tree 395401354b8ea67abd0ce20a769af9f584b74a55
parent f4c99e70dad320abf84fd25a32ad5fce2bf16f4a
author Ed Tanous <edtanous@google.com> 1648018431 -0700
committer Ed Tanous <ed@tanous.net> 1649184646 +0000

Implement Expand

Section 7.3 of the Redfish specification lays out a feature called
"expand" that allows users to expand portions of the Redfish tree
automatically on the server side.  This commit implements them to the
specification.

To accomplish this, a new class, MultiAsyncResp is created, that allows
RAII objects to handle lifetime properly.  When an expand query is
generated, a MultiAsyncResp object is instantiated, which allows "new"
requests to attach themselves to the multi object, and keep the request
alive until they all complete.  This also allows requests to be created,
while requests are in flight, which is required for queries above
depth=1.

Negatives:
Similar to the previous $only commit, this requires that all nodes
redfish nodes now capture App by reference.  This is common, but does
interfere with some of our other patterns, and attempts to improve the
syntactic sugar for this proved unworkable.

This commit only adds the above to service root and Computer systems, in
hopes that we find a better syntax before this merges.

Left to future patches in series:
Merging the error json structures in responses.

The Redfish spec isn't very clear on how errors propagate for expanded
queries, and in a conforming we shouldn't ever hit them, but
nonetheless, I suspect the behavior we have is sub-optimal (attaching an
error node to every place in the tree that had an issue) and we should
attempt to do better in the future.

Tested (on previous patch):

curl --insecure --user root:0penBmc https://localhost:18080/redfish/v1\?\$expand\=.\(\$levels\=255\)
Returns the full tree

Setting $levels=1 query returns only a depth of 1 tree being returned.

Unit tests passing

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I874aabfaa9df5dbf832a80ec62ae65369284791d