FR: enable --idle-threads by default

[renecannao]

We too often recommend to use --idle-threads (see doc), because it seems suitable for the majority of the workload.
We should consider enabling --idle-threads as default, and add a new command line argument to disable it, for example --no-idle-threads .

What workloads benefit from not using --idle-threads?
Extremely busy workloads, for example the ones executing during sysbench benchmark.
But the majority of real workloads have very different pattern than sysbench.

[Nrezinorn]

I would like this as our current workaround is to update the systemd unit file via puppet -> daemon reload -> restart proxysql.

Alternatives could be:
EnvironmentFile=/path/to/distro/configs (eg: /etc/sysconfig/proxysql on redhat-based distros )
and starting the unit with the exported $EXTRA_PARAMS if they are set. This would allow config management such as puppet/chef/etc to easily change setting flags without extra work.

Only downside is managing those configuration files per distro, but the flexibility it provides may outweigh.

[pondix]

The idea proposed by @Nrezinorn is an elegant solution, since we are using systemd going forward we should add an EnvironmentFile, this will be useful for cases such as this as well as others.

This will require considerable testing as we will need to verify it is used as expected across all distributions and will form part of the upcoming package build refactoring tasks planned.

For the time being I've modified both the unit file and init scripts to use --idle-threads by default.

v2.0.11 will run with auxiliary threads enabled by default!

[pondix]

Closing this, work will be continued on #2722