commit 44c9eb492ad706149fdae2e7b67f210da50938a0
author Edwin Kempin <ekempin@google.com> Thu May 06 14:02:13 2021 +0000
committer Edwin Kempin <ekempin@google.com> Fri May 07 13:25:40 2021 +0000
tree 13e76cf3446521bef03e5a58feade831c1f4959c
parent c89c399d5cb4050e333291ece5bcd08e08952f32

Load accounts in parallel when resolving code owners

After reading code owner emails from an OWNERS file they are resolved to
accounts. Resolving an email to an account requires doing multiple
checks and lookups. Doing the lookups for all emails at once is more
efficient than iterating over the emails and doing the lookups once for
each email:

1. Lookup external IDs for emails:
   The external IDs are retrieved from the external ID cache. Each
   access to the external ID cache requires reading the SHA1 of the
   refs/meta/external-ids branch. If external IDs for multiple emails
   are needed it is more efficient to use the
   ExternalIds.byEmails(String...) method instead of the
   ExternalIds.byEmail(String) method as the
   ExternalIds.byEmails(String…) method reads the SHA1 of the
   refs/meta/external-ids branch only once (and not once per email).

2. Lookup accounts:
   Accounts are retrieved from the account cache. Using the
   AccountCache.get(Set<Account.Id>) method loads accounts in parallel
   and hence it is more efficient than calling
   AccountCache.get(Account.Id) once for each account.

Doing the lookups only once for all emails requires rewriting the
CodeOwnerResolver class, as now all checks and transformations need to
be performed on the collection of emails, rather than on a single email.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: Ie7dd6f54a0c24c2c4a9018d32ddb66b8f466d32a