Code for the heros: Better reactive JMAP...

[chibenwa]

XUserAuthenticationStrategy is blocking

Executed on blocking call wrapper.

To handle this well:

• [x] Switch to AsyncCache in AbstractDomainList
• [x] Reactified version for DomainList::containsDomain
• [x] Reactified version for UsersRepository::assertValid
• [x] Reactify XUserAuthenticationStrategy that do not need to be switched off onto another threads

Current impact: blocking call wrapper in mobilised on each and every request because of this...

AliasReverseResolverImpl is blocking

The underlying RRT exposes iterables which are inherantly blocking.

recipientRewriteTable.listSources(...) actually is just a mere wrapper around a cassandra table and would be easy to reactify.

Then the overall algorithm could be reactified CF https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Flux.html#expand-java.util.function.Function-

This is called upon sending email (likely to be blocking anyway) but also listing identities which is not an uncommon request.

[chibenwa]

-> Those were identified doing wall clock profiling onto the JMAP pods

./profiler.sh -e wall -d 600 -t -i 1ms -I '*james*' -X '*JamesMailSpooler*' -X '*smtp*' -f /root/wall-jmap.html 1

[chibenwa]

See https://github.com/apache/james-project/pull/2228 for AliasReverseResolverImpl is blocking

[chibenwa]

See https://github.com/apache/james-project/pull/2235 for XUser