README
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goagain
Zero-downtime restarts in Go
The goagain package provides primitives for bringing zero-downtime restarts to Go applications that accept connections from a net.TCPListener or net.UnixListener.
Have a look at the examples because it isn't just a matter of importing the library and everything working. Your main function will have to accomodate the goagain protocols and your process will have to have some definition (however contrived you like) of a graceful shutdown process.
Installation
go get github.com/rcrowley/goagain
Usage
Send SIGUSR2 to a process using goagain and it will restart without downtime.
example/single/main.go: The Single strategy (named because it calls execve(2) once) operates similarly to Nginx and Unicorn. The parent forks a child, the child execs, and then the child kills the parent. This is easy to understand but doesn't play nicely with Upstart and similar direct-supervision init(8) daemons. It should play nicely with systemd.
example/double/main.go: The Double strategy (named because it calls execve(2) twice) is experimental so proceed with caution. The parent forks a child, the child execs, the child signals the parent, the parent execs, and finally the parent kills the child. This is regrettably much more complicated but plays nicely with Upstart and similar direct-supervision init(8) daemons.
Documentation
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Overview ¶
Zero-downtime restarts in Go.
Index ¶
- Constants
- Variables
- func AwaitSignals(l net.Listener) (err error)
- func Dummy()
- func Exec(l net.Listener) error
- func ForkExec(l net.Listener) error
- func GetEnvs() (l net.Listener, ppid int, err error)
- func IsErrClosing(err error) bool
- func Kill() error
- func KillParent(ppid int) error
- func Listener(forkHook func()) (l net.Listener, err error)
- func Wait(l net.Listener) (syscall.Signal, error)
Constants ¶
const ( // The Single-exec strategy: parent forks child to exec with an inherited // net.Listener; child kills parent and becomes a child of init(8). Single strategy = iota // The Double-exec strategy: parent forks child to exec (first) with an // inherited net.Listener; child signals parent to exec (second); parent // kills child. Double )
const ( SIGINT = syscall.SIGINT SIGQUIT = syscall.SIGQUIT SIGTERM = syscall.SIGTERM SIGUSR2 = syscall.SIGUSR2 )
Don't make the caller import syscall.
Variables ¶
var ( // OnSIGHUP is the function called when the server receives a SIGHUP // signal. The normal use case for SIGHUP is to reload the // configuration. OnSIGHUP func(l net.Listener) error // OnSIGUSR1 is the function called when the server receives a // SIGUSR1 signal. The normal use case for SIGUSR1 is to repon the // log files. OnSIGUSR1 func(l net.Listener) error // The strategy to use; Single by default. Strategy strategy = Single )
var OnForkHook func()
Functions ¶
func AwaitSignals ¶
Block this goroutine awaiting signals. Signals are handled as they are by Nginx and Unicorn: <http://unicorn.bogomips.org/SIGNALS.html>.
func GetEnvs ¶
Convert and validate the GOAGAIN_FD, GOAGAIN_NAME, and GOAGAIN_PPID environment variables. If all three are present and in order, this is a child process that may pick up where the parent left off.
func IsErrClosing ¶
Test whether an error is equivalent to net.errClosing as returned by Accept during a graceful exit.
func Kill ¶
func Kill() error
Kill process specified in the environment with the signal specified in the environment; default to SIGQUIT.
func KillParent ¶
Send SIGQUIT to the given ppid in order to complete the handoff to the child process.
Types ¶
This section is empty.
Source Files
Directories