perfSONAR User Q&A and Other Discussion

[Paul MEBALE-ASSAKO <>]

Hello Mark, 

Thank you for this explanation. 

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

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) ?

mebale-assako@lille-snd-021:~$ hostname

lille-snd-021

mebale-assako@lille-snd-021:~$ host $(hostname)

lille-snd-021.perfsonar.noc.renater.fr has address 193.55.202.16

mebale-assako@lille-snd-021:~$ dig $(hostname)

; <<>> DiG 9.18.30-0ubuntu0.22.04.2-Ubuntu <<>> lille-snd-021

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 42955

;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:

; EDNS: version: 0, flags:; udp: 4096

;; QUESTION SECTION:

;lille-snd-021.                 IN      A

;; AUTHORITY SECTION:

.                       1994    IN      SOA     a.root-servers.net. nstld.verisign-grs.com. 2025032500 1800 900 604800 86400

;; Query time: 4 msec

;; SERVER: 194.57.7.80#53(194.57.7.80) (UDP)

;; WHEN: Tue Mar 25 09:59:24 UTC 2025

;; MSG SIZE  rcvd: 117

Best regards

Paul Mebale

---

De: "Mark Feit" <>
À: "Paul MEBALE-ASSAKO" <>, "perfsonar-user" <>
Envoyé: Lundi 24 Mars 2025 23:44:21
Objet: Re: few questions about pscheduler-assist-server & pscheduler/hostname

Paul MEBALE-ASSAKO writes:

·         what's the point of questioning pscheduler-assist-server ?

In nearly all cases, where a pScheduler server is running on the same system as pSConfig, there’s no need for it.  The concept of an assist server is for instances when there isn’t one, which can be the case on systems that only have the pScheduler CLI installed and need a way to figure out if, say, say, a test called “throughput” exists and whether or not a proposed throughput test is valid.

 

mebale-assako@lille-snd-021:~$ sudo -u perfsonar  PSCHEDULER_LOCALHOST=toto python3 /usr/lib/perfsonar/psconfig/bin/psconfig_pscheduler_agent --config=/etc/perfsonar/psconfig/pscheduler-agent.json --verbose

....

2025-03-24 15:30:49,249 DEBUG pid=1117626 prog=base_agent.py func=run line=137 guid=830f947f-458b-467e-b5c6-64cfc9f9cc09 agent_conf_file=/etc/perfsonar/psconfig/pscheduler-agent.json msg=No pscheduler-assist-server specified. Defaulting to localhost

 

The current version of pSConfig doesn’t recognize the PSCHEDULER_* environment variables, largely because it was a port of the old version’s Perl code directly to Python.   It was recently decided to start using a couple of things from pScheduler’s library and, now that we have that dependency, it would probably make sense to start using all of it instead of separate code.

 

·         pscheduler/hostname returns a hostname. Does this name need to be resolved in a DNS server? where can we modify the entry to apply a different hostname?

The hostname endpoint returns the first of:

• The system’s hostname as reported by gethostname() if it can be resolved into an IP address.  This doesn’t  have to be resolvable using DNS, but we do recommend it.
• The hostname of the first interface whose IP address(es) can be reverse-resolved into a hostname.

The only place it’s used is by the monitor command, where the result is used as part of the display.  It doesn’t figure into URLs returned by the API; if an endpoint is accessed as https://ps.example.edu/pscheduler/..., any returned URL will look the same regardless of the hostname.

Hope that answers your questions.

--Mark