For each DetailedView subclass, we add a `warnings` array to:
1. The top-level response.
2. Each individual call under the `details` key.
We use the `.thresholds` hash on the DetailedView to determine what's a
warning. If that hash is empty (the default), then the warnings array
will always be empty.
Peek attempts to serialize results with `to_json`, which calls
`ActiveSupport::JSON`. If an object is passed to `to_json` that contains
instance variables, `ActiveSupport` will attempt to recursively traverse
all variables.
The problem is that we can get into an infinite loop if the instance
references to an instance that references to something else that points
back to the same instance.
To avoid this mess, we just call `to_s` on the object. It appears only
`Gitlab::Git::Repository` and `::Repository` are the culprits here.
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/65404
This uses an ActiveRecord subscriber to get queries and calculate the
total query time from that. This means that the total will always be
consistent with the queries in the table. It does however mean that we
could potentially miss some queries that don't go through ActiveRecord.
Making this change also allows us to unify the response JSON a little
bit, making the frontend slightly simpler as a result.
This will help diagnose the source of excessive I/O from Rugged
calls. To implement this, we need to obtain the full list of arguments
sent to each request method.
