Allow to configure the number of BK client worker threads

[merlimat]

Motivation

In broker, we should be allowed to configure the number of threads to be be used for the BK worker pool.

[eolivelli]

There is no need for this change, apart from documentation.

Since 2.8 (backported to 2.7.2)

Any configuration entry that starts with bookkeeper_ is passed to the BK client

[merlimat]

We need to have this documented and visible though.

[eolivelli]

Sorry I amended my comment.
I wanted to say that we just have to document this property.

[merlimat]

I think that having that in broker.conf is the most appropriate form to advertise the configurability of such parameter.

[eolivelli]

I think that having that in broker.conf is the most appropriate form to advertise the configurability of such parameter.

Yes. We could add the line to broker.conf.
Nothing more

[merlimat]

Having the bookkeeper_ prefix is good for settings that we don't expect to have to change in broker (while retaining the ability to do so), but for settings that are exposed directly in broker, we should follow the existing convention and naming scheme.

For this setting, I believe that it is very relevant to the performance of brokers and we should have it in same consistent way as the other BK client settings within broker.conf.

[sijie]

Having this setting available can emphasize its importance. Because it is very relevant to the performance. +1 on adding this setting.

[sijie]

@eolivelli

bookkeeper_ prefix is designed for allowing configuring bookkeeper client settings if they are not available in the broker configuration. But if there are settings critical for configuring bookkeeper client, we should make new settings for them, make them explicit in the broker configuration and follow the naming convention of the other bookkeeper client settings.

[eolivelli]

Makes sense to me

+1