ELPP-3621 Downstream service sample: emit one event in response to article

[giorgiosironi]

For #29

See README for how much is implemented in this PR and what will follow.

Sample log:

downstream-sample_1                | Receiving: {'eventId': '7d5de096-6338-11e8-83a9-0242ac1a000c', 'happenedAt': '2018-05-29T12:04:50+00:00', 'aggregate': {'service': 'article-store', 'name': 'article-version', 'identifier': '0065'}, 'type': 'article.version.post.started', 'data': {'article_version': 1}}
downstream-sample_1                | Publishing: {'runId': None, 'type': 'downstream.crossref.started', 'message': 'We are happy to receive this paper and have put it into a queue', 'eventId': '72d65f3a-6339-11e8-b721-0242ac1a000a', 'happenedAt': '2018-05-29T12:11:42+00:00'}
downstream-sample_1                | Receiving: {'eventId': '7d6ef94e-6338-11e8-83a9-0242ac1a000c', 'happenedAt': '2018-05-29T12:04:50+00:00', 'aggregate': {'service': 'article-store', 'name': 'article-version', 'identifier': '0065'}, 'type': 'article.version.post.completed', 'data': {'article_version': 1}}
downstream-sample_1                | Publishing: {'runId': None, 'type': 'downstream.crossref.started', 'message': 'We are happy to receive this paper and have put it into a queue', 'eventId': '72d8925a-6339-11e8-b721-0242ac1a000a', 'happenedAt': '2018-05-29T12:11:42+00:00'}

[seanwiseman]

Seem __pycache__ directory is being commited

[giorgiosironi]

I'll be going on implementing feedback on Wednesday, assuming the general framework of #28 is confirmed.

[giorgiosironi]

Integrated with article store from master (only issue the missing runId), will also check the dashboard after it has changed to the new format.

[giorgiosironi]

Merged master, but the article store doesn't start (no logs are written) as requests to the container's 8000 port are refused despite the python manage.py runserver process being running.

[giorgiosironi]

It starts when running with docker-compose up article-store, but docker-compose up -V reproduces the problem for me.

[giorgiosironi]

Non-deterministic problem.

[giorgiosironi]

Some manual tinkering lead to:

Run 4df2280c-67f8-11e8-9208-0242ac1a0010
    event.article.version.post.started
    Jun 4, 2018, 1:07:59 PM
    event.downstream.crossref.started
    We are happy to receive this paper and have put it into a queue
    Jun 4, 2018, 1:07:59 PM
    event.article.version.post.completed
    Jun 4, 2018, 1:07:59 PM
    event.downstream.crossref.started
    We are happy to receive this paper and have put it into a queue
    Jun 4, 2018, 1:07:59 PM

[giorgiosironi]

Had to manually bind the queue to the second exchange however: https://github.com/php-amqplib/RabbitMqBundle/issues/367

[giorgiosironi]

Thought about adding depends_on: - downstream-sample for the dashboard-events, but it doesn't have that for the articles exchange and it's just a startup order (or build time) dependency, so wouldn't add any value.

[thewilkybarkid]

Can see it working, but seems to respond to any article event? I see two downstream.crossref.started events: one after article.version.post.started and one after article.version.post.completed. Would only expect to see the latter.

[seanwiseman]

Successfully receiving the downstream events locally.

Are we going to have some sort of filtering on the received events here? e.g. only act on type article.version.*.completed or something along those lines? I know its not strictly important for demo purposes but with its current implementation, once you add in the work flow steps it will be firing off downstream.crossref.started about 10+ times when realistically you would only want to trigger downstream once the initial article 'processing' has completed.

[giorgiosironi]

I'll put a filter on article.version.post.completed that seems the correct integration point.

[giorgiosironi]

Took a bit to understand the flow of routing keys but :+1: feel free to merge when conveniente.