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connect_envoy_pipe-bootstrap.go
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connect_envoy_pipe-bootstrap.go
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package pipebootstrap
import (
"bytes"
"flag"
"os"
"time"
"github.com/mitchellh/cli"
"github.com/hashicorp/consul/command/flags"
)
func New(ui cli.Ui) *cmd {
c := &cmd{UI: ui}
c.init()
return c
}
type cmd struct {
UI cli.Ui
flags *flag.FlagSet
help string
}
func (c *cmd) init() {
c.help = flags.Usage(help, c.flags)
}
func (c *cmd) Run(args []string) int {
// Read from STDIN, write to the named pipe provided in the only positional arg
if len(args) != 1 {
c.UI.Error("Expecting named pipe path as argument")
return 1
}
// This should never be alive for very long. In case bad things happen and
// Envoy never starts limit how long we live before just exiting so we can't
// accumulate tons of these zombie children.
time.AfterFunc(10*time.Second, func() {
// Force cleanup
os.RemoveAll(args[0])
os.Exit(99)
})
var buf bytes.Buffer
if _, err := buf.ReadFrom(os.Stdin); err != nil {
c.UI.Error(err.Error())
return 1
}
// WRONLY is very important here - the open() call will block until there is a
// reader (Envoy) if we open it with RDWR though that counts as an opener and
// we will just send the data to ourselves as the first opener and so only
// valid reader.
f, err := os.OpenFile(args[0], os.O_WRONLY|os.O_APPEND, 0700)
if err != nil {
c.UI.Error(err.Error())
return 1
}
if _, err := buf.WriteTo(f); err != nil {
c.UI.Error(err.Error())
return 1
}
if err = f.Close(); err != nil {
c.UI.Error(err.Error())
return 1
}
// Use Warn to send to stderr, because all logs should go to stderr.
c.UI.Warn("Bootstrap sent, unlinking named pipe")
// Removed named pipe now we sent it. Even if Envoy has not yet read it, we
// know it has opened it and has the file descriptor since our write above
// will block until there is a reader.
os.RemoveAll(args[0])
return 0
}
func (c *cmd) Synopsis() string {
return synopsis
}
func (c *cmd) Help() string {
return c.help
}
const synopsis = "Internal shim for delivering Envoy bootstrap without writing to file system"
const help = `
Usage: should only be used internally by consul connect envoy
`