Move blocking readPair call to boundedElastic thread

[Arooba-git]

Hi! 🙂

We noticed you did a great job in ensuring the reactive modules indeed stay reactive end to end. The mailbox module, however, was discovered to still have a blocking call in CassandraMessageMapper class as detected by BlockHound:

This PR fixes this code. We also re-ran the tests and verified the performance (in terms of heap usage) before and after the fix:

Before

After

[quantranhong1999]

Thanks for your contribution <3

[chibenwa]

Can we manage to subscribe here only if read repairs are enabled ie probability > 0 ?

[Arooba-git]

Sure, you mean something like:

.doOnNext(counters -> {
       if (probability > 0) {
              Mono.fromRunnable(() -> {
                   readRepair(mailbox, counters);
              })
             .subscribeOn(Schedulers.boundedElastic())
             .subscribe();
       }
});

[chibenwa]

Yes

[Arooba-git]

@chibenwa I'm sorry could you guide how to access probability property here? 🤔

[chibenwa]

from the configuration

[chibenwa]

I'm oretty sure it should be

Suggested change

	if (this.cassandraConfiguration.getMailboxReadRepair() > 0) {
	if (this.cassandraConfiguration.getMailboxCountersReadRepair() > 0) {

[Arooba-git]

Oh, you mean we should update the name in the original configuration file too? 🤔

[Arsnael]

I believe what chibenwa is saying is:

• getMailboxReadRepair() is used in CassandraMailboxMapper
• for CassandraMessageMapper , we use getMailboxCountersReadRepairChanceMax() and/or getMailboxCountersReadRepairChanceOneHundred()

=> for example: https://github.com/apache/james-project/blob/master/mailbox/cassandra/src/main/java/org/apache/james/mailbox/cassandra/mail/CassandraMessageMapper.java#L197

[Arsnael]

Maybe we could extract that line actually in a function to avoid duplication, that we could call from there and from your code change :)

[chibenwa]

Also read repair could be a good place for pseudo random usage aka non blocking...

There is no need for cryptographioc grade randomness for such an application.

Maybe otherall this could be a better fix. WDYT?

[chibenwa]

Please provide a pseudo random implementation for read repairs