[Gluster-devel] gfapi: add function to set client-pid

[Ravishankar N]

Hello,

I'm planning to expose setting client-pid for gfapi clients via a new 
api, something like `glfs_set_client_pid (fs, pid)`.
The functionality already exists for fuse mounts via the 
--client-pid=$PID option, where the value is captured in 
glusterfs_ctx_t->cmd_args->client_pid.

Background:

If the glusterfs eventing framework is enabled, AFR sends child-up/child 
down events (via the gf_event() call) in the notify code path whenever 
there is a connect/disconnect at AFR level. While this is okay for 
normal client processes, it does not make much sense if the event is 
coming from say glfsheal, which is a gfapi based program (having the AFR 
xlator) that is invoked when you run the heal info set of commands. Many 
applications periodically run heal info to monitor the heals and display 
it on the dashboard (like tendryl), leading to a flood of child up/ down 
messages to the application monitoring these events.

We need to add a unique key=value to all such gf_event() calls in AFR, 
based on which the consumer of the events can decide to ignore them if 
needed. This key-value can be client-pid=$PID, where PID can be 
GF_CLIENT_PID_SELF_HEALD for selfheal daemon, GF_CLIENT_PID_GLFS_HEAL 
for glfsheal etc (these values are already defined in the code). This is 
why we need a way to set the client-pid for gfapi clients as well.

Another approach would be to add an xlator option (say 'client-name') 
specific to AFR  and use that as the key-value pair but it seems to be 
an overkill to do that just for the sake of eventing purposes. Besides, 
the pid approach can also be extended to other gluster processes like 
rebalance, shd and other daemons where AFR is loaded but AFR 
child-up/down events from it are not of any particular interest.These 
daemons will now have to be spawned by glusterd with the --client-pid 
option.

Regards,
Ravi