Open mathog opened 4 years ago
Solved it.
The problem was that "firewalld" was running and its configuration was not in any way visible with "iptables --list". The RPMs built from the Fedora src.rpms did not set rules for firewalld which would let them work (accept connections). Without those rules gmond could still talk to gmond on other sysetms.
I only figured this out because there was for some reason a firewalld rule for "cockpit" so that nmap from another machine showed port 9090 even though lsof on the CentOS 8 machine had nothing on that port. cockpit was not running or installed, and never had been.
So add the appropriate ports to the firewalld configuration. (Forget about iptables, since it is broken/not available on CentOS 8. iptables --list still runs but it does not actually show the existing rules!)
Has anybody successfully built ganglia RPMs for CentOS 8? There was a version in EPEL for CentOS 7 but they do not have one for 8.
I used the method shown below and gmond appears to be collecting data (when run with -d 20 -f, it even lists the node name) but it won't share it. It lists requests as they happen, and returns a data structure. However, gstat shows 0 for all hosts fields and says there is no gexec. (Yes, gmond.conf was set to gexec = yes). telnet to the port shows "!ELEMENT HOSTS EMPTY" instead of hosts information. There is only the one node in this "cluster", perhaps that is the issue?
Built and tested like so:
More info. A laptop running Ubuntu 18.04 LTS is on the same network. Started ganglia on it with:
So apparently the 3.7.2 gmond can send but not receive information. There are no firewalls running and SELINUX makes no difference - gstat on 3.6.0 and 3.7.2 show the same information (more or less) when they query the same gmond server.