perfSONAR User Q&A and Other Discussion

[Mark Feit <>]

Paul MEBALE-ASSAKO writes:

 

1. in case pscheduler-assist-server is not mandatory, how can we deactivate it?  

 

It isn’t.  Don’t put it in the configuration file and pSConfig will revert to its default behavior of asking the pScheduler server on the local system.  pSConfig is currently hard-wired for its default host to be localhost.  More on that below.

 

2. since gethostname() returns the system's hostname that is not directly resolvable using a DNS but by a stub resolver, is there a way of tuning it so that it might return the fqdn? Or is there a way of modifying it for gethostname() to look into /etc/hosts instead of directly requesting DNS servers (/etc/resolv.conf) ?

 

The system hostname is an arbitrary string stored in the kernel; gethostname() retrieves it.   Traditionally, that name has had a matching entry in /etc/hosts and, often, DNS.  Neither is required, but it’s been a good convention for systems to identify themselves.

 

Since we don’t configure the systems where perfSONAR is installed, there have to be fallbacks for weird configurations.  It isn’t safe for us to assume that that the hostname or localhost will resolve into something or that 127.0.0.1 or ::1 exists.  pScheduler will use the hostname if it resolves into an address using the system’s resolver library.  That may or may not include DNS depending on local configuration.  Failing that, it will return the IP of an interface on the system, preferring loopbacks and IPv6.  (What I said yesterday about IPs that reverse-resolve to hostname was incorrect, so disregard that.)

 

Now that pSConfig is written in the same language as most of pScheduler (Python), we’ll probably start looking at making some of the functions in pScheduler’s library dealing with this stuff available to the rest of the project.  That will make some of the behavior more-uniform.

 

--Mark