ref: e2e50a8e5a74452672f9418bcdfe4de10f600ed0
dir: /man/2/styxpersist/
.TH STYXPERSIST 2
.SH NAME
styxpersist \- persistent 9P (Styx) connection
.SH SYNOPSIS
.EX
include "sys.m";
include "styxpersist.m";
styxpersist := load Styxpersist Styxpersist->PATH;
init: fn(clientfd: ref Sys->FD, usefac: int, keyspec: string):
(chan of chan of ref Sys->FD, string);
.EE
.SH DESCRIPTION
.I Styxpersist
tries to maintain a persistent 9P (Styx) connection for its client.
.B Init
starts a process to serve 9P for the client on
.IR clientfd .
If
.I usefac
is non-zero,
.I styxpersist
will use
.IR factotum (2)
to do plan 9-style authentication if necessary,
and
.I keyspec
gives attribute-value pairs to pass to
.IR factotum 's
.B proxy
function.
.PP
.B Init
returns a tuple, say
.RI ( c ,\ err ).
If things have started successfully,
.I c
holds a channel that
.I styxpersist
uses to request a new connection to the server.
The caller of
.B init
should arrange that a process is ready to repeatedly receive on this channel,
dial the server, and send the resulting file descriptor (or
.B nil
if the connection was unsuccessful)
on the channel received,
.PP
If
.B init
failed,
.I c
will be
.B nil
and
.I err
describes the error.
.PP
If the server goes down, it redials as above, and tries to
re-open all the files that were open in the previous connection.
In the meantime all client access to the namespace is blocked.
.PP
Note that this service should only be used on conventional
file servers, where most reads and writes are idempotent.
.SH SOURCE
.B /appl/lib/styxpersist.b
.SH BUGS
Even on a conventional fileserver, some operations are non-idempotent;
namely create, rename, remove, and write to an append-only file.
If a fileserver dies while such a request is outstanding, it is unclear
what it should do. Currently it returns an error to the client if such a sitution occurs.
.PP
.I Styxpersist
is dependent on the capabilities of the local factotum to re-authenticate
Plan 9 style. If a client uses an external factotum with different keys,
.I styxpersist
may be unable to re-authenticate.
.SH "SEE ALSO"
.IR mount (1),
.IR dial (2)