subscription-service

Microservice turns delta-notifications into emails.

Adding to docker-compose

First, add the service to your app's docker-compose.yml

  subscription:
    image: robbe7730/subscription-service:latest
    restart: unless-stopped
    environment:
      EMAIL_SUBJECT: "My subject"
      EMAIL_FROM: "[email protected]"
      BASE_URL: "http://example.com"
      MU_SPARQL_ENDPOINT: "http://database:8890/sparql"
    volumes:
      - ./config/subscription/:/config
    links:
      - database:database
      - deliver-email-service:deliver-email-service

Then, set up the configuration files:

Configuration

Environment variables

• EMAIL_SUBJECT: The subject of the email that will be sent.
• EMAIL_FROM: The address the email will be sent from.
• BASE_URL: The base URL of the application, used for determining graph URLs.
• MU_SPARQL_ENDPOINT: The endpoint the SPARQL queries should be sent to.
• USERFILES_DIR: The directory the userfiles (information the user still needs to be updated about) will be saved to
• LOGLEVEL: Defines the log level. See https://docs.python.org/3/howto/logging.html
• DEBUG_LOG_MAIL_DIR: If set, save sent mails to this folder as HTML

Templates

The config/subscription/templates folder will contain the Jinja template needed to render the email. This template will get three graphs as arguments:

• inserts contains all the triples that were added by this delta.
• deletes contains all the triples that were deleted by this delta.
• unchanged contains all the triples that were not modified by this delta.

Besides that, it also receives some URLs and namespaces for convenience.

In this template, the graphs can be queried by using Pythons slicing syntax to represent triples. If we want to render every owl:sameAs link that was removed from a given zitting, we can do the following:

{% for link in deleted[zitting:OWL.sameAs:] %}
  <a href="{{link}}">link</a>
{% endfor %}

Query files

To get the right data, the service also needs three SPARQL queries under config/subscription.

get_relevant_content.sparql

This query checks if there is relevant content for a given subject-URL. For example, if the subject-URL is a besluit:Zitting, the content may be every besluit:Agendapunt it handles.

The query should contain one variable ?content (with zero or more bindings), the URL of some relevant content. In the query file, the string SUBJECT_URL will be replaced with the actual URL at runtime.

construct_content.sparql

This query fetches all the relevant triples for a given content URL. The query should return a CONSTRUCTed graph with all data relevant to the content. In the query file, the string CONTENT_URL will be replaced with the actual URL of the content.

get_template_subjects.sparql

To make templating easier, we want some URLs available in the template file. We do this by querying the content for the URLs we want to use.

This query can return any number of variables, the name of the variable can be used in the template to represent the URL it was bound to in the query.

Note: If multiple bindings exist, only the first one will be used.

Database

Subscriptions are stored in the {BASE_URL}/graphs/subscriptions graph. Users are stored as follows:

<USER> a schema:Person;
       schema:email "EMAIL";
       ext:hasSubscription <FILTER>. # Can be multiple filters

An example of such a filter is:

<FILTER> a sh:NodeShape;
         sh:targetClass besluit:Agendapunt;
         sh:or (
           <FILTER-or1>
           <FILTER-or2>
         ).

<FILTER-or1> sh:and (
               <FILTER-or1-and1>
               <FILTER-or1-and2>
             ).

<FILTER-or1-and1> sh:pattern "werken";
                  sh:path terms:title.

<FILTER-or1-and2> sh:pattern "schoolstraat";
                  sh:path terms:title.

<FILTER-or2> sh:path terms:title;
             sh:pattern "politie".