ckanext-files 0.2.4

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ckanext-files

Files as first-class citizens of CKAN. Upload, manage, remove files directly and attach them to datasets, resources, etc.

Requirements

Compatibility with core CKAN versions:

CKAN version	Compatible?
2.8	yes
2.9	yes
2.10	yes
master	yes

CKAN v2.8 and v2.9 are supported by ckanext-files v0.2. Starting from v1.0 this extension switches to CKAN support policy of two latest CKAN releases. I.e, ckanext-files v1.0 supports only CKAN v2.10 and v2.11.

v0.2 will not receive any new features, only bug-fixes.

It's recommended to install the extension via pip, so you probably have all the requirements pinned already. If you are using GitHub version of this extension, stick to the vX.Y.Z tags to avoid breaking changes. Check the changelog before upgrading the extension.

Installation

To install ckanext-files:

1. Install the extension

   # minimal installation
   pip install ckanext-files
   
   # Google Cloud Storage support
   pip install 'ckanext-files[gcs]'
   

2. Add files to the ckan.plugins setting in your CKAN config file.

3. Run DB migrations

   # CKAN >= v2.9
   ckan db upgrade -p files
   
   # CKAN == v2.8
   paster --plugin=ckanext-files files -c ckan.ini initdb
   

Usage

Configure the storage

Before uploading any file, you have to configure a named storage. Tell extension which driver to use(i.e, where and how data will be stored), add few storage specific settings and you are ready to go. Let's start from the Redis driver, because it has minimal requirements in terms of configuration.

Add the following line to the CKAN config file:

ckanext.files.storage.my_storage.type = files:redis

Look at this option. The prefix ckanext.files.storage. will be the same for every configuration option related to storage. Then comes my_storage. It's a name of your storage. It doesn't change the behavior of the storage, but determines how options are grouped together and helps you to use multiple storages simultaneously. For example the following configuration adds two different storages:first_storage with prefix set to first: and second_storage with prefix set to second::

ckanext.files.storage.first_storage.type = files:redis
ckanext.files.storage.second_storage.type = files:redis

ckanext.files.storage.first_storage.prefix = first:
ckanext.files.storage.second_storage.prefix = second:

Our storage is called my_storage and after the storage's name comes option's name type. And it's value files:redis. type option tells us which driver we are going to use for the storage. files:redis is the name of the driver.

The recommended format of the driver name is <EXTENSION_NAME>:<STORAGE_TYPE>. But this format is not enforced, so you can see any value there. If you accidentally make a typo in the driver's name, starting from v2.10 CKAN will show you an error message on startup with the list of available drivers:

Invalid configuration values provided:
ckanext.files.storage.my_storage.type: Value must be one of ['files:bq_google_cloud_storage', 'files:fs', 'files:public_fs', 'files:redis', 'files:google_cloud_storage']
Aborted!

Storage is configured, so we can actually upload the file. Let's use ckanapi for this task. Files are created via files_file_create API action and this time we have to pass 3 parameters into it:

• name: the name of uploaded file
• upload: content of the file
• storage: name of the storage that stores the file(we just configured my_storage)

The final command is here:

ckanapi action files_file_create \
    name=hello.txt \
    upload='hello world' \
    storage=my_storage

And that's what you see as result:

{
  "atime": null,
  "completed": true,
  "ctime": "2024-03-12T22:08:05.185914",
  "id": "7f9a7676-5177-40f0-b610-0b47918fdccc",
  "mtime": null,
  "name": "hello.txt",
  "storage": "my_storage",
  "storage_data": {
    "content_type": "text/plain",
    "filename": "2f51aeff-96a5-4d79-8973-7867527d7f2e",
    "hash": "5eb63bbbe01eeed093cb22bb8f5acdc3",
    "size": 11
  }
}

Now go to Redis CLI and check the content of the file. Note, you cannot get the content via CKAN API, because it's JSON-based and downloading files doesn't suit its principles.

By default, Redis driver puts the content under the key <PREFIX><FILENAME>. Pay attention to FILENAME. It's the value available as storage_data.filename in the API response(i.e, 2f51aeff-96a5-4d79-8973-7867527d7f2e in our case), not the name of the real file you just uploaded.

PREFIX can be configured, but we skipped this step and got the default value: ckanext:files:default:file_content:. So the final Redis key of our file is ckanext:files:default:file_content:2f51aeff-96a5-4d79-8973-7867527d7f2e

redis-cli

127.0.0.1:6379> GET ckanext:files:default:file_content:2f51aeff-96a5-4d79-8973-7867527d7f2e
"hello world"

And before we moved further, let's remove the file, using ID we got when it was created:

ckanapi action files_file_delete id=7f9a7676-5177-40f0-b610-0b47918fdccc

# ... response from api

redis-cli

127.0.0.1:6379> GET ckanext:files:default:file_content:2f51aeff-96a5-4d79-8973-7867527d7f2e
(nil)

Usage in code

If you are writing the code and you want to interact with the storage directly, without the API layer, you can do it via a number of public functions of the extension.

Let's configure filesystem storage first. This time we are going to use the storage name default. This is "default" storage name - if you haven't specified explicitely the name of the storage when working with it(calling API actions, for example), default storage is used. So it's better to create this storage instead of making fancy names.

Filesystem driver has a mandatory option path that controls path, where files are stored. If path does not exist, storage will raise an exception by default. But it can also create missing path if you enable create_path option. Here's our final version of settings:

ckanext.files.storage.default.type = files:fs
ckanext.files.storage.default.path = /tmp/example
ckanext.files.storage.default.create_path = true

Now we are going to connect to CKAN shell via ckan shell CLI command and create an instance of the storage:

from ckanext.files.shared import get_storage
storage = get_storage('default')

Because you have all configuration in place, the rest is fairly straightforward. We will upload the file, read it's content and remove it from the CKAN shell.

Uploading is the most challenging step. As CKAN is based on Flask, we have to upload files as Flask does. For it we are going to create an instance of werkzeug.datastructures.FileStorage and pass bytes stream to its constructor. After that, we can pass the object into storage's upload method and specify the name of the upload.

from werkzeug.datastructures import FileStorage
from io import BytesIO

upload = FileStorage(BytesIO(b'hello world'))
result = storage.upload('file.txt', upload, {})

print(result)

... {'filename': 'd65da0fd-299a-433c-850e-086fdc5ebb7e',
...  'content_type': None,
...  'size': 11,
...  'hash': '5eb63bbbe01eeed093cb22bb8f5acdc3'}

result contains minimal amount of information that is required by storage to manage the file. In case of FS storage, it includes filename. If you visit /tmp/example directory, that we specified as a path for our storage, you'll see there a file with the name matching filename from result. And its content matches the content of our upload, which is quite an expected outcome.

But let's go back to the shell and try reading file from the python's code. We'll pass result to the storage's stream method, which produces a readable buffer based on our result. This buffer has read method so we can work with the buffer just as we usually do with IO streams:

buffer = storage.stream(result)
content = buffer.read()
print(content)

... b'hello world'

And finally we need to remove the file

storage.remove(result)

Usage in browser

You can upload files using JavaScript CKAN modules. The extension extends CKAN's Sandbox object(available as this.sandbox inside the JS CKAN module), so we can use shortcut and upload file directly from the DevTools. Open any CKAN page, switch to JS console and create the sandbox instance. Inside it we have files object, which in turn contains upload method. This method accepts File object for upload(the same object you can get from the input[type=file]).

sandbox = ckan.sandbox()
await sandbox.files.upload(
  new File(["content"], "file.txt")
)

... {
...    "id": "d6fa3096-613a-4b16-a0eb-b7a6ec91d690",
...    "name": "file.txt",
...    "storage": "default",
...    "ctime": "2024-03-12T23:08:11.291971",
...    "mtime": null,
...    "atime": null,
...    "storage_data": {
...        "filename": "f484d116-cf6f-4238-80e5-905849873be0",
...        "content_type": "application/octet-stream",
...        "size": 7,
...        "hash": "9a0364b9e99bb480dd25e1f0284c8555"
...    },
...    "completed": true
... }

If you are still using FS storage configured in previous section, switch to /tmp/example folder and check it's content:

ls /tmp/example
... f484d116-cf6f-4238-80e5-905849873be0

cat f484d116-cf6f-4238-80e5-905849873be0
... content

And, as usually, let's remove file using the ID from the upload promise:

sandbox.client.call('POST', 'files_file_delete', {
  id: 'd6fa3096-613a-4b16-a0eb-b7a6ec91d690'
})

UI

This extension provides a basic UI as an example and it's recommended to build your own UI if you need it. But we can still use default functionality for testing. Open the /user/<YOUR USERNAME>/files page of CKAN application in the browser.

Choose the file

Click on play button(the one with triangle icon) and wait a bit. If nothing changes, check JS console, it can show some errors when storage is not properly configured.

When upload finished, reload the page to see uploaded file.

Configuration

There are two types of config options for ckanext-files:

• Global configuration affects the common behavior of the extension
• Storage configuration changes behavior of the specific storage and never affects anything outside of the storage

Depending on the type of the storage, available options for storage change. For example, files:fs storage type requires path option that controls filesystem path where uploads are stored. files:redis storage type accepts prefix option that defines Redis' key prefix of files stored in Redis. All storage specific options always have form ckanext.files.storage.<STORAGE>.<OPTION>:

ckanext.files.storage.memory.prefix = xxx:
# or
ckanext.files.storage.my_drive.path = /tmp/hello

Below is the list of non-storage specific options. Details of the specific storage type can be found in the dedicated section of the storage type.

# Default storage used for upload when no explicit storage specified
# (optional, default: default)
ckanext.files.default_storage = default

# Configuration of the named storage.
# (optional, default: )
ckanext.files.storage.<NAME>.<OPTION> =

Starting from CKAN v2.10 you can check all available options for the storage type via config declarations CLI. First, add the storage type to the config file:

ckanext.files.storage.xxx.type = files:redis

Now run the command that shows all available config option of the plugin.

ckan config declaration files -d

Because redis storage adapter is enabled, you'll see all the options regsitered by redis driver alongside with the global options:

## ckanext-files ###############################################################
## ...
## Storage adapter used by the storage
ckanext.files.storage.xxx.type = files:redis
## The maximum size of a single upload.
## Supports size suffixes: 42B, 2M, 24KiB, 1GB. `0` means no restrictions.
ckanext.files.storage.xxx.max_size = 0
## Descriptive name of the storage used for debugging.
ckanext.files.storage.xxx.name = xxx
## Static prefix of the Redis key generated for every upload.
ckanext.files.storage.xxx.prefix = ckanext:files:default:file_content:

Sometimes you will see a validation error if storage has required config options. Let's try using files:fs storage instead of the redis:

ckanext.files.storage.xxx.type = files:fs

Now attempt to run ckan config declaration files -d will show an error, because required path option is missing:

Invalid configuration values provided:
ckanext.files.storage.xxx.path: Missing value
Aborted!

Add the required option to satisfy the application

ckanext.files.storage.xxx.type = files:fs
ckanext.files.storage.xxx.path = /tmp

And run CLI command once again. This time you'll see the list of allowed options:

## ckanext-files ###############################################################
## ...
## Storage adapter used by the storage
ckanext.files.storage.xxx.type = files:fs
## The maximum size of a single upload.
## Supports size suffixes: 42B, 2M, 24KiB, 1GB. `0` means no restrictions.
ckanext.files.storage.xxx.max_size = 0
## Descriptive name of the storage used for debugging.
ckanext.files.storage.xxx.name = xxx
## Path to the folder where uploaded data will be stored.
ckanext.files.storage.xxx.path =
## Create storage folder if it does not exist.
ckanext.files.storage.xxx.create_path = false