2023-04-22: Archiving this code.

Background
----------

This is an entry in the Ducksboard Hackathon.  See the live dashboard at:
    https://public.ducksboard.com/4p2wevyDlQBlTFeui_Q5/

UPDATE: and it won! Thanks guys!
    http://blog.ducksboard.com/2011/11/announcing-the-hackathon-results/

Streamfeed sends information about streams- the physical, wet kind- to
the Ducksboard API.  Its primary data source is the USGS Water Services
API (http://waterservices.usgs.gov/), which provides a flexible API to
various data from thousands of deployed sensors.

But, hydrologists (probably?) are already able to analyze this data in a
more sophisticated way than using Ducksboard, right?  Right.  But this
information- realtime and recent- is also of interest to other people.

Whitewater kayakers need to know what streams and rivers are runnable 
(able to be be navigated at an acceptable/desired level of risk) in
enough time to get to a launch site with a boat.  Preferably with some
other people, and a couple of vehicles.  Knowing what the river is doing
now- combined with a weather forecast and some social networking- makes
this an easier task.

Technical Details
-----------------

Here's a application written in Go (http://golang.org) that updates
Ducksboard widgets with images and USGS gauge information.  It can be
configured via a JSON configuration file to query / update other USGS 
sensors as required.

To compile:
    cd ducksboard
    gomake
    cd ..
    gomake

To run:
    edit config.json, inserting your Ducksboard API key
    ./streamfeeder -f config.json


A couple of notes:

* The app runs in the foreground, sleeping for the number of seconds
defined by the "refresh" configuration setting then re-querying sources. 
If this parameter is less than 60 then the app will exit after a single 
run- allowing it to be run from cron or similar if desired.

* A single HTTP call is made to the USGS API, and the response includes
information for all the sensors / types of data (discharge, depth, etc)
defined in the configuration file.

* Calls to the Ducksboard API are handled by a small pool of HTTP
connections.  The pool size is a constant, MAX_PUSH_CONNECTIONS, defined
in config.go, currently set to 4. And since Ducksboard supports HTTP keep-
alives only 4 TCP connections will be used.

* I used the Go release weekly.2011-11-02 for development.  A change
with error handling just occurred ("os.Error" is now "error"), so if you
want to compile this with an older version of Go, you'll have to address
that.