Extends uname collector to export on Darwin OS (#1433)

Adds uname collector support for Darwin and OpenBSD

Signed-off-by: Philip Gough <philip.p.gough@gmail.com>

README.md

@@ -57,7 +57,7 @@ stat | Exposes various statistics from `/proc/stat`. This includes boot time, fo
 textfile | Exposes statistics read from local disk. The `--collector.textfile.directory` flag must be set. | _any_
 time | Exposes the current system time. | _any_
 timex | Exposes selected adjtimex(2) system call stats. | Linux
-uname | Exposes system information as provided by the uname system call. | FreeBSD, Linux
+uname | Exposes system information as provided by the uname system call. | Darwin, FreeBSD, Linux, OpenBSD
 vmstat | Exposes statistics from `/proc/vmstat`. | Linux
 xfs | Exposes XFS runtime statistics. | Linux (kernel 4.4+)
 zfs | Exposes [ZFS](http://open-zfs.org/) performance statistics. | [Linux](http://zfsonlinux.org/), Solaris

collector/uname.go

@@ -11,7 +11,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build freebsd linux
+// +build darwin freebsd openbsd linux
 // +build !nouname
 
 package collector

collector/uname_bsd.go

@@ -11,6 +11,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build darwin freebsd openbsd
 // +build !nouname
 
 package collector
@@ -28,30 +29,35 @@ func getUname() (uname, error) {
 		return uname{}, err
 	}
 
-	// We do a little bit of work here to emulate what happens in the Linux
-	// uname calls since FreeBSD uname doesn't have a Domainname.
+	nodeName, domainName := parseHostNameAndDomainName(utsname)
+
+	output := uname{
+		SysName:    string(utsname.Sysname[:bytes.IndexByte(utsname.Sysname[:], 0)]),
+		Release:    string(utsname.Release[:bytes.IndexByte(utsname.Release[:], 0)]),
+		Version:    string(utsname.Version[:bytes.IndexByte(utsname.Version[:], 0)]),
+		Machine:    string(utsname.Machine[:bytes.IndexByte(utsname.Machine[:], 0)]),
+		NodeName:   nodeName,
+		DomainName: domainName,
+	}
+
+	return output, nil
+}
+
+// parseHostNameAndDomainName for FreeBSD,OpenBSD,Darwin.
+// Attempts to emulate what happens in the Linux uname calls since these OS doesn't have a Domainname.
+func parseHostNameAndDomainName(utsname unix.Utsname) (hostname string, domainname string) {
 	nodename := string(utsname.Nodename[:bytes.IndexByte(utsname.Nodename[:], 0)])
 	split := strings.SplitN(nodename, ".", 2)
 
 	// We'll always have at least a single element in the array. We assume this
 	// is the hostname.
-	hostname := split[0]
+	hostname = split[0]
 
 	// If we have more than one element, we assume this is the domainname.
 	// Otherwise leave it to "(none)" like Linux.
-	domainname := "(none)"
+	domainname = "(none)"
 	if len(split) > 1 {
 		domainname = split[1]
 	}
-
-	output := uname{
-		SysName:    string(utsname.Sysname[:bytes.IndexByte(utsname.Sysname[:], 0)]),
-		Release:    string(utsname.Release[:bytes.IndexByte(utsname.Release[:], 0)]),
-		Version:    string(utsname.Version[:bytes.IndexByte(utsname.Version[:], 0)]),
-		Machine:    string(utsname.Machine[:bytes.IndexByte(utsname.Machine[:], 0)]),
-		NodeName:   hostname,
-		DomainName: domainname,
-	}
-
-	return output, nil
+	return hostname, domainname
 }