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95 lines
2.8 KiB
Markdown
95 lines
2.8 KiB
Markdown
source: Extensions/Fast-Ping-Check.md
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path: blob/master/doc/
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# Fast up/down checking
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Normally, LibreNMS sends an ICMP ping to the device before polling to
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check if it is up or down. This check is tied to the poller frequency,
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which is normally 5 minutes. This means it may take up to 5 minutes
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to find out if a device is down.
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Some users may want to know if devices stop responding to ping more
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quickly than that. LibreNMS offers a ping.php script to run ping
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checks as quickly as possible without increasing snmp load on your
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devices by switching to 1 minute polling.
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**WARNING**: If you do not have an alert rule that alerts on device
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status, enabling this will be a waste of resources. You can find one
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in the [Alert Rules
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Collection](../Alerting/Rules.md#alert-rules-collection).
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## Setting the ping check to 1 minute
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1: Change the ping_rrd_step setting in config.php
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```
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$config['ping_rrd_step'] = 60;
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```
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2: Update the rrd files to change the step (step is hardcoded at file
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creation in rrd files)
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```
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./scripts/rrdstep.php -h all
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```
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3: Add the following line to /etc/cron.d/librenms to allow 1 minute
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ping checks
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```
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* * * * * librenms /opt/librenms/ping.php >> /dev/null 2>&1
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```
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**NOTE**: If you are using distributed pollers you can restrict a
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poller to a group by appending `-g` to the cron entry. Alternatively,
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you should only run ping.php on a single node.
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## Sub minute ping check
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Cron only has a resolution of one minute, so we have to use a trick to
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allow sub minute checks. We add two entries, but add a delay before one.
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Alerts are only run every minute, so you will have to modify them as
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well. Remove the original alerts.php entry.
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1: Set ping_rrd_step
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```
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$config['ping_rrd_step'] = 30;
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```
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2: Update the rrd files
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```
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./scripts/rrdstep.php -h all
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```
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3: Update cron (removing any other ping.php or alert.php entries)
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```
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* * * * * librenms /opt/librenms/ping.php >> /dev/null 2>&1
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* * * * * librenms sleep 30 && /opt/librenms/ping.php >> /dev/null 2>&1
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* * * * * librenms sleep 15 && /opt/librenms/alerts.php >> /dev/null 2>&1
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* * * * * librenms sleep 45 && /opt/librenms/alerts.php >> /dev/null 2>&1
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```
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# Device dependencies
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The ping.php script respects device dependencies, but the main poller
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does not (for technical reasons). However, using this script does not
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disable the icmp check in the poller and a child may be reported as
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down before the parent.
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# Settings
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ping.php uses much the same settings as the poller fping with one
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exception: retries is used instead of count.
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ping.php does not measure loss and avg response time, only up/down, so
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once a device responds it stops pinging it.
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```
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$config['fping_options']['retries'] = 2;
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$config['fping_options']['timeout'] = 500;
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$config['fping_options']['interval'] = 500;
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```
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