A CKAN extension containinig plugins
First is used by http://catalog.data.gov/ to harvest data sources
from a remote /data.json file according to the U.S. Project
Open Data metadata specification (https://project-open-data.cio.gov/).
datajson provides a harvester to import datasets from other
remote /data.json files. See below for setup instructions.
And the plugin also provides a new view to validate /data.json files at http://ckanhostname/pod/validate.
To install, activate your CKAN virtualenv, install dependencies, and install the module in develop mode, which just puts the directory in your Python path.
. path/to/pyenv/bin/activate pip install -r pip-requirements.txt python setup.py develop
Then in your CKAN .ini file, add
to your ckan.plugins line:
ckan.plugins = (other plugins here...) datajson
That's the plugin for /data.json output. To make the harvester available, also add:
ckan.plugins = (other plugins here...) harvest datajson_harvest
If you're running CKAN via WSGI, we found a strange Python dependency bug. It might only affect development environments. The fix was to revise wsgi.py and add:
from paste.deploy import loadapp
Then restart your server and check out:
http://yourdomain.com/data.json and http://yourdomain.com/data.jsonld and http://yourdomain.com/pod/validate
Caching The Response
If you're deploying inside Apache, some caching would be a good idea because generating the /data.json file can take a good few moments. Enable the cache modules:
a2enmod cache a2enmod disk_cache
And then in your Apache configuration add:
CacheEnable disk /data.json CacheRoot /tmp/apache_cache CacheDefaultExpire 120 CacheMaxFileSize 50000000 CacheIgnoreCacheControl On CacheIgnoreNoLastMod On CacheStoreNoStore On
And be sure to create /tmp/apache_cache and make it writable by the Apache process.
Generating /data.json Off-Line
Generating this file is a little slow, so an alternative instead of caching is to generate the file periodically (e.g. in a cron job). In that case, you'll want to change the path that CKAN generates the file at to something other than /data.json. In your CKAN .ini file, in the app:main section, add:
ckanext.datajson.path = /internal/data.json
Now create a crontab file ("mycrontab") to download this URL to a file on disk every ten minutes:
0-59/10 * * * * wget -qO /path/to/static/data.json http://localhost/internal/data.json
And activate your crontab like so:
In Apache, we'll want to block outside access to the "internal" URL, and also map the URL /data.json to the static file. In your httpd.conf, add:
Alias /data.json /path/to/static/data.json <Location /internal/> Order deny,allow Allow from 127.0.0.1 Deny from all </Location>
And then restart Apache. Wait for the cron job to run once, then check if /data.json loads (and it should be fast!). Also double check that http://yourdomain.com/internal/data.json gives a 403 forbidden error when accessed from some other location.
You can customize the URL that generates the data.json output:
ckanext.datajson.path = /data.json ckanext.datajsonld.path = /data.jsonld ckanext.datajsonld.id = http://www.youragency.gov/data.json
You can enable or disable the Data.json output by setting
ckanext.datajson.url_enabled = False
If ckanext.datajsonld.path is omitted, it defaults to replacing ".json" in your ckanext.datajson.path path with ".jsonld", so it probably won't need to be specified.
The option ckanext.datajsonld.id is the @id value used to identify the data catalog itself. If not given, it defaults to ckan.site_url.
To use the data.json harvester, you'll also need to set up the CKAN harvester extension. See the CKAN harvester README at https://github.com/okfn/ckanext-harvest for how to do that. You'll set some configuration variables and then initialize the CKAN harvester plugin using:
paster --plugin=ckanext-harvest harvester initdb --config=/path/to/ckan.ini
Now you can set up a new DataJson harvester by visiting:
And when configuring the data source, just choose "/data.json" as the source type.
The next paragraph assumes you're using my fork of the CKAN harvest extension at https://github.com/JoshData/ckanext-harvest
In the configuration field, you can put a YAML string containing defaults for fields that may not be set in the source data.json files, e.g. enter something like this:
defaults: Agency: Department of Health & Human Services Author: Substance Abuse & Mental Health Services Administration author_id: http://healthdata.gov/id/agency/samhsa
This again is tied to the HealthData.gov metadata schema.
Credit / Copying
Original work written by the HealthData.gov team. It has been modified in support of Data.gov.
As a work of the United States Government, this package is in the public domain within the United States. Additionally, we waive copyright and related rights in the work worldwide through the CC0 1.0 Universal public domain dedication (which can be found at http://creativecommons.org/publicdomain/zero/1.0/).