Article Number: 38 Rating: Unrated Last Updated: Thu, Apr 28, 2016 at 9:49 PM
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1 Nagios Log Server - Logs Not Searchable or Not Coming In Article Number: 38 Rating: Unrated Last Updated: Thu, Apr 28, 2016 at 9:49 PM O ve r vie w When running a query in a dashboard, logs are not showing up when they should be. This guide will go through the steps to diagnose what is causing the issue. This article will use a scenario of a remote server sending syslogs to help provide a clear troubleshooting path. Log Server Name: nls 0 1 IP: Listening Port: TC P 5544 OS: CentOS 6.7 x64 Remote Server Sending Logs Name: c e nto s 14 IP: Sending Port: TC P 5544 OS: CentOS 6.7 x64 Re mo t e S e r ve r - C he c k Rs ys lo g C o nf ig This server has already been setup to send logs to nls 0 1 using the setup steps in the Log Server GUI. To confirm this has been done, the following file has been created and contains the following: /etc/rsyslog.d/99-nagioslogserver.conf ### Begin forwarding rule for Nagios Log Server NAGIOSLOGSERVER $WorkDirectory /var/lib/rsyslog # Where spool files will live NAGIOSLOGSERVER $ActionQueueFileName nlsfwdrule0 # Unique name prefix for spool files NAGIOSLOGSERVER $ActionQueueMaxDiskSpace 1g # 1GB space limit (use as much as possible) NAGIOSLOGSERVER $ActionQueueSaveOnShutdown on # Save messages to disk on shutdown NAGIOSLOGSERVER $ActionQueueType LinkedList # Use asynchronous processing NAGIOSLOGSERVER $ActionResumeRetryCount -1 # Infinite retries if host is down NAGIOSLOGSERVER # Remote host is: name/ip:port, e.g :514, port optional NAGIOSLOGSERVER # NAGIOSLOGSERVER ### End of Nagios Log Server forwarding rule NAGIOSLOGSERVER It s important to note here the following line: # NAGIOSLOGSERVER It s assumed that the server c e nto s 14 can resolve the address nls 0 1, 1 otherwise it won t be able to send it logs. To confirm this, execute the following command on c e nto s 14: ping nls01 -c 1 Output similar to this is expected if it can successfully resolve nls01: PING nls01.box293.local ( ) 56(84) bytes of data. 64 bytes from nls01.box293.local ( ): icmp_seq=1 ttl=64 time=0.273 ms --- nls01.box293.local ping statistics packets transmitted, 1 received, 0% packet loss, time 2ms rtt min/avg/max/mdev = 0.273/0.273/0.273/0.000 ms Output similar to this is expected if it C ANNOT T successfully resolve nls01: ping: unknown host nls01 Going back to that config line: # NAGIOSLOGSERVER indicates that the port type is TCP and the port number is IF it was UDP there would only be Re mo t e S e r ve r - C he c k Rs ys lo g I s Running Assuming the config is correct, you may want to make sure that rsyslogd is running: service rsyslog status
2 Output similar to this is expected if it is running: rsyslogd (pid 2098) is running... Output similar to this is expected if it is NO T running: rsyslogd is stopped If it is not running, you should start it: service rsyslog start Re mo t e S e r ve r - C he c k Fir e wa ll Rule s You want to make sure that the iptables firewall allows outbound traffic. By default there is no restrictions on outbound traffic, to confirm this execute the following command: iptables --list Output similar to this is expected: Chain INPUT (policy ACCEPT) ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT icmp -- anywhere anywhere ACCEPT all -- anywhere anywhere ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh Chain FORWARD (policy ACCEPT) Chain OUTPUT (policy ACCEPT) Specifically this last output is what we need to look at: Chain OUTPUT (policy ACCEPT) The first line has (AC C EP T) which means there is no restriction at the top level (it would say DROP if there was). The second line is simply headings for all the outbound rules that have been defined. Because there is no third line, there are NO outbound rules defined so the default here is to ACC outbound traffic (allow it). IF you had a restricted environment where outbound rules were DROP, you would need to add an outbound firewall rule for TCP port 5544 to nls01 on : /sbin/iptables -I OUTPUT -p tcp --destination-port d j ACCEPT service iptables save Re mo t e S e r ve r - Wa t c h O ut bo und Tr a f f ic To confirm that the log traffic is leaving the remote server we can run a tcpdump to watch the traffic. First we must install tcpdump: yum -y install tcpdump Wait while tcpdump is installed. Now execute the following command to watch the traffic: tcpdump src host and tcp dst port 5544 and dst host You ll receive this message first: tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size bytes An example of traffic flowing is as follows: 16:43: IP centos14.box293.local > nls01.box293.local.5544: Flags [P.], seq : , ack , win 115, options [nop,nop,ts val ecr ], length 55
3 If you don t see any traffic, it may just be that nothing is being logged and hence there is nothing to send. You can easily add a test entry to rsyslog which will generate traffic: Open an additional ssh session to the remote server (centos14) Execute the following command: logger TroubleshootingTest In your other SSH session you should now see a line of traffic which confirms that rsyslog is sending the logs onto nls01. Press C trl C to stop the tcpdump. Lo g S e r ve r - Wa t c h I nbo und Tr a f f ic To confirm that the log traffic is entering log server we can run a tcpdump to watch the traffic. This is similar to the previous steps except it confirms that the traffic has made it throug routers or firewalls between the remote server and the log server. First we must install tcpdump: yum -y install tcpdump Wait while tcpdump is installed. Now execute the following command to watch the traffic: tcpdump src host and tcp dst port 5544 and dst host You ll receive this message first: tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size bytes An example of traffic flowing is as follows: 16:52: IP centos14.box293.local > nls01.box293.local.5544: Flags [P.], seq : , ack , win 115, options [nop,nop,ts val ecr ], length 55 If you don t see any traffic, it may just be that nothing is being logged and hence there is nothing to send. You can easily add a test entry to rsyslog which will generate traffic: Open an additional ssh session to the remote server (centos14) Execute the following command: logger TroubleshootingTest In your log server SSH session you should now see a line of traffic which confirms that the traffic is hitting the log server. Press C trl C to stop the tcpdump. IF you don t see any traffic, then there may be a firewall or router blocking the traffic. Lo g S e r ve r - C he c k Fir e wa ll Rule s You want to make sure that the iptables firewall allows inbound traffic. By default there are restrictions on inbound traffic however Nagios Log Server creates the firewall rules to allow traffic. To view the rules execute the following command: iptables --list Output similar to this is expected: Chain INPUT (policy ACCEPT) ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT icmp -- anywhere anywhere ACCEPT all -- anywhere anywhere ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:rich-cp ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:omnisky ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:5544 ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:must-backplane ACCEPT tcp -- anywhere anywhere state NEW tcp dpts:vrace:sec-t4net-srv ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:https ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:http ACCEPT udp -- anywhere anywhere state NEW udp dpt:5544 Chain FORWARD (policy ACCEPT)
4 Chain OUTPUT (policy ACCEPT) Specifically this line in the INPUT policy is what confirms the firewall rule exists: ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:5544 IF for some reason this firewall rule does not exist, you can add it with the following commands: iptables -I INPUT -p tcp --destination-port j ACCEPT service iptables save Lo g S e r ve r - C he c k Lo gs t a s h I s Running Assuming the config is correct, you may want to make sure that logstash is running: service logstash status Output similar to this is expected if it is running: Logstash Daemon (pid 1171) is running... Output similar to this is expected if it is NO T running: Logstash Daemon is stopped If it is not running, you should start it: service logstash start Lo g S e r ve r - C he c k Lo g S e r ve r I s Lis t e ning You want to make sure that the server is listening to port To check, execute the following command: netstat -nal grep 5544 Output similar to this is expected: tcp 0 0 :::5544 :::* LISTEN tcp 0 0 ::1:56104 ::1:5544 ESTABLISHED tcp 0 0 ::1:5544 ::1:56104 ESTABLISHED udp 0 0 :::5544 :::* IF it wasn't listening then there would be no output to that command OR the TCP ports would not appear. Follow this article to make sure Log Server is correctly configured: Documentation - Configuring Inputs Lo g S e r ve r - S e a r c h Lo g S e r ve r Da s hbo a r d To confirm the logs are being received you can search for the logs in the dashboard. Log into Log Server and click the Da s hb o a rd s menu. In the default dashboard we can search for the test logs we generated. In the Query field type: TroubleshootingTest Press Ente r and you should see the results below in the "Events Over Time" and "All Events" panels.
5 Lo g S e r ve r - C he c k Lo gs t a s h Lo g If you are still not seeing anything in the default dashboard you can check the logstash log file. Normally nothing is logged in here unless something goes wrong. To check, execute the following command: tail -f /var/log/logstash/logstash.log
6 Lo g S e r ve r - Lo gs Appe a r A Fe w Ho ur s La t e r It has been observed that you do not see the logs in the default dashboard you until a few hours after they were sent. In some situations the date and time is not correctly set on all t Log Server nodes. Follow this article to ensure the cluster timezone settings are correct: Documentation - Cluster Timezone Settings Lo g S e r ve r - Dis a ble Filt e r s An incorrectly typed filter can cause logs to not be processed by Log Server. A useful troubleshooting technique is to disable any extra filters you have added and see if the logs start appearing. Log into Log Server and click the Adminis tra tion n menu. Under Globab a l click Glo b a l C o nfig ura tio n On the right side of the screen is the Filters section. The default filter included in Nagios Log Server is Ap a c he (De fa ult) Disable any other filters you have added by clicking the Ac tive icon (it will turn into Inactive) Click the S a ve & Ap p ly button at the top Once you've disabled the filters, go to the Dashboards and see if logs start appearing. You will need to go through the process of enabling filters one-by-one (Save & Apply) each time until you identify the filter that is causing the issue. Once you know what filter is causin issue, you can investigate further into why there is an issue with this filter. Fina l Tho ught s For any support related questions please visit the Nagios Support Forums at: Posted by: tmcdonad o ld - Tue, Jan 27, 2015 at 5:41 PM. This article has been viewed 3020 times. Online URL:
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