On Thu, Sep 14, 2023 at 1:06 PM Steve Lawrence wrote:
> ...
>
> And with changes to the API, we could maybe even avoid #1 without
> ThreadLocals. For example, instead of using a LayerTransformerFactory to
> create new LayerTransformer instances, maybe we just directly create new
> instances of
All fair points. After becoming a bit more familiar with how layers
work, I have some additional thoughts.
Currently the way layers work is we create a single
LayerTransformerFactory during schema compilation, and each time
parse/unparse comes across this layer it calls factory.newInstance()
(Reviving this discussion thread - it went quiet last few weeks, and I
forgot to hit 'send' on this reply)
I would suggest that layer transformers, UDFs, and charset definitions are
not very much like NiFi processors.
They're generally embedded in DFDL "component" schemas that are used by
I'm thinking the layer framework needs to allocate the layer
transformer instance in a thread-local manner so that if it
constructs mutable state that will be thread local also
One downside to this is layer transformers that are thread-safe
unnecessarily incur some amount of overhead, both in
In the CRC32 layer, the "optimization" was really just laziness. The use
case we have only needs constant known explicit lengths, so we wanted to
hard wire that, and not bother to support nor test any other cases.
But, had that worked, I would bet we would have made the mistake and
pre-allocated
I don't remember why NoCacheEvluatable was used, but you're I suspect
you're right that it was done so implementations are less likely to mess
things up. Note that NoCacheEvaluatable is also used for
ImplicitLengthEv. I'm not sure why it's used there either. Maybe
LayerLengthEv just copied
Lola Kilo and I were debugging a layer for CRC32 and found that the
LayerLengthEv is a NoCacheEvaluatable, so even if the schema does
dfdlx:layerLength="1240" a constant, the the layerLengthEv.optConstant is
None, which is because it is a NoCacheEvaluatable, which insists
optConstant is false to
