Add statsclient - pure Go implementation for stats API

Change-Id: Ia5bab652c6089378697459f477f9060dc7a53e90
Signed-off-by: Ondrej Fabry <ofabry@cisco.com>

3 files changed, 147 insertions, 0 deletions

diff --git a/vendor/github.com/ftrvxmtrx/fd/LICENSE.MIT b/vendor/github.com/ftrvxmtrx/fd/LICENSE.MIT
new file mode 100644
index 0000000..136e69e
--- /dev/null
+++ b/vendor/github.com/ftrvxmtrx/fd/LICENSE.MIT
@@ -0,0 +1,18 @@
+Copyright © 2012 Serge Zirukin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/vendor/github.com/ftrvxmtrx/fd/README.md b/vendor/github.com/ftrvxmtrx/fd/README.md
new file mode 100644
index 0000000..7a8a239
--- /dev/null
+++ b/vendor/github.com/ftrvxmtrx/fd/README.md
@@ -0,0 +1,25 @@
+# fd
+
+Package fd provides a simple API to pass file descriptors
+between different OS processes.
+
+It can be useful if you want to inherit network connections
+from another process without closing them.
+
+Example scenario:
+
+ * Running server receives a "let's upgrade" message
+ * Server opens a Unix domain socket for the "upgrade"
+ * Server starts a new copy of itself and passes Unix domain
+   socket name
+ * New copy starts reading data from the socket
+ * Server sends its state over the socket, also sending the number
+   of network connections to inherit, then it sends those connections
+   using fd.Put()
+ * New server copy reads the state and inherits connections using fd.Get(),
+   checks that everything is OK and writes an "OK" message to the socket
+ * Server receives "OK" message and kills itself
+
+## Documentation
+
+[fd on godoc.org](http://godoc.org/github.com/ftrvxmtrx/fd)
diff --git a/vendor/github.com/ftrvxmtrx/fd/fd.go b/vendor/github.com/ftrvxmtrx/fd/fd.go
new file mode 100644
index 0000000..a5a4d48
--- /dev/null
+++ b/vendor/github.com/ftrvxmtrx/fd/fd.go
@@ -0,0 +1,104 @@
+// Package fd provides a simple API to pass file descriptors
+// between different OS processes.
+//
+// It can be useful if you want to inherit network connections
+// from another process without closing them.
+//
+// Example scenario:
+//
+//   1) Running server receives a "let's upgrade" message
+//   2) Server opens a Unix domain socket for the "upgrade"
+//   3) Server starts a new copy of itself and passes Unix domain socket name
+//   4) New copy starts reading for the socket
+//   5) Server sends its state over the socket, also sending the number
+//      of network connections to inherit, then it sends those connections
+//      using fd.Put()
+//   6) New copy reads the state and inherits connections using fd.Get(),
+//      checks that everything is OK and sends the "OK" message to the socket
+//   7) Server receives "OK" message and kills itself
+package fd
+
+import (
+	"net"
+	"os"
+	"syscall"
+)
+
+// Get receives file descriptors from a Unix domain socket.
+//
+// Num specifies the expected number of file descriptors in one message.
+// Internal files' names to be assigned are specified via optional filenames
+// argument.
+//
+// You need to close all files in the returned slice. The slice can be
+// non-empty even if this function returns an error.
+//
+// Use net.FileConn() if you're receiving a network connection.
+func Get(via *net.UnixConn, num int, filenames []string) ([]*os.File, error) {
+	if num < 1 {
+		return nil, nil
+	}
+
+	// get the underlying socket
+	viaf, err := via.File()
+	if err != nil {
+		return nil, err
+	}
+	socket := int(viaf.Fd())
+	defer viaf.Close()
+
+	// recvmsg
+	buf := make([]byte, syscall.CmsgSpace(num*4))
+	_, _, _, _, err = syscall.Recvmsg(socket, nil, buf, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	// parse control msgs
+	var msgs []syscall.SocketControlMessage
+	msgs, err = syscall.ParseSocketControlMessage(buf)
+
+	// convert fds to files
+	res := make([]*os.File, 0, len(msgs))
+	for i := 0; i < len(msgs) && err == nil; i++ {
+		var fds []int
+		fds, err = syscall.ParseUnixRights(&msgs[i])
+
+		for fi, fd := range fds {
+			var filename string
+			if fi < len(filenames) {
+				filename = filenames[fi]
+			}
+
+			res = append(res, os.NewFile(uintptr(fd), filename))
+		}
+	}
+
+	return res, err
+}
+
+// Put sends file descriptors to Unix domain socket.
+//
+// Please note that the number of descriptors in one message is limited
+// and is rather small.
+// Use conn.File() to get a file if you want to put a network connection.
+func Put(via *net.UnixConn, files ...*os.File) error {
+	if len(files) == 0 {
+		return nil
+	}
+
+	viaf, err := via.File()
+	if err != nil {
+		return err
+	}
+	socket := int(viaf.Fd())
+	defer viaf.Close()
+
+	fds := make([]int, len(files))
+	for i := range files {
+		fds[i] = int(files[i].Fd())
+	}
+
+	rights := syscall.UnixRights(fds...)
+	return syscall.Sendmsg(socket, nil, rights, nil, 0)
+}