The CKAN Archiver Extension will download CKAN resources. It runs as a Celery
process, and takes instructions from a queue to download each resource. These
instructions can come from:
1. CKAN every time a resources that are added
2. the command line
Many Archiver processes can be started to run in parallel, all using the same
queue.
The CKAN Archiver Extension will download all of a CKAN's resources, for three purposes:
1. offer the user it as a 'cached' copy, in case the link becomes broken
2. tell the user (and publishers) if the link is broken, on both the dataset/resource and in a 'Broken Links' report
3. the downloaded file can be analysed by other extensions, such as ckanext-qa or ckanext-pacakgezip.
Demo:
.. image:: archiver_resource.png
:alt: Broken link check info and a cached copy offered on resource
.. image:: archiver_report.png
:alt: Broken link report
Compatibility: Requires CKAN version 2.1 or later
TODO:
* Show brokenness on the package page (not just the resources)
* Prettify the html bits
* Add brokenness to search facets using IFacet
Operation
---------
When a resource is archived, the information about the archival - if it failed, the filename on disk, file size etc - is stored in the Archival table. (In ckanext-archiver v0.1 it was stored in TaskStatus and on the Resource itself.) This is added to dataset during the package_show call (using a schema key), so the information is also available over the API.
Other extensions can subscribe to the archiver's ``IPipe`` interface to hear about datasets being archived. e.g. ckanext-qa will detect its file type and give it an openness score, or ckanext-packagezip will create a zip of the files in a dataset.
Archiver works on Celery queues, so when Archiver is notified of a dataset/resource being created or updated, it puts an 'update request' on a queue. Celery calls the Archiver 'update task' to do each archival. You can start Celery with multiple processes, to archive in parallel.
You can also trigger an archival using paster on the command-line.
By default, two queues are used:
1. 'bulk' for a regular archival of all the resources
2. 'priority' for when a user edits one-off resource
This means that the 'bulk' queue can happily run slowly, chugging through the downloads, say once a week. And meanwhile, if a new resource is put into CKAN then it can be downloaded straight away on the 'priority' queue.
This means that the 'bulk' queue can happily run slowly, archiving large quantities slowly, such as re-archiving every single resource once a week. And meanwhile, if a new resource is put into CKAN then it can be downloaded straight away via the 'priority' queue.
Installation
------------
...
...
@@ -34,29 +62,162 @@ To install ckanext-archiver:
. /usr/lib/ckan/default/bin/activate
2. Install the ckanext-archiver Python package into your virtual environment::
2. Install the ckanext-archiver and ckanext-report Python packages into your virtual environment::
4. Add ``archiver`` to the ``ckan.plugins`` setting in your CKAN
4. Add ``archiver report`` to the ``ckan.plugins`` setting in your CKAN
config file (by default the config file is located at
``/etc/ckan/default/production.ini``).
5. Restart CKAN. For example if you've deployed CKAN with Apache on Ubuntu::
5. Install a Celery queue backend - see later section.
6. Restart CKAN. For example if you've deployed CKAN with Apache on Ubuntu::
sudo service apache2 reload
Upgrade from version 0.1 to 2.x
-------------------------------
NB If upgrading ckanext-archiver and use ckanext-qa too, then you will need to upgrade ckanext-qa to version 2.x at the same time.
NB Previously you needed both ckanext-archiver and ckanext-qa to see the broken link report. This functionality has now moved to ckanext-archiver. So now you only need ckanext-qa if you want the 5 stars of openness functionality.
1. Activate your CKAN virtual environment, for example::
. /usr/lib/ckan/default/bin/activate
2. Install ckanext-report (if not already installed)
Whilst this could possibly be a problem with the server, it is most likely due to you needing to install SNI support on the machine that ckanext-archiver runs. Server Name Indication (SNI) is for when a server has multiple SSL certificates, which is a relatively new feature in HTTPS. This requires installing a recent version of OpenSSL plus the python libraries to make use of this feature.
If you have SNI support installed then this should command run without the above error::
You should also check your OpenSSL version is greater than 1.0.0::
python -c "import ssl; print ssl.OPENSSL_VERSION"
Apparently SNI was added into OpenSSL version 0.9.8j but apparently there are reported problems with 0.9.8y, 0.9.8zc & 0.9.8zg so 1.0.0+ is recommended.
For more about enabling SNI in python requests see:
1. Enabling Archiver to listen to resource changes
If you want the archiver to run automatically when a new CKAN resource is added, or the url of a resource is changed,
then edit your CKAN config file (eg: development.ini) to enable the extension:
...
...
@@ -73,40 +234,64 @@ Config settings
The following config variable should also be set in your CKAN config:
* ckan.site_url: URL to your CKAN instance
* ``ckan.site_url`` = URL to your CKAN instance
This is the URL that the archive process (in Celery) will use to access the CKAN API to update it about the cached URLs. If your internal network names your CKAN server differently, then specify this internal name in config option: ckan.site_url_internally
This is the URL that the archive process (in Celery) will use to access the CKAN API to update it about the cached URLs. If your internal network names your CKAN server differently, then specify this internal name in config option: ``ckan.site_url_internally``
* ckan.cache_url_root: URL that will be prepended to the file path and saved against the CKAN resource,
providing a full URL to the archived file.
3. Additional Archiver settings
The following Archiver settings can be changed by creating a copy of ``ckanext/archiver/default_settings.py``
at ``ckanext/archiver/settings.py``, and editing the variables:
Add the settings to the CKAN config file:
* ``ckanext-archiver.archive_dir`` = path to the directory that archived files will be saved to (e.g. ``/www/resource_cache``)
* ``ckanext-archiver.cache_url_root`` = URL where you will be publicly serving the cached files stored locally at ckanext-archiver.archive_dir.
* ``ckanext-archiver.max_content_length`` = the maximum size (in bytes) of files to archive (default ``50000000`` =50MB)
* ``ckanext-archiver.user_agent_string`` = identifies the archiver to servers it archives from
4. Nightly report generation
* ARCHIVE_DIR: path to the directory that archived files will be saved to
* MAX_CONTENT_LENGTH: the maximum size (in bytes) of files to archive
Configure the reports to be generated each night using cron. e.g.::
Alternatively, if you are running CKAN with this patch:
5. Your web server should serve the files from the archive_dir.
With nginx you insert a new ``location`` after the ckan one. e.g. here we have configured ``ckanext-archiver.archive_dir`` to ``/www/resource_cache`` and serve these files at location ``/resource_cache`` (i.e. ``http://mysite.com/resource_cache`` )::
server {
# ckan
location / {
proxy_pass http://127.0.0.1:8080/;
...
}
# archived files
location /resource_cache {
root /www/resource_cache;
}
Legacy settings:
Older versions of ckanext-archiver put these settings in
ckanext/archiver/settings.py as variables ARCHIVE_DIR and MAX_CONTENT_LENGTH
but this is deprecated as of ckanext-archiver 2.0.
There used to be an option DATA_FORMATS for filtering the resources
archived, but that has now been removed in ckanext-archiver v2.0, since it
is now not only caching files, but is seen as a broken link checker, which
applies whatever the format.
Using Archiver
--------------
First, make sure that Celery is running for each queue
For test/local use, you can do this by going to the CKAN root directory and typing::
First, make sure that Celery is running for each queue. For test/local use, you can run::
paster celeryd --queue=priority -c <path to CKAN config>
paster --plugin=ckanext-archiver celeryd2 run all -c development.ini
and in a separate terminal::
However in production you'd run the priority and bulk queues separately, or else the priority queue will not have any priority over the bulk queue. This can be done by running these two commands in separate terminals::
paster celeryd --queue=bulk -c <path to CKAN config>
paster --plugin=ckanext-archiver celeryd2 run priority -c production.ini
paster --plugin=ckanext-archiver celeryd2 run bulk -c production.ini
For production use, we recommend setting up Celery to run with supervisord.
i.e. if you browse this path on your website: `/api/action/package_show?id=<package_name>` then you don't see the `archiver` key at the dataset level or resource level.
Check the `paster archiver update` command completed ok. Check that the `paster celeryd2 run` has done the archiving ok. Check the dataset has at least one resource. Check that you have ``archiver`` in your ckan.plugins and have restarted CKAN.
'SSL handshake' error
~~~~~~~~~~~~~~~~~~~~~
When archiving resources on servers which use HTTPS, you might encounter this error::
