Fix ES index upgrades when using index aliases

[tillprochaska]

ES supports fetching the index config for multiple indices in a single request. We don’t make use of this, but for this reason the ES responses are an object with a key for each requested index. For example:

{
  "aleph-entity-company-v1": {
    "settings": { ... },
    "mappings: { ... }
  }
}

In case an index is requested using an alias, the key will be the original index name and not the alias, i.e. we cannot rely on the key being the name that was used to request the index, as this would fail in case aliases are used.

However, as we’re always requesting only a single index at a time, the response should always contain data for one index, so we can extract that without relying on the name of the index.

You can test the following scenarios:

• Creating an index from scratch:
  1. Delete one of the indexes: curl -X "DELETE" "http://localhost:9200/aleph-entity-company-v1"
  2. Run aleph upgrade.
  3. The logs should indicate that the index was created.
• Update an aliased index with incompatible mappings:
  1. Follow instructions in JIRA to reproduce the issue.
  2. Run aleph upgrade.
  3. This shouldn’t error and the logs should indicate that the configuration has been updated.

[stchris]

out of curiosity: how do you feel about merging these checks into a if len != 1?

[tillprochaska]

Fair point, I’ve changed this.

[stchris]

Looks and works great, thanks for the fix!