commit ce4e7c6609a6aaa51745350e2a6b0661793861b3
author Gal Paikin <paiking@google.com> Fri Aug 28 18:47:32 2020 +0300
committer Gal Paikin <paiking@google.com> Wed Sep 09 13:57:16 2020 +0300
tree 33d43d7bf2f4a9de191cb49c7718df9e3986e1bc
parent d85657b06d5e47a75c0fc943454606f9f86a762a

Migrate all emails to send async via asyncPostUpdate

Currently, postUpdate doesn't run async, and when we want to
send emails asynchronously, we need to do that manually (e.g
AddReviewersEmail).

The goal is to make the code more clean in regard to sending
emails, and also improve the performance of emails (since
not all of the emails were sent async until now, only most
of them). More async emails means we can return a response
before actually sending the email.

All other updates are not affected, and they are still
invoked synchronously.

Some tests were fixed, since some tests assumed emails are sent
synchronously.

Generally, the most significant fix for the tests is the one
in FakeEmailSender#waitForEmails and methods that call it. We
now wait for asyncPostUpdates to finish before we read any emails.

As a follow-up it's possible to do some more cleanup. E.g,
FakeEmailSender#nextMessage() is not great when emails are sent
concurrently and maybe it's better not to use it.
The reason it's not good is the fact that when two emails are sent
roughly at the same time and async, the order of arrival for those
emails is not deterministic.
However, this reason is not currently relevant since the config
sendemails.threadPoolSize defaults to 1 (so 2 emails can't race)
in our tests.

AbstractNotificationTest could also use some additional cleanup.
So far, #sent in that class was changed to support concurrent
sending emails (it doesn't use FakeEmailSender#nextMessage()).

@SendEmailExecutor is still needed due to Id8177b374. This is now
renamed to AsyncPostUpdateExecutor and is used for all async
updates.

Also, introduced asyncPostUpdates.threadPoolSize to override the
old sendemail.threadPoolSize. The latter is marked as deprecated.

We already sent some emails async, those were removed to not make
a thread call another thread.

Change-Id: I64a829176506ad3f36d708d63572705abf139b87