org/ftp/python/2.7.18/Python-2.7.18.tgz
$ tar -xzf Python-2.7.18.tgz
$ cd Python-2.7.18
$ ./configure prefix=$HOME/opt --with-ensurepip=install
$ make && make install
$ ~/opt/bin/pip install -r ~/repos/printerface/requirements.txt