The error, Logs Not Searchable or Not Coming In Nagios Log Server occur while we run a query in a dashboard.
As part of our Server Management Services, we assist our customers with several Nagios errors.
Today, let’s find out a problematic solution suggested by our experienced Server Admins.
Logs Not Searchable or Not Coming In Nagios Log Server
As we mentioned earlier, while we run a query in a dashboard, logs may not show up when they should. In this article, we will use a scenario of a remote server sending
syslogs- Log Server
Name: nls-c7x-x64
IP: 10.25.5.86
Listening Port: TCP 5544
- Remote Server Sending Logs
Name: centos12
IP: 10.25.13.30
Sending Port: TCP 5544
OS: CentOS 6.7 x64
Furthermore, let us focus on the methods our Support Techs employ in order to fix Logs Not Searchable or Not Coming In Nagios Log Server.
Remote Server – Check Rsyslog Config
This server has already been set up to send logs to
nls-c7x-x64To confirm this has been done, we create a file and it contains:
/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. 192.168.0.1:514, port optional NAGIOSLOGSERVER *.* @@nls-c7x-x64:5544 # NAGIOSLOGSERVER ### End of Nagios Log Server forwarding rule NAGIOSLOGSERVERIt is important to note here the following line:
*.* @@nls-c7x-x64:5544 # NAGIOSLOGSERVERIt is assumed that the server centos12 can resolve the address
, otherwise, it will not be able to send it logs.nls-c7x-x64To confirm this, we execute the following command on centos12:
ping nls-c7x-x64 -c 1We expect an output similar to this if it can successfully resolve
:nls-c7x-x64PING nls-c7x-x64.box293.local (10.25.5.86) 56(84) bytes of data. 64 bytes from nls-c7x-x64.box293.local (10.25.5.86): icmp_seq=1 ttl=64 time=0.273 ms — nls-c7x-x64.box293.local ping statistics — 1 packets transmitted, 1 received, 0% packet loss, time 2ms rtt min/avg/max/mdev = 0.273/0.273/0.273/0.000 msOn the other hand, we can expect an output similar to this if it cannot resolve
:nls-c7x-x64ping: unknown host nls-c7x-x64Going back to that config line:
*.* @@nls-c7x-x64:5544 # NAGIOSLOGSERVERThe @@ indicates that the port type is TCP and the port number is 5544.
If it was UDP, there would only be one @.
Remote Server – Check Rsyslog Is Running
Assuming the config is correct, we may want to make sure that
is running:rsyslogdservice rsyslog statusWe can expect an output like this if it is running:
rsyslogd (pid 2098) is running…Also, we can expect an output similar to this is if it is not running:
rsyslogd is stoppedSubsequently, if it is not running, we should start it:
service rsyslog start
Remote Server – Check Firewall Rules
We want to make sure that the
firewall allows outbound traffic. By default, there are no restrictions on outbound traffic.iptablesTo confirm this, we execute the following command:
iptables –listWe expect an output similar to this:
Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT all — anywhere anywhere state RELATED,ESTABLISHED ACCEPT icmp — anywhere anywhere ACCEPT all — anywhere anywhere ACCEPT tcp — anywhere anywhere state NEW tcp dpt:ssh REJECT all — anywhere anywhere reject-with icmp-host-prohibited Chain FORWARD (policy ACCEPT) target prot opt source destination REJECT all — anywhere anywhere reject-with icmp-host-prohibited Chain OUTPUT (policy ACCEPT) target prot opt source destinationSpecifically, this last output is what we need to look at:
Chain OUTPUT (policy ACCEPT) target prot opt source destinationThe first line has (ACCEPT) 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 ACCEPT all outbound traffic (allow it).
If we had a restricted environment where outbound rules were DROP, we would need to add an outbound firewall rule for TCP port 5544 to nls-c7x-x64 on 10.25.5.86:
iptables -I OUTPUT -p tcp –destination-port 5544 -d 10.25.5.86 -j ACCEPT service iptables save
Remote Server – Watch Outbound Traffic
To confirm that the log traffic is leaving the remote server we can run a
to watch the traffic.tcpdumpFirst, we must install
:tcpdumpyum -y install tcpdumpWait while
is installed.tcpdumpNow we execute the following command to watch the traffic:
tcpdump src host 10.25.13.30 and tcp dst port 5544 and dst host 10.25.5.86We will 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 65535 bytesAn example of traffic flow is as follows:
16:43:49.001130 IP centos12.box293.local.60907 > nls-c7x-x64.box293.local.5544: Flags [P.], seq 2751017526:2751017581, ack 431734015, win 115, options [nop,nop,TS val 93111400 ecr 92667575], length 55If we do not see any traffic, nothing is being logged and hence there is nothing to send. We can easily add a test entry to
which will generate traffic:rsyslog
- Open an additional ssh session to the remote server
- Execute the following command:
logger TroubleshootingTestIn our other SSH session, we should now see a line of traffic that confirms that
is sending the logs ontorsyslog.nls-c7x-x64Press Ctrl C to stop the
.tcpdump
Log Server – Watch Inbound Traffic
To confirm that the log traffic is entering the log server we can run a
This is similar to the previous steps except it confirms that the traffic has made through any routers or firewalls between the remote server and the log server.tcpdump.First, we must install
with this command:tcpdumpRHEL|CentOS
yum install -y tcpdumpDebian|Ubuntu
apt-get install -y tcpdumpNow we execute the following command to watch the traffic:
tcpdump src host 10.25.13.30 and tcp dst port 5544 and dst host 10.25.5.86We will 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 65535 bytesAn example of traffic flow is as follows:
16:52:42.509481 IP centos12.box293.local.60907 > nls-c7x-x64.box293.local.5544: Flags [P.], seq 2751017651:2751017706, ack 431734015, win 115, options [nop,nop,TS val 93644443 ecr 92674681], length 55If we do not see any traffic, it may just be that nothing is being logged and hence there is nothing to send. We can easily add a test entry to
which will generate traffic:rsyslog
- Open an additional ssh session to the remote server
- Execute the following command:
logger TroubleshootingTestIn our log server SSH session, we should now see a line of traffic that confirms that the traffic is hitting the log server.
Press Ctrl C to stop the
.tcpdumpIf we do not see any traffic, then there may be a firewall or router blocking the traffic.
Log Server – Check Firewall Rules
We want to make sure that the
firewall allows inbound traffic. By default there are restrictions on inbound traffic however Nagios Log Server creates the firewall rules to allow the traffic.iptables
-
RHEL 6|CentOS 6
There are separate firewall daemons for IPv4 and IPv6 and hence our Support Techs suggest separate commands.
First, check the status of the firewall:
IPv4
service iptables statusIPv6
service ip6tables statusIf the firewall is running, it should produce output like:
Table: filter Chain INPUT (policy ACCEPT) num target prot opt source destination 1 ACCEPT all — 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 2 ACCEPT icmp — 0.0.0.0/0 0.0.0.0/0 3 ACCEPT all — 0.0.0.0/0 0.0.0.0/0 4 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22 5 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:2057 6 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:2056 7 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:5544 8 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:3515 9 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpts:9300:9400 10 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:443 11 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:80 12 ACCEPT udp — 0.0.0.0/0 0.0.0.0/0 state NEW udp dpt:5544 13 REJECT all — 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited Chain FORWARD (policy ACCEPT) num target prot opt source destination 1 REJECT all — 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited Chain OUTPUT (policy ACCEPT) num target prot opt source destinationSpecifically, these lines tell us that the firewall rule exists and is allowing inbound UDP and TCP traffic on port 5544:
7 ACCEPT tcp — 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:5544 12 ACCEPT udp — 0.0.0.0/0 0.0.0.0/0 state NEW udp dpt:554If these firewall rules do not exist, we add them by executing the following commands:
IPv4
iptables -I INPUT -p udp –dport 5544 -j ACCEPT iptables -I INPUT -p tcp –dport 5544 -j ACCEPT service iptables saveIPv6
ip6tables -I INPUT -p udp –dport 5544 -j ACCEPT ip6tables -I INPUT -p tcp –dport 5544 -j ACCEPT service ip6tables saveIf the firewall is not running, it will produce this output:
iptables: Firewall is not running.If the firewall is not running, this means that inbound traffic is allowed.
To enable the firewall on boot and to start it, we execute the following commands:
IPv4
chkconfig iptables on service iptables startIPv6
chkconfig ip6tables on service ip6tables start
-
RHEL 7|CentOS 7
First, check the status of the firewall:
systemctl status firewalld.serviceIf the firewall is running, it should produce output like:
● firewalld.service – firewalld – dynamic firewall daemon Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled) Active: active (running) since Thu 2018-12-13 11:16:59 AEDT; 39min ago Docs: man:firewalld(1) Main PID: 670 (firewalld) CGroup: /system.slice/firewalld.service └─670 /usr/bin/python -Es /usr/sbin/firewalld –nofork –nopidSimilarly, if the firewall is not running, it will produce this output:
● firewalld.service – firewalld – dynamic firewall daemon Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled) Active: inactive (dead) since Thu 2018-12-13 11:57:15 AEDT; 1s ago Docs: man:firewalld(1) Process: 670 ExecStart=/usr/sbin/firewalld –nofork –nopid $FIREWALLD_ARGS (code=exited, status=0/SUCCESS) Main PID: 670 (code=exited, status=0/SUCCESS)If the firewall is not running, this means that inbound traffic is allowed.
To enable the firewall on boot and to start it, we execute the following commands:
systemctl enable firewalld.service systemctl start firewalld.serviceTo list the firewall rules execute this command:
firewall-cmd –list-allWhich should produce output like:
public (active) target: default icmp-block-inversion: no interfaces: ens32 sources: services: dhcpv6-client ssh ports: 80/tcp 443/tcp 9300-9400/tcp 3515/tcp 5544/tcp 2056/tcp 2057/tcp 5544/udp protocols: masquerade: no forward-ports: source-ports: icmp-blocks: rich rules:Specifically, the ports line tells us that the firewall rule exists and is allowing inbound UDP and TCP traffic on port 5544:
ports: 80/tcp 443/tcp 9300-9400/tcp 3515/tcp 5544/tcp 2056/tcp 2057/tcp 5544/udpIf these firewall rules do not exist, they can be added by executing the following commands:
firewall-cmd –zone=public –add-port=5544/udp firewall-cmd –zone=public –add-port=5544/tcp firewall-cmd –reload
-
Debian
Debian has the
iptablesnetfilter-persistent serviceWe can determine if it is installed with the following command:
systemctl status netfilter-persistent.serviceIf we receive this output then there is no firewall service active on our Debian machine:
Unit netfilter-persistent.service could not be found.This means all inbound traffic is allowed, we will receive SNMP Traps.
If we receive this output then the firewall service is active on our Debian machine:
● netfilter-persistent.service – netfilter persistent configuration Loaded: loaded (/lib/systemd/system/netfilter-persistent.service; enabled) Active: active (exited) since Tue 2018-11-27 14:24:11 AEDT; 1min 26s ago Main PID: 17749 (code=exited, status=0/SUCCESS)If the
is enabled we can now check the status of the firewall:netfilter-persistent serviceiptables –listAn open firewall-config would produce output like:
Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destinationWe can see no rules exist.
If a rule did exist allowing inbound UDP traffic on port 162 then it would look like this:
target prot opt source destination ACCEPT udp — anywhere anywhere udp dpt:snmp-trapIf these firewall rules do not exist, they can be added by executing the following commands:
iptables -I INPUT -p udp –destination-port 5544 -j ACCEPT iptables -I INPUT -p tcp –destination-port 5544 -j ACCEPT
-
Ubuntu
Ubuntu uses the Uncomplicated Firewall (
ufwWe can check it with the following command:
ufw statusIf the firewall is not running, it will produce this output:
Status: inactiveMeanwhile, if the firewall is running, it should produce output like:
Status: activeIf the firewall is not running, this means that inbound traffic is allowed (we will receive SNMP Traps).
To enable the firewall on boot and to start it, we execute the following command:
ufw enableBe careful executing this command, we will not be able to access the server when it next reboots. Its default configuration is to deny all incoming connections. We will need to add rules for all the different ports connect to this server.
To list the firewall rules we execute this command:
ufw status verboseWhich should produce output like:
Status: active Logging: on (low) Default: deny (incoming), allow (outgoing), disabled (routed) New profiles: skip To Action From — —— —- 5544/udp ALLOW IN Anywhere 5544/tcp ALLOW IN Anywhere 5544/udp (v6) ALLOW IN Anywhere (v6) 5544/tcp (v6) ALLOW IN Anywhere (v6)We can see from the output that firewall rules exist allowing inbound UDP and TCP traffic on port 5544.
If these firewall rules do not exist, they can be added by executing the following commands:
ufw allow proto udp from any to any port 5544 ufw allow proto tcp from any to any port 5544 ufw reload
Log Server – Check Logstash Is Running
Assuming the config is correct, we may want to make sure that
is running:logstashRHEL 6|CentOS 6|Ubuntu 14
service logstash statusRHEL 7|CentOS 7|Debian|Ubuntu 16/18
systemctl status logstash.serviceWe can expect an output similar to this if it is running:
Logstash Daemon (pid 1171) is running…We can expect an output similar to this if it is not running:
Logstash Daemon is stoppedIf it is not running, we should start it:
RHEL 6|CentOS 6|Ubuntu 14
service logstash startRHEL 7|CentOS 7|Debian|Ubuntu 16/18
systemctl start logstash.service
Log Server – Check Log Server Is Listening
We want to make sure that the server is listening to port 5544. To check, we execute the following command:
netstat -nal | grep 5544We can expect an output similar to:
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 was not listening, then there would be no output to that command or the TCP ports would not appear.
Log Server – Search Log Server Dashboard
To confirm the logs are being received, we can search for the logs in the dashboard.
Initially, we log into the Log Server and click the Dashboards menu.
In the default dashboard we can search for the test logs we generated.
In the Query field type:
TroubleshootingTestPress Enter and we should see the results below in the “Events Over Time” and “All Events” panels:
Log Server – Check Logstash Log
If we are still not seeing anything in the default dashboard we can check the
log file. Usually, nothing logs in here unless something goes wrong.logstashTo check, we execute the following command:
tail -f /var/log/logstash/logstash.log
Log Server – Logs Appear A Few Hours Later
We do not see the logs in the default dashboard until a few hours after they were sent. In some situations, the date and time are not set correctly on all the Nagios Log Server nodes.
To ensure that the cluster timezone settings are correct, we follow the steps given below:
- Log into Nagios Log Server
- In the top menu bar click Admin
- Under General click Global Settings
- Here we can define the Cluster Timezone
- If it is not correct, select the timezone and click Save Settings
Log Server – Disable Filters
An incorrect filter can cause logs to not process by Log Server. A useful troubleshoot is to disable any extra filters we have added and see if the logs start appearing.
- Log into Log Server and click Configure
- Under Global (All Instances) click Global Config
- On the right side of the screen is the Filters section
- The default filter included in Nagios Log Server is Apache
- Disable any other filters we have added by clicking the Active icon (it will turn into Inactive)
- Click the Save & Apply button at the top
Once we have disabled the filters, we go to the Dashboards and see if logs start appearing.
We will need to go through the process of enabling filters one-by-one (Save & Apply) each time until we identify the filter that is causing the issue. Once we know what filter is causing the issue, we can investigate why there is an issue with this filter.
[Error continues to prevail? We’d be happy to assist!]
Conclusion
To conclude, Logs Not Searchable or Not Coming In Nagios Log Server occur while we run a query in a dashboard. Today, we saw effective methods our Support Engineers employ in order to fix this error.
