Correctly cast Darwin memory info (#1060)

* Correctly cast Darwin memory info

* Cast stats to float64 before doing math on them to avoid integer
wrapping.
* Remove invalid `_total` suffix from gauge values.
* Handle counters in `meminfo.go`.

Signed-off-by: Ben Kochie <superq@gmail.com>

3 files changed, 21 insertions, 10 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1401f84..a119177 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 ## master / unreleased
 
-**Breaking changes**
+### **Breaking changes**
 
 supvervisord collector reports "start_time_seconds" rather than "uptime"
 
@@ -8,6 +8,9 @@ The wifi collector is disabled by default due to suspected caching issues and go
 * https://github.com/prometheus/node_exporter/issues/870
 * https://github.com/prometheus/node_exporter/issues/1008
 
+Darwin meminfo metrics have been renamed to match Prometheus conventions. #1060
+
+### Changes
 * [CHANGE] Filter out non-installed units when collecting all systemd units #1011
 * [CHANGE] `service_restart_total` and `socket_refused_connections_total` will not be reported if you're running an older version of systemd
 * [FEATURE] Collect NRefused property for systemd socket units (available as of systemd v239)
@@ -19,6 +22,7 @@ The wifi collector is disabled by default due to suspected caching issues and go
 * [BUGFIX] Fix goroutine leak in supervisord collector
 * [BUGFIX] Systemd units will not be ignored if you're running older versions of systemd #1039
 * [BUGFIX] Handle vanishing PIDs #1043
+* [BUGFIX] Correctly cast Darwin memory info #1060
 
 ## 0.16.0 / 2018-05-15
 
diff --git a/collector/meminfo.go b/collector/meminfo.go
index ffe343a..1652b8b 100644
--- a/collector/meminfo.go
+++ b/collector/meminfo.go
@@ -18,6 +18,7 @@ package collector
 
 import (
         "fmt"
+        "strings"
 
         "github.com/prometheus/client_golang/prometheus"
         "github.com/prometheus/common/log"
@@ -41,19 +42,25 @@ func NewMeminfoCollector() (Collector, error) {
 // Update calls (*meminfoCollector).getMemInfo to get the platform specific
 // memory metrics.
 func (c *meminfoCollector) Update(ch chan<- prometheus.Metric) error {
+        var metricType prometheus.ValueType
         memInfo, err := c.getMemInfo()
         if err != nil {
                 return fmt.Errorf("couldn't get meminfo: %s", err)
         }
         log.Debugf("Set node_mem: %#v", memInfo)
         for k, v := range memInfo {
+                if strings.HasSuffix(k, "_total") {
+                        metricType = prometheus.CounterValue
+                } else {
+                        metricType = prometheus.GaugeValue
+                }
                 ch <- prometheus.MustNewConstMetric(
                         prometheus.NewDesc(
                                 prometheus.BuildFQName(namespace, memInfoSubsystem, k),
                                 fmt.Sprintf("Memory information field %s.", k),
                                 nil, nil,
                         ),
-                        prometheus.GaugeValue, v,
+                        metricType, v,
                 )
         }
         return nil
diff --git a/collector/meminfo_darwin.go b/collector/meminfo_darwin.go
index 0aa35ce..fc6b7b3 100644
--- a/collector/meminfo_darwin.go
+++ b/collector/meminfo_darwin.go
@@ -46,14 +46,14 @@ func (c *meminfoCollector) getMemInfo() (map[string]float64, error) {
         // Syscall removes terminating NUL which we need to cast to uint64
         total := binary.LittleEndian.Uint64([]byte(totalb + "\x00"))
 
-        ps := C.natural_t(syscall.Getpagesize())
+        ps := float64(C.natural_t(syscall.Getpagesize()))
         return map[string]float64{
-                "active_bytes_total":      float64(ps * vmstat.active_count),
-                "inactive_bytes_total":    float64(ps * vmstat.inactive_count),
-                "wired_bytes_total":       float64(ps * vmstat.wire_count),
-                "free_bytes_total":        float64(ps * vmstat.free_count),
-                "swapped_in_pages_total":  float64(ps * vmstat.pageins),
-                "swapped_out_pages_total": float64(ps * vmstat.pageouts),
-                "bytes_total":             float64(total),
+                "active_bytes":            ps * float64(vmstat.active_count),
+                "inactive_bytes":          ps * float64(vmstat.inactive_count),
+                "wired_bytes":             ps * float64(vmstat.wire_count),
+                "free_bytes":              ps * float64(vmstat.free_count),
+                "swapped_in_bytes_total":  ps * float64(vmstat.pageins),
+                "swapped_out_bytes_total": ps * float64(vmstat.pageouts),
+                "total_bytes":             float64(total),
         }, nil
 }