For historical reasons, the handling of element types for maps is inconsistent with other collection types.
Here we begin a multi-step process to make it consistent, starting by supporting both the "consistent" form of using a schema.Schema and an existing erroneous form of using a schema.Type directly. In subsequent commits we will phase out the erroneous form and require the schema.Schema approach, the same as we do for TypeList and TypeSet.
Accessing an interpolated value in a map through ConfigFieldReader can
fail, because GetRaw can't access interpolated values, so check if the
value exists at all by looking in the config. If the config has a value,
assume our map's value is interpolated and proceed as such.
We also need to lookup the correct schema to properly read a field from
a nested structure.
- Maps previously always defaulted to TypeString. Now check if Elem is a
ValueType and use that if applicable
- Lists now return the schema for nested element types, defaulting to a
TypeString like maps.
This only allows maps and lists to be nested one level deep, and the
inner map or list must only contain string values.
This adds a test and the support necessary to read from native maps
passed as variables via interpolation - for example:
```
resource ...... {
mapValue = "${var.map}"
}
```
We also add support for interpolating maps from the flat-mapped resource
config, which is necessary to support assignment of computed maps, which
is now valid.
Unfortunately there is no good way to distinguish between a list and a
map in the flatmap. In lieu of changing that representation (which is
risky), we assume that if all the keys are numeric, this is intended to
be a list, and if not it is intended to be a map. This does preclude
maps which have purely numeric keys, which should be noted as a
backwards compatibility concern.
Changing the Set internals makes a lot of sense as it saves doing
conversions in multiple places and gives a central place to alter
the key when a item is computed.
This will have no side effects other then that the ordering is now
based on strings instead on integers, so the order will be different.
This will however have no effect on existing configs as these will
use the individual codes/keys and not the ordering to determine if
there is a diff or not.
Lastly (but I think also most importantly) there is a fix in this PR
that makes diffing sets extremely more performand. Before a full diff
required reading the complete Set for every single parameter/attribute
you wanted to diff, while now it only gets that specific parameter.
We have a use case where we have a Set that has 18 parameters and the
set consist of about 600 items (don't ask 😉). So when doing a diff
it would take 100% CPU of all cores and stay that way for almost an
hour before being able to complete the diff.
Debugging this we learned that for retrieving every single parameter
it made over 52.000 calls to `func (c *ResourceConfig) get(..)`. In
this function a slice is created and used only for the duration of the
call, so the time needed to create all needed slices and on the other
hand the time the garbage collector needed to clean them up again caused
the system to cripple itself. Next to that there are also some expensive
reflect calls in this function which also claimed a fair amount of CPU
time.
After this fix the number of calls needed to get a single parameter
dropped from 52.000+ to only 2! 😃
A common issue with new resource implementations is not considering parts
of a complex structure that's used inside a set, which causes quirky
behavior.
The schema helper has enough information to provide a default reasonable
implementation of a set function that includes all non-computed attributes
in a deterministic way. Here we implement such a function and use it
when no explicit hashing function is provided.
In order to achieve this we encapsulate the construction of the zero
value for a schema in a new method schema.ZeroValue, which allows us to
put the fallback logic to the new default function in a single spot.
It is no longer valid to use &Set{F: schema.Set} and all uses of that
construct should be replaced with schema.ZeroValue().(*Set) .
We were waiting until the higher-level (m schemaMap) diffString method
to apply defaults, which was messing with set hashcode evaluation for
cases when a field with a default is included in the hash function.
fixes#824
James McGill