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Don't race in FreeBSD devstat collector

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Querying the number of devices separately from the device list itself is
racy. Devices may be added or removed between the two calls; and removed
devices would lead to a segfault.
This commit is contained in:
Dominik Honnef 2016-12-31 06:52:44 +01:00
commit ea55d0f5cb
3 changed files with 71 additions and 72 deletions
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42
collector/devstat_freebsd.go
View file

@ -18,6 +18,7 @@ package collector
import (
"errors"
"fmt"
"unsafe"
"github.com/prometheus/client_golang/prometheus"
)
@ -75,25 +76,30 @@ func NewDevstatCollector() (Collector, error) {
}, nil
}
func (c *devstatCollector) Update(ch chan<- prometheus.Metric) (err error) {
count := C._get_ndevs()
if count == -1 {
return errors.New("devstat_getdevs() failed")
func (c *devstatCollector) Update(ch chan<- prometheus.Metric) error {
var stats *C.Stats
n := C._get_stats(&stats)
if n == -1 {
return errors.New("devstat_getdevs failed")
}
for i := C.int(0); i < count; i++ {
stats := C._get_stats(i)
device := fmt.Sprintf("%s%d", C.GoString(&stats.device[0]), stats.unit)
ch <- c.bytes.mustNewConstMetric(float64(stats.bytes.read), device, "read")
ch <- c.bytes.mustNewConstMetric(float64(stats.bytes.write), device, "write")
ch <- c.transfers.mustNewConstMetric(float64(stats.transfers.other), device, "other")
ch <- c.transfers.mustNewConstMetric(float64(stats.transfers.read), device, "read")
ch <- c.transfers.mustNewConstMetric(float64(stats.transfers.write), device, "write")
ch <- c.duration.mustNewConstMetric(float64(stats.duration.other), device, "other")
ch <- c.duration.mustNewConstMetric(float64(stats.duration.read), device, "read")
ch <- c.duration.mustNewConstMetric(float64(stats.duration.write), device, "write")
ch <- c.busyTime.mustNewConstMetric(float64(stats.busyTime), device)
ch <- c.blocks.mustNewConstMetric(float64(stats.blocks), device)
base := unsafe.Pointer(stats)
for i := C.int(0); i < n; i++ {
offset := i * C.int(C.sizeof_Stats)
stat := (*C.Stats)(unsafe.Pointer(uintptr(base) + uintptr(offset)))
device := fmt.Sprintf("%s%d", C.GoString(&stat.device[0]), stat.unit)
ch <- c.bytes.mustNewConstMetric(float64(stat.bytes.read), device, "read")
ch <- c.bytes.mustNewConstMetric(float64(stat.bytes.write), device, "write")
ch <- c.transfers.mustNewConstMetric(float64(stat.transfers.other), device, "other")
ch <- c.transfers.mustNewConstMetric(float64(stat.transfers.read), device, "read")
ch <- c.transfers.mustNewConstMetric(float64(stat.transfers.write), device, "write")
ch <- c.duration.mustNewConstMetric(float64(stat.duration.other), device, "other")
ch <- c.duration.mustNewConstMetric(float64(stat.duration.read), device, "read")
ch <- c.duration.mustNewConstMetric(float64(stat.duration.write), device, "write")
ch <- c.busyTime.mustNewConstMetric(float64(stat.busyTime), device)
ch <- c.blocks.mustNewConstMetric(float64(stat.blocks), device)
}
return err
C.free(unsafe.Pointer(stats))
return nil
}