[GNUnet-developers] configure option --disable-autostart added

[Sree Harsha Totakura]

Dear Developers,

I just added a new configure option --disable-autostart to disable auto
startup of services by ARM.  If this option is not given, auto startup
of services by ARM is enabled; this is the behavior before.

The rationale for this is that during large scale experiments we only
test some subsystems of GNUnet and hence we only need to enable those
respective services to be run for each peer.

The problem is not with the presence of these unnecessary services --
ARM handles them efficiently and only starts them when a request for
these service arrives instead of starting them all together.  For this,
ARM allocates the listening sockets for the services and whenever a
connection is made to these sockets it starts the services and passes
the listening sockets to them.

The problem happens with this behavior while starting a lot of peers on
systems with network file systems.  When the services are configured to
use UNIX domain sockets (which is mostly the case for all services on a
UNIX based system), ARM tries to first allocate the domain sockets on
the network file systems for these services.  As we start a lot of
peers, lot of ARM processes try to allocate these sockets.  As a result,
the network file system gets quickly saturated and the bind calls get
delayed, resulting in a delayed peer startup times.

This is to be addressed with the new --disable-autostart configure
option.  For this all services should use the line
 "AUTOSTART = @AUTOSTART@"
instead of
 "AUTOSTART = YES"
The option, if used, will then replace "@AUTOSTART@" with "NO" in the
default configurations of the services.

Should you as a service developer think your service should not be
started by default at all, you may set "AUTOSTART" to "NO" in the
default configuration.  Otherwise, I request you to always use
"AUTOSTART = @AUTOSTART@".

One may now suggest that instead of having this option, the experiments
can use a configuration which overrides each services' "AUTOSTART".  But
with a new service showing up every fortnight, it is cumbersome and
error prone to update experiment's configurations.

Regards,
Sree Harsha