Hi all
Probably need some of the coder types to answer this one for me. For the different network tests, where does Xymon get the IP address from?
In particular, ping, ssh, oratns, dns etc. I think I read somewhere that for ping, Xymon does a host name lookup. But is this the case for the other tests?
Thanks Vernon
If you have "testip" in the server's stanza in bb-hosts then Hobbit uses the ip address in the bb-hosts file. Otherwise it does a DNS lookup based on the server's name.
Thanks, Larry Barber
On Mon, Jul 19, 2010 at 3:36 AM, Vernon Everett <everett.vernon at gmail.com>wrote:
Hi all
Probably need some of the coder types to answer this one for me. For the different network tests, where does Xymon get the IP address from?
In particular, ping, ssh, oratns, dns etc. I think I read somewhere that for ping, Xymon does a host name lookup. But is this the case for the other tests?
Thanks Vernon
Can somebody confirm this? We had a monitored host, configured incorrectly in bb-hosts. The IP address was incorrect. (The IP address was allocated to a router somewhere on the network) The entry was as follows. (Name & IP changed) 1.2.3.4 dbsrv1 # ssh oratns:1578 NOCOLUMNS:memory Should have been 2.3.4.5 dbsrv1 # ssh oratns:1578 NOCOLUMNS:memory
The conn test was green. It could have been pinging the real host (nslookup dbserv1 gave the correct IP) Or it could have used the 1.2.3.4 IP of the router, which responds to a ping.
However, the oratns and ssh columns were perpetually red. Obviously, the router has no database listener, nor was it accepting ssh connections (limited using ACLs) So it looked like it was using the bb-hosts IP. If it was doing a name lookup, it would have used the correct IP, and returned green. When I changed the IP in bb-hosts to the correct IP, oratns and ssh both went green.
I always thought that Xymon does a name lookup, but from this, it appears as if oratns and ssh use the IP address in bb-hosts. Which was it using for the ping? Lookup, or bb-hosts?
Cheers Vernon
On Mon, Jul 19, 2010 at 9:43 PM, Larry Barber <lebarber at gmail.com> wrote:
If you have "testip" in the server's stanza in bb-hosts then Hobbit uses the ip address in the bb-hosts file. Otherwise it does a DNS lookup based on the server's name.
Thanks, Larry Barber
On Mon, Jul 19, 2010 at 3:36 AM, Vernon Everett <everett.vernon at gmail.com>wrote:
Hi all
Probably need some of the coder types to answer this one for me. For the different network tests, where does Xymon get the IP address from?
In particular, ping, ssh, oratns, dns etc. I think I read somewhere that for ping, Xymon does a host name lookup. But is this the case for the other tests?
Thanks Vernon
Vernon Everett wrote:
Can somebody confirm this? We had a monitored host, configured incorrectly in bb-hosts. The IP address was incorrect. (The IP address was allocated to a router somewhere on the network) The entry was as follows. (Name & IP changed) 1.2.3.4 dbsrv1 # ssh oratns:1578 NOCOLUMNS:memory Should have been 2.3.4.5 dbsrv1 # ssh oratns:1578 NOCOLUMNS:memory
The conn test was green. It could have been pinging the real host (nslookup dbserv1 gave the correct IP) Or it could have used the 1.2.3.4 IP of the router, which responds to a ping.
However, the oratns and ssh columns were perpetually red. Obviously, the router has no database listener, nor was it accepting ssh connections (limited using ACLs) So it looked like it was using the bb-hosts IP. If it was doing a name lookup, it would have used the correct IP, and returned green. When I changed the IP in bb-hosts to the correct IP, oratns and ssh both went green.
I always thought that Xymon does a name lookup, but from this, it appears as if oratns and ssh use the IP address in bb-hosts. Which was it using for the ping? Lookup, or bb-hosts?
See 'man bbtest-net' - it depends on what options you have under [bbnet] against bbtest-net in hobbitlaunch.cfg
... Note: bbtest-net performs the connectivity test (ping) based on the hostname, unless the host is tagged with "testip" or the "--dns=ip" option is used. So the target of the connectivity test can be determined by your /etc/hosts file or DNS. ... --dns=[ip|only|standard] Determines how bbtest-net finds the IP adresses of the hosts to test. By default (the "standard"), bbtest-net does a DNS lookup of the hostname to determine the IP address, unless the host has the "testip" tag, or the DNS lookup fails. With "--dns=only" bbtest-net will ONLY do the DNS lookup; it it fails, then all services on that host will be reported as being down. With "--dns=ip" bbtest-net will never do a DNS lookup; it will use the IP adresse speci- fied in bb-hosts for the tests. Thus, this setting is equivalent to having the "testip" tag on all hosts. Note that http tests will ignore this setting and still perform a DNS lookup for the hostname given in the URL; see the "bbtest-net tags for HTTP tests" sec- tion in bb-hosts(5)
David.
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On Mon, 19 Jul 2010 16:36:12 +0800, Vernon Everett wrote:
Probably need some of the coder types to answer this one for me. For the different network tests, where does Xymon get the IP address from?
If the host has a "testip", Xymon uses the IP in bb-hosts.
Otherwise it tries a DNS lookup on the hostname, and uses the IP returned from that. If the DNS lookup fails, it will fall back to the IP listed in bb-hosts.
Henrik
Hi Henrik
Thanks for that. If I recall, about 2 or 3 years ago, it was you who told me that it first does a name lookup. Larry, sorry I didn't take you on your word. Although I was sure you were right, it contradicted what we were seeing here.
Tried another test, and set the server IP to 0.0.0.0 in bb-hosts, and it all went red again. :-(
It seems to resolve using nslookup on CLI, but not in bbtest.net Eventually added the --no-ares option, and all is good in our again.
This is the second time I have seen this issue. Any idea what causes it?
Cheers Vernon
On Tue, Jul 20, 2010 at 1:58 PM, Henrik Størner <henrik at hswn.dk> wrote:
On Mon, 19 Jul 2010 16:36:12 +0800, Vernon Everett wrote:
Probably need some of the coder types to answer this one for me. For the different network tests, where does Xymon get the IP address from?
If the host has a "testip", Xymon uses the IP in bb-hosts.
Otherwise it tries a DNS lookup on the hostname, and uses the IP returned from that. If the DNS lookup fails, it will fall back to the IP listed in bb-hosts.
Henrik
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In <AANLkTilWTJuol2MySad94PouqUt8ud65rGZqU1viZkaL at mail.gmail.com> Vernon Everett <everett.vernon at gmail.com> writes:
Tried another test, and set the server IP to 0.0.0.0 in bb-hosts, and it all went red again. :-(
It seems to resolve using nslookup on CLI, but not in bbtest.net Eventually added the --no-ares option, and all is good in our again.
Are you using a local DNS resolver, or a remote one ? Xymon tends to hit DNS servers pretty hard when starting all the network tests, so I strongly recommend using a local DNS cache.
It could be a bug in the C-ARES library, of course.
Henrik
Hi Henrik
Our DNS servers exist in Wintendo land. so I guess that's remote. I could set up a local DNS, but, because of the nature of this contract, and the way the support company works, I don't think I should. (We are setting up everything, and a remote services mob are going to be administering it all. Transition to remote services is supposed to happen in the next 2 months) It works with --no-ares, so I am not going to pursue it any further - unless I can assist in some way with debugging info. If there is benefit to be gained for the dev team, let me know you would like me to do.
Cheers Vernon
On Sun, Aug 1, 2010 at 11:50 PM, Henrik Størner <henrik at hswn.dk> wrote:
In <AANLkTilWTJuol2MySad94PouqUt8ud65rGZqU1viZkaL at mail.gmail.com> Vernon Everett <everett.vernon at gmail.com> writes:
Tried another test, and set the server IP to 0.0.0.0 in bb-hosts, and it all went red again. :-(
It seems to resolve using nslookup on CLI, but not in bbtest.net Eventually added the --no-ares option, and all is good in our again.
Are you using a local DNS resolver, or a remote one ? Xymon tends to hit DNS servers pretty hard when starting all the network tests, so I strongly recommend using a local DNS cache.
It could be a bug in the C-ARES library, of course.
Henrik
To unsubscribe from the xymon list, send an e-mail to xymon-unsubscribe at xymon.com
On Sun, August 1, 2010 18:37, Vernon Everett wrote:
Hi Henrik
Our DNS servers exist in Wintendo land. so I guess that's remote. I could set up a local DNS, but, because of the nature of this contract, and the way the support company works, I don't think I should. (We are setting up everything, and a remote services mob are going to be administering it all. Transition to remote services is supposed to happen in the next 2 months) It works with --no-ares, so I am not going to pursue it any further - unless I can assist in some way with debugging info. If there is benefit to be gained for the dev team, let me know you would like me to do.
Vernon,
You're the best judge of what's appropriate vis-a-vis your contract and support channels, but if there's any cordiality there, you might touch base with them on setting up a caching-only named on your Xymon server. You'd be greatly decreasing somewhat gratuitous hits on their servers, and they might welcome it. You probably know that it's a very simple setup.
regards, j.
I will have a chat. There is a very cordial relationship, but politics, as always, makes it.....interesting. I am not going to go into any further detail in an open forum. :-)
Before I have my chat though, I need to be armed with more info. Using little words, and sock-puppets (if required), can you explain exactly what the ares doo-hicky actually does? What happens differently when we run Xymon with and without the --no-ares?
Cheers Vernon
On Mon, Aug 2, 2010 at 7:44 AM, Xymon User in Richmond < hobbit at epperson.homelinux.net> wrote:
On Sun, August 1, 2010 18:37, Vernon Everett wrote:
Hi Henrik
Our DNS servers exist in Wintendo land. so I guess that's remote. I could set up a local DNS, but, because of the nature of this contract, and the way the support company works, I don't think I should. (We are setting up everything, and a remote services mob are going to be administering it all. Transition to remote services is supposed to happen in the next 2 months) It works with --no-ares, so I am not going to pursue it any further - unless I can assist in some way with debugging info. If there is benefit to be gained for the dev team, let me know you would like me to do.
Vernon,
You're the best judge of what's appropriate vis-a-vis your contract and support channels, but if there's any cordiality there, you might touch base with them on setting up a caching-only named on your Xymon server. You'd be greatly decreasing somewhat gratuitous hits on their servers, and they might welcome it. You probably know that it's a very simple setup.
regards, j.
To unsubscribe from the xymon list, send an e-mail to xymon-unsubscribe at xymon.com
On Sun, August 1, 2010 21:41, Vernon Everett wrote:
I will have a chat. There is a very cordial relationship, but politics, as always, makes it.....interesting. I am not going to go into any further detail in an open forum. :-)
Before I have my chat though, I need to be armed with more info. Using little words, and sock-puppets (if required), can you explain exactly what the ares doo-hicky actually does? What happens differently when we run Xymon with and without the --no-ares?
You may get better answers from folks familiar with the actual code, but my take is that with --no-ares Xymon uses the threaded, synchronous system resolver library, which would tend to choke down the rate of hits against whatever DNS servers are used (and slow down the loop through bb-hosts), compared to ares.
With a caching local DNS server, you'd be optimizing the use of the hits against the "real" DNS servers, not repeating a lookup until the TTL has run on the last real lookup of the hostname. This would tend to mitigate the hammering from using the ares resolver functions.
Again, that's my take. Wait and see if anyone says I'm horribly wrong before taking that into a meeting.
participants (5)
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david.baldwin＠ausport.gov.au
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everett.vernon＠gmail.com
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henrik＠hswn.dk
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hobbit＠epperson.homelinux.net
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lebarber＠gmail.com