LeoFS Gateway - graceful configuration reload

[pannon]

Is there a way to gracefully reload gateway configuration without restarting the process itself?

We are modifying the http_custom_header.conf file quite often, would like to avoid gateway restarts if possible to reload the new headers.

[yosukehara]

@pannon

I've checked the current implementation, which only once load http_custom_header.conf at launching a LeoGateway node:

• leo_gateway_http_commons:start/1

How often does you reload the configuration? After receiving your answer, we will consider whether we need to implement reloading the configuration feature or not.

[pannon]

At this stage we are reloading every couple of days. In the testing environments multiple times a day.

[mocchira]

@pannon
Thank you for replying.
While still not decided to do what you've requested yet, we are considering your request positively :)

@yosukehara
Just in case,
If we go forward this issue, there are a few ways to realize.

• Add a reload command to leo_gateway script
  It can be realized through nodetool

### reload .conf files without restarting
$ ./package/leo_gateway/bin/leo_gateway reload

• Handle a specific OS signal (typically SIGHUP/SIGUSR1)
  It will be able to realize through Signal Service: RFC: Signal Service for OS Signals erlang/otp#1315

### reload .conf files without restarting
$ kill -HUP ${leo_gateway_pid} 

[pannon]

Thanks! Maybe something along the lines of nginx -t && nginx -s reload.
Would be nice to have a way for quick config syntax test before reloading, especially when things are plugged into automation frameworks like consul-template, Puppet, Salt, Chef, etc.

This would be a safe choice for most use cases and users.

[mocchira]

@pannon Thanks for your suggestion.
Conf test makes sense to me.
As it can be separated as another issue, I filed on #692.

[mocchira]

WIP.

Note: Since signal handling in Erlang has been supported from OTP20, we go for the nodetool way.

[mocchira]

@pannon It's been a long time since you filed this issue. We've finally implemented this feature and it will be shipped with upcoming 1.4.1 (probably today) so please give it a try once it gets released.

# reload
$ ./package/leo_gateway/bin/leo_gateway reload_http_conf
# conf test
$ ./package/leo_gateway/bin/leo_gateway test_http_conf

Feel free to reopen if you find any problems.