Print system information (uname) at Prometheus startup (#2709)

* Print uname on prom startup

* Make uname file linux-only

* Add missing license headers

Add missing license headers

* Print OS when uname is not available

* Print only OS name when uname not available

* Remove extra space, fix cmd/prometheus/main.go license header

* Add fix for int8 and uint8 systems

* Better formatting for build tags in cmd/prometheus/uname files

* Remove newline

cmd/prometheus/main.go

@@ -87,6 +87,7 @@ func Main() int {
 
 	log.Infoln("Starting prometheus", version.Info())
 	log.Infoln("Build context", version.BuildContext())
+	log.Infoln("Host details", Uname())
 
 	var (
 		sampleAppender = storage.Fanout{}

cmd/prometheus/uname_default.go

@@ -0,0 +1,23 @@
+// Copyright 2017 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !linux
+
+package main
+
+import "runtime"
+
+// Uname for any platform other than linux.
+func Uname() string {
+	return "(" + runtime.GOOS + ")"
+}

cmd/prometheus/uname_linux.go

@@ -0,0 +1,35 @@
+// Copyright 2017 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"log"
+	"syscall"
+)
+
+// Uname returns the uname of the host machine.
+func Uname() string {
+	buf := syscall.Utsname{}
+	err := syscall.Uname(&buf)
+	if err != nil {
+		log.Fatal("Error!")
+	}
+	str := "(" + charsToString(buf.Sysname[:])
+	str += " " + charsToString(buf.Release[:])
+	str += " " + charsToString(buf.Version[:])
+	str += " " + charsToString(buf.Machine[:])
+	str += " " + charsToString(buf.Nodename[:])
+	str += " " + charsToString(buf.Domainname[:]) + ")"
+	return str
+}

cmd/prometheus/uname_linux_int8.go

@@ -0,0 +1,25 @@
+// Copyright 2017 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build 386 amd64 arm64 mips64 mips64le mips mipsle
+// +build linux
+
+package main
+
+func charsToString(ca []int8) string {
+	s := make([]byte, len(ca))
+	for i, c := range ca {
+		s[i] = byte(c)
+	}
+	return string(s[0:len(ca)])
+}

cmd/prometheus/uname_linux_uint8.go

@@ -0,0 +1,25 @@
+// Copyright 2017 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build arm ppc64 ppc64le s390x
+// +build linux
+
+package main
+
+func charsToString(ca []uint8) string {
+	s := make([]byte, len(ca))
+	for i, c := range ca {
+		s[i] = byte(c)
+	}
+	return string(s[0:len(ca)])
+}