This package provides an access to systemd via D-Bus
to list services (think systemctl list-units) with a low overhead for a caller.
If you find the API too limiting or missing some of functionality,
perhaps https://github.com/coreos/go-systemd might suit you better.
c, err := systemd.New()
if err != nil {
log.Fatal(err)
}
defer c.Close()
err = c.ListUnits(systemd.IsService, func(u *systemd.Unit) {
fmt.Printf("%s %s\n", u.Name, u.ActiveState)
})
if err != nil {
log.Fatal(err)
}
// Output:
// dirmngr.service inactive
// dbus.service active
// snapd.session-agent.service inactive
// gpg-agent.service inactive
// pk-debconf-helper.service inactiveCheck out units program to see how to get PIDs of services.
$ go run ./cmd/units -svc
0 dirmngr.service inactive
2375 dbus.service active
0 snapd.session-agent.service inactive
0 gpg-agent.service inactive
0 pk-debconf-helper.service inactiveYou can get the same results with dbus-send.
$ dbus-send --system --print-reply --dest=org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager.ListUnits
$ dbus-send --system --print-reply --dest=org.freedesktop.systemd1 /org/freedesktop/systemd1/unit/dbus_2eservice org.freedesktop.DBus.Properties.Get string:'org.freedesktop.systemd1.Service' string:'MainPID'Run tests and linters.
$ go test -v -count=1 .
$ golangci-lint runBenchmarks help to spot performance changes and troubleshoot performance issues. For example, you can see where and how much memory gets allocated when a 35KB D-Bus ListUnits reply is decoded into 157 Unit structs.
$ go test -run=^$ -bench=^BenchmarkDecodeListUnits$ -benchmem -memprofile list_units.allocs
$ go tool pprof list_units.allocsIt is recommended to run benchmarks multiple times and check how stable they are using Benchstat tool.
$ go test -timeout 20m -bench=. -benchmem -count=50 . | tee bench-new.txt
$ benchstat bench-new.txtThe old and new stats are compared as follows.
$ benchstat bench-old.txt bench-new.txt
$ benchstat bench-old.txt bench-new.txtname old time/op new time/op delta
AuthExternal-2 475ns ± 2% 467ns ± 2% -1.72% (p=0.000 n=46+45)
DecodeString-2 54.3ns ± 3% 53.4ns ± 4% -1.67% (p=0.000 n=49+50)
EscapeBusLabel-2 43.8ns ± 2% 43.2ns ± 2% -1.35% (p=0.000 n=48+50)
DecodeHeader-2 340ns ± 4% 340ns ±12% -0.17% (p=0.017 n=48+45)
EncodeHeader-2 185ns ± 1% 187ns ± 3% +1.28% (p=0.000 n=48+49)
EncodeHello-2 224ns ± 2% 221ns ± 3% -1.03% (p=0.000 n=46+50)
DecodeHello-2 122ns ± 4% 84ns ±11% -31.21% (p=0.000 n=49+49)
EncodeMainPID-2 383ns ± 4% 383ns ± 3% ~ (p=0.548 n=43+48)
DecodeMainPID-2 140ns ± 2% 96ns ± 3% -31.63% (p=0.000 n=48+50)
EncodeListUnits-2 234ns ± 2% 236ns ± 2% +0.61% (p=0.001 n=41+47)
DecodeListUnits-2 92.9µs ± 2% 92.5µs ± 5% -0.39% (p=0.028 n=48+45)
name old alloc/op new alloc/op delta
AuthExternal-2 80.0B ± 0% 80.0B ± 0% ~ (all equal)
DecodeString-2 0.00B 0.00B ~ (all equal)
EscapeBusLabel-2 0.00B 0.00B ~ (all equal)
DecodeHeader-2 15.0B ± 0% 15.0B ± 0% ~ (all equal)
EncodeHeader-2 0.00B 0.00B ~ (all equal)
EncodeHello-2 0.00B 0.00B ~ (all equal)
DecodeHello-2 29.0B ± 0% 5.0B ± 0% -82.76% (p=0.000 n=50+50)
EncodeMainPID-2 45.0B ± 0% 45.0B ± 0% ~ (all equal)
DecodeMainPID-2 24.0B ± 0% 0.0B -100.00% (p=0.000 n=50+50)
EncodeListUnits-2 0.00B 0.00B ~ (all equal)
DecodeListUnits-2 21.0kB ± 0% 20.9kB ± 0% -0.11% (p=0.000 n=50+50)
name old allocs/op new allocs/op delta
AuthExternal-2 3.00 ± 0% 3.00 ± 0% ~ (all equal)
DecodeString-2 0.00 0.00 ~ (all equal)
EscapeBusLabel-2 0.00 0.00 ~ (all equal)
DecodeHeader-2 0.00 0.00 ~ (all equal)
EncodeHeader-2 0.00 0.00 ~ (all equal)
EncodeHello-2 0.00 0.00 ~ (all equal)
DecodeHello-2 1.00 ± 0% 0.00 -100.00% (p=0.000 n=50+50)
EncodeMainPID-2 0.00 0.00 ~ (all equal)
DecodeMainPID-2 1.00 ± 0% 0.00 -100.00% (p=0.000 n=50+50)
EncodeListUnits-2 0.00 0.00 ~ (all equal)
DecodeListUnits-2 6.00 ± 0% 5.00 ± 0% -16.67% (p=0.000 n=50+50)
When there is a statistically significant improvement, please update bench-old.txt and the benchmark results above.
$ cp bench-new.txt bench-old.txt