tree 8c4771f88b6d38c790bce76505a7d6d00d9b74f8
parent a23d9303644add41dccb24694410b26941a6e13e
author Kevin Lubick <kjlubick@google.com> 1571919196 -0400
committer Kevin Lubick <kjlubick@google.com> 1571925982 +0000

[gold] Introduce expectations.ReadOnly to use fewer copies.

This is a big change - now instead of clients getting an
unchanging copy of the expectations when they ask the Store
for it, they are getting a pointer to the current state of
expectations.

For example, if someone triages something, firestore sends
a notification (via the QuerySnapshots in fs_expstore), which
will modify the source of truth (fs_expstore.cache), which
in turn updates the version for all clients (in a thread-safe
way, if all the mutexes line up).

This should reduce latency in many cases, because the ~300ms
needed to copy all the expectations for Skia adds up. Additionally,
it should reduce the amount of RAM needed, by avoiding so
many of those copies.

GetCopy preserves the old functionality for the few clients
that needed to modify the expectations after fetching
(simple_baseliner)

Bug: skia:9557, skia:9080
Change-Id: Ie21c985cba9ffc37306b2ce1eafa46c6df334326
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/250236
Reviewed-by: Ben Wagner aka dogben <benjaminwagner@google.com>
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>