New and updated Prometheus metrics

[tillprochaska]

This PR adds a few new metrics and extends existing metrics based on feedback. I’d recommend taking a look at the individual commits when reviewing this PR.

Corresponding documentation changes are in #3845 because the release/4.0.0 branch doesn’t yet have the recently updated tech docs from develop.

Users

I’ve added new active and locale labels to the aleph_users metric. This allows querying for the number of active users (e.g. within last 24h, 7d, 30d, …) and the number of users that use a specific UI locale.

# Number of all users
aleph_users{active="all"}

# Number of all users using the (default) English localization
aleph_users{locale="en", active="all"}

# Number of monthly active users using the German localization
aleph_users{active="30d", locale="de"}

Collections

Previously, there was a single aleph_collections metric that allowed querying for the number of collections by category (e.g. "casefile", "leak", "gazette", …). I have renamed this metric to be consistent with two new metrics that expose the number of collections by country and language.

# Number of leaks
aleph_collection_categories{category="leak"}

# Number of datasets or investigations
aleph_collection_categories{type="dataset"}
aleph_collection_categories{type="investigation"}

# Number of datasets or investigations by country
aleph_collection_countries{type="dataset", country="fr"}
aleph_collection_countries{type="investigation", country="fr"}

# Number of datasets or investigations by language
aleph_collection_languages{type="dataset", language="fra"}
aleph_collection_languages{type="investigation", language="fra"}

Entities

I’ve added a new metric to track the number of entities per schema type. This re-uses collection statistics that are pre-computed and cached in Redis, i.e. we do not send any (potentially expensive) ES aggregation queries during metrics collection.

# Number of `Person` entities
aleph_entities{schema="Person"}

API HTTP requests

I have added a new label auth_method to the aleph_http_requests_total. This allows us to query for the number of API requests that used an API key vs. a UI session token.

# Number of requests to `/api/2/entities` using an API key
aleph_http_requests_total{api_endpoint="entities.index", auth_method="api_key"}

[tillprochaska]

@catileptic This is now ready for review, even though one test is still failing. As discussed, this test fails because of an update of the phonenumbers Python package. The new version of the package has validation changes, and as a result phone numbers used in that particular test are determined to be invalid which causes the test to fail.

I haven’t yet understood completely whether phonenumbers is actually right about thes test phone numbers and the numbers are indeed invalid or if this is a regression and they should be treated as valid. At first glance they look like a reasonable German mobile phone number, but phone number prefixes in Germany are weird.

I’ll keep the test as is until I’ve found a definitive answer, but that shouldn’t block a review of the actual changes proposed in this PR.

[catileptic]

This looks good to me. Really appreciate adding the tests! Let's get this merged.