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c92af038fb
This is an example external logging service which can be enabled by
adding it to the `init` section of the .yml, for example:
...
init:
- linuxkit/init:35866bb276c264a5f664bfac7456f4b9eeb87a4d
- linuxkit/runc:v0.4
- linuxkit/containerd:f2bc1bda1ab18146967fa1a149800aaf14bee81b
- linuxkit/ca-certificates:v0.4
- linuxkit/memlogd:cc035e5c9e4011ec1ba97a181a6689fc90965ce9
onboot:
...
Signed-off-by: David Scott <dave.scott@docker.com>
98 lines
2.3 KiB
Go
98 lines
2.3 KiB
Go
package main
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import (
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"flag"
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"fmt"
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"io"
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"log"
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"net"
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"os"
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"os/exec"
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"syscall"
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)
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func getLogFileSocketPair() (*os.File, int) {
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fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0)
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if err != nil {
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panic(err)
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}
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localFd := fds[0]
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remoteFd := fds[1]
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localLogFile := os.NewFile(uintptr(localFd), "")
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return localLogFile, remoteFd
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}
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func sendFD(conn *net.UnixConn, remoteAddr *net.UnixAddr, source string, fd int) error {
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oobs := syscall.UnixRights(fd)
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_, _, err := conn.WriteMsgUnix([]byte(source), oobs, remoteAddr)
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return err
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}
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func main() {
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var err error
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var ok bool
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var serverSocket string
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var name string
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flag.StringVar(&serverSocket, "socket", "/var/run/linuxkit-external-logging.sock", "socket to pass fd's to memlogd")
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flag.StringVar(&name, "n", "", "name of sender, defaults to first argument if left blank")
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flag.Parse()
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args := flag.Args()
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if len(args) < 1 {
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log.Fatal("no command specified")
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}
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if name == "" {
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name = args[0]
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}
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localStdoutLog, remoteStdoutFd := getLogFileSocketPair()
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localStderrLog, remoteStderrFd := getLogFileSocketPair()
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var outSocket int
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if outSocket, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_DGRAM, 0); err != nil {
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log.Fatal("Unable to create socket: ", err)
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}
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var outFile net.Conn
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if outFile, err = net.FileConn(os.NewFile(uintptr(outSocket), "")); err != nil {
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log.Fatal(err)
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}
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var conn *net.UnixConn
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if conn, ok = outFile.(*net.UnixConn); !ok {
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log.Fatal("Internal error, invalid cast.")
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}
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raddr := net.UnixAddr{Name: serverSocket, Net: "unixgram"}
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if err = sendFD(conn, &raddr, name+".stdout", remoteStdoutFd); err != nil {
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log.Fatal("fd stdout send failed: ", err)
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}
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if err = sendFD(conn, &raddr, name+".stderr", remoteStderrFd); err != nil {
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log.Fatal("fd stderr send failed: ", err)
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}
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cmd := exec.Command(args[0], args[1:]...)
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outStderr := io.MultiWriter(localStderrLog, os.Stderr)
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outStdout := io.MultiWriter(localStdoutLog, os.Stdout)
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cmd.Stderr = outStderr
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cmd.Stdout = outStdout
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if err = cmd.Run(); err != nil {
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if exitError, ok := err.(*exec.ExitError); ok {
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// exit with exit code from process
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status := exitError.Sys().(syscall.WaitStatus)
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os.Exit(status.ExitStatus())
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} else {
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// no exit code, report error and exit 1
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fmt.Println(err)
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os.Exit(1)
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}
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}
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}
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