On Wed, Nov 24, 2021 at 5:55 AM Jacek Lewandowski
<lewandowski.ja...@gmail.com> wrote:
>
> I am just wondering how to represent in properties things like lists of
> non-scalar values?
>
In my experience properties are not sufficient for complex
configuration sorta for this reason, that's why using structured YAML
(or any structured configuration language) is so much more powerful
than a properties file. I think if we leaned into structured
configuration we'd have mostly maps of maps pointing to scalars which
are well addressed by dot encoding.
Dot encoding only works down to the first non scalar/object leaf node
and then the value needs to be structured. So a list of maps for
example would be in the value, for example in {"a": {"b": 4, "c":
[{"d": 3}, {"d": 2}]}} you'd be able to query for 'a.b' -> 4 or
'a.b.c' -> [{"d": 3}, {"d": 2}]. Single scalar values are valid JSON
so if we have to have a text -> text encoding I'd go for the key is
the dot encoded key and the value is the JSON encoded value, that's
maybe the easiest way to generically represent complex structured
configuration in a flat key->value mapping.
I think Elasticsearch's live reconfiguration API [1] which accepts dot
encoded JSON and merges with on disk YAML and Puppet's Hiera
configuration language [2] which allows you to index into YAMLs using
dot encoding are some great interfaces for us to study. The latter
even allows the user to query into lists by using a number as the key
(similar to jq[3] except without the square brackets) so you could ask
for 'a.b.c.0' and get back {"d": 3}.
-Joey
[1]
https://www.elastic.co/guide/en/elasticsearch/reference/current/cluster-update-settings.html
[2] https://puppet.com/docs/puppet/6/function.html#get
[3] https://stedolan.github.io/jq/manual/
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