1 files changed, 89 insertions, 0 deletions
diff --git a/src/go/collectors/go.d.plugin/modules/isc_dhcpd/collect.go b/src/go/collectors/go.d.plugin/modules/isc_dhcpd/collect.go
new file mode 100644
index 000000000..6930e8770
--- /dev/null
+++ b/src/go/collectors/go.d.plugin/modules/isc_dhcpd/collect.go
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package isc_dhcpd
+
+import (
+	"os"
+)
+
+/*
+dhcpd.leases db (file), see details: https://kb.isc.org/docs/en/isc-dhcp-44-manual-pages-dhcpdleases#dhcpdleases
+
+Every time a lease is acquired, renewed or released, its new value is recorded at the end of the lease file.
+So if more than one declaration appears for a given lease, the last one in the file is the current one.
+
+In order to prevent the lease database from growing without bound, the file is rewritten from time to time.
+First, a temporary lease database is created and all known leases are dumped to it.
+Then, the old lease database is renamed DBDIR/dhcpd.leases~.
+Finally, the newly written lease database is moved into place.
+
+In order to process both DHCPv4 and DHCPv6 messages you will need to run two separate instances of the dhcpd process.
+Each of these instances will need its own lease file.
+*/
+
+func (d *DHCPd) collect() (map[string]int64, error) {
+	fi, err := os.Stat(d.LeasesPath)
+	if err != nil {
+		return nil, err
+	}
+
+	if d.leasesModTime.Equal(fi.ModTime()) {
+		d.Debugf("leases file is not modified, returning cached metrics ('%s')", d.LeasesPath)
+		return d.collected, nil
+	}
+
+	d.leasesModTime = fi.ModTime()
+
+	leases, err := parseDHCPdLeasesFile(d.LeasesPath)
+	if err != nil {
+		return nil, err
+	}
+
+	activeLeases := removeInactiveLeases(leases)
+	d.Debugf("found total/active %d/%d leases ('%s')", len(leases), len(activeLeases), d.LeasesPath)
+
+	for _, pool := range d.pools {
+		collectPool(d.collected, pool, activeLeases)
+	}
+	d.collected["active_leases_total"] = int64(len(activeLeases))
+
+	return d.collected, nil
+}
+
+const precision = 100
+
+func collectPool(collected map[string]int64, pool ipPool, leases []leaseEntry) {
+	n := calcPoolActiveLeases(pool, leases)
+	collected["pool_"+pool.name+"_active_leases"] = n
+	collected["pool_"+pool.name+"_utilization"] = int64(calcPoolUtilizationPercentage(pool, n) * precision)
+}
+
+func calcPoolActiveLeases(pool ipPool, leases []leaseEntry) (num int64) {
+	for _, l := range leases {
+		if pool.addresses.Contains(l.ip) {
+			num++
+		}
+	}
+	return num
+}
+
+func calcPoolUtilizationPercentage(pool ipPool, leases int64) float64 {
+	size := pool.addresses.Size()
+	if leases == 0 || !size.IsInt64() {
+		return 0
+	}
+	if size.Int64() == 0 {
+		return 100
+	}
+	return float64(leases) / float64(size.Int64()) * 100
+}
+
+func removeInactiveLeases(leases []leaseEntry) (active []leaseEntry) {
+	active = leases[:0]
+	for _, l := range leases {
+		if l.bindingState == "active" {
+			active = append(active, l)
+		}
+	}
+	return active
+}