From 90b12bd71bb9fc79a4640b9112c13ef529d0196a Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Fri, 5 Dec 2014 22:26:11 +0000 Subject: Initial commit --- doc/s6-notifywhenup.html | 80 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 doc/s6-notifywhenup.html (limited to 'doc/s6-notifywhenup.html') diff --git a/doc/s6-notifywhenup.html b/doc/s6-notifywhenup.html new file mode 100644 index 0000000..ad7ef8e --- /dev/null +++ b/doc/s6-notifywhenup.html @@ -0,0 +1,80 @@ + + + + + s6: the s6-notifywhenup program + + + + + + +

+s6
+Software
+skarnet.org +

+ +

The s6-notifywhenup program

+ +

+s6-notifywhenup launches a daemon while listening to a file descriptor, +and sends a 'U' event to a fifodir when it +receives something on that file descriptor. +

+ +

+This page explains why this program is +needed. +

+ +

Interface

+ +

+     s6-notifywhenup [ -d fd ] [ -e fifodir ] [ -f ] [ -t timeout ] prog...
+

+ +

s6-notifywhenup forks and executes prog... as the +parent, with a pipe from prog...'s stdout to the child.
The child waits for EOF on the pipe. When it gets it, if there +have been other characters written before the EOF, it sends a 'U' +event to the ./event fifodir.
The child exits 0.

+ +

Options

+ +

-d fd : listen to +prog's output on descriptor fd. The default is 1.
-e fifodir : send a 'U' event to fifodir +fifodir. Default is ./event.
-f : simple fork. Normally, s6-notifywhenup doubleforks, +in order to accommodate for a +prog that does not expect to have a child and avoid a +pending zombie. This option avoids the doublefork, but it should only be +set if prog reaps even children it doesn't know it has.
-t timeout : if no EOF has been received +after timeout milliseconds, exit without sending the event. +Default is 0, meaning infinite.

+ +

Notes

+ +

s6-notifywhenup executes prog... as the parent in order +for prog to keep the same pid, which is vital for supervised +processes.
s6-notifywhenup can be used, for instance, with +s6-tcpserver +and its -1 option, so that reliable startup notification is +achieved. s6-notifywhenup -f s6-tcpserver -1 args will +send a 'U' event to ./event when s6-tcpserver is actually +listening to its network socket.
The s6-svwait program can be used +to wait for 'U' events.

+ + + -- cgit v1.2.3