# Debugging Cacti users sometimes complain about NaN's in their graphs. Unfortunately, there are several reasons for this result. The following is a step-by-step procedure recommended for debugging. ## Check Cacti Log File Your cacti log file should be located at `/log/cacti.log`. If it is not, see `Settings`, `Paths`. Check for this kind of error: ```console SPINE: Host[...] DS[....] WARNING: SNMP timeout detected [500 ms], ignoring host '........' ``` For "reasonable" timeouts, this may be related to a snmpbulkwalk issue. To change this, see `Settings`, `Poller` and lower the value for `The Maximum SNMP OIDs Per SNMP Get Request`. Start at a value of 2 and increase it again, if the poller starts working. (1 or less disables snmpbulkwalk) Some agent's don't have the horsepower to deliver that many OIDs at a time. Therefore, we can reduce the number for those older/under-powered devices. ## Check Basic Data Gathering For scripts, run them as cactiuser from CLI to check basic functionality. E.g. for a Perl script named `your-perl-script.pl` with parameters "p1 p2" under *nix this would look like: ```sh su - cactiuser /full/path/to/perl your-perl-script.pl p1 p2 ... (check output) ``` For SNMP, snmpget the _exact_ OID you're asking for, using same community string and SNMP version as defined within cacti. For an OID of `.1.3.6.1.4.something`, community string of `very-secret` and version 2 for target host `target-host` this would look like ```sh snmpget -c very-secret -v 2c target-host .1.3.6.1.4.something .... (check output) ``` ## Check Cacti's poller First make sure that crontab always shows poller.php. This program will either call cmd.php, the PHP based poller _or_ spine, the fast alternative, written in C. Define the poller you're using at `Settings`, `Poller`. Spine has to be implemented separately, it does not come with cacti by default. Now, clear `./log/cacti.log` (or rename it to get a fresh start) Then, change `Settings`, `Poller Logging Level` to DEBUG for _one_ polling cycle. You may rename this log as well to avoid more stuff added to it with subsequent polling cycles. Now, find the host/data source in question. The `Host[]` is given numerically, the `` being a specific number for that host. Find this `` from the `Devices` menu when editing the host: The URL contains a string like ```console id= ``` Check, whether the output is as expected. If not, check your script (e.g. `/full/path/to/perl`). If OK, proceed to next step This procedure may be replaced by running the poller manually for the failing host only. To do so, you need the ``, again. If you're using cmd.php, set the DEBUG logging level as defined above and run ```sh php -q cmd.php ``` If you're using spine, you may override logging level when calling the poller: ```sh ./spine --verbosity=5 ``` All output is printed to STDOUT in both cases. This procedure allows for repeated tests without waiting for the next polling interval. And there's no need to manually search for the failing host between hundreds of lines of output. ## Check MySQL updating In most cases, this step can be skipped. You may want to return to this step if the next one fails (e.g. no rrdtool update to be found) From debug log, find the MySQL update statement for that host concerning table `poller_output`. On very rare occasions, this will fail. Copy that SQL statement and paste it to a MySQL session started from CLI. This may as well be done from some tool like phpMyAdmin. Check the SQL return code. ## Check RRDfile updating Down in the same log, you should find some ```sh rrdtool update --template ... ``` You should find exactly one update statement for each file. RRDfiles should be created by the poller. If it does not create them, it will not fill them either. If it does check your `Poller Cache` from Utilities and search for your target. Does the query show up here? ## Check RRDfile ownership If RRDfiles were created e.g. with root ownership, a poller running as cactiuser will not be able to update those files ```sh cd /var/www/html/cacti/rra ls -l localhost* -rw-r--r-- 1 root root 463824 May 31 12:40 localhost_load_1min_5.rrd -rw-r--r-- 1 cactiuser cactiuser 155584 Jun 1 17:10 localhost_mem_buffers_3.rrd -rw-r--r-- 1 cactiuser cactiuser 155584 Jun 1 17:10 localhost_mem_swap_4.rrd -rw-r--r-- 1 cactiuser cactiuser 155584 Jun 1 17:10 localhost_proc_7.rrd -rw-r--r-- 1 cactiuser cactiuser 155584 Jun 1 17:10 localhost_users_6.rrd ``` Run the following command to cure this problem ```sh chown cactiuser:cactiuser *.rrd ``` ## Check RRDfile numbers You're perhaps wondering about this step, if the former was OK. But due to data sources MINIMUM and MAXIMUM definitions, it is possible, that valid updates for RRDfiles are suppressed, because MINIMUM was not reached or MAXIMUM was exceeded. Assuming, you've got some valid `rrdtool update` in step 3, perform a ```sh rrdtool fetch AVERAGE ``` and look at the last 10-20 lines. If you find NaN's there, perform ```sh rrdtool info ``` and check the `ds[...].min` and `ds[...].max` entries, e.g. ```sh ds[loss].min = 0.0000000000e+00 ds[loss].max = 1.0000000000e+02 ``` In this example, MINIMUM = 0 and MAXIMUM = 100. For a `ds.[...].type=GAUGE` verify, that e.g. the number returned by the script does not exceed `ds[...].MAX` (same holds for MINIMUM, respectively). If you run into this, not only should you update the data source definition within the Data Template, but also perform a: ```sh rrdtool tune --maximum : ``` for all existing RRDfiles belonging to that Data Template. At this step, it is wise to check `step` and `heartbeat` of the RRDfile as well. For standard 300 seconds polling intervals (step=300), it is wise to set `minimal_heartbeat` to 600 seconds. If a single update is missing and the next one occurs in less than 600 seconds from the last one, RRDtool will interpolate the missing update. Thus, gaps are "filled" automatically by interpolation. Be aware of the fact, that this is no "real" data! Again, this must be done in the Data Template itself and by using `rrdtool tune` for all existing RRDfiles of this type. ## Check `rrdtool graph` statement Last resort would be to check, that the correct data sources are used. Go to `Graph Management` and select your Graph. Enable DEBUG Mode to find the whole `rrdtool graph` statement. You should notice the `DEF` statements. They specify the RRDfile and data source to be used. You may check, that all of them are as wanted. ## Duplicate Poller Entries If you installed Cacti from a package (RPM, DEB, etc.), the package may have created both a cron entry in `/etc/cron.d/cacti` and enabled the `cactid` systemd service. Running two pollers simultaneously causes data corruption. Check for duplicate entries: ```sh systemctl status cactid cat /etc/cron.d/cacti cat /etc/crontab crontab -l -u cactiuser 2>/dev/null crontab -l -u root 2>/dev/null ``` The recommended approach is to use the `cactid` systemd service and remove any cron-based poller entries: ```sh systemctl enable --now cactid # Then remove or comment out any poller.php line in /etc/cron.d/cacti ``` If you need to keep cron-based polling, disable the service and leave a single cron entry: ```ini */5 * * * * cactiuser /usr/bin/php -q /var/www/html/cacti/poller.php > /dev/null 2>&1 ``` Replace `cactiuser` with the user your web server runs as (e.g. `www-data` on Debian/Ubuntu, `apache` on RHEL-compatible systems). ## Not NaN, but 0 (zero) values Pay attention to custom scripts. External commands called from there must be in the `$PATH` of the cactiuser running the poller. Use `/full/path/to/external/command` to avoid ambiguity. User "criggie" reported an issue with running smartctl. It was complaining "you are not root" so a quick `chmod +s` on the script fixed that problem. --- Copyright (c) 2004-2026 The Cacti Group