STYXPERSIST(2) STYXPERSIST(2)
NAME
styxpersist - persistent 9P (Styx) connection
SYNOPSIS
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);
DESCRIPTION
Styxpersist tries to maintain a persistent 9P (Styx) connec-
tion for its client. Init starts a process to serve 9P for
the client on clientfd. If usefac is non-zero, styxpersist
will use factotum(2) to do plan 9-style authentication if
necessary, and keyspec gives attribute-value pairs to pass
to factotum's proxy function.
Init returns a tuple, say (c, err). If things have started
successfully, c holds a channel that styxpersist uses to
request a new connection to the server. The caller of init
should arrange that a process is ready to repeatedly receive
on this channel, dial the server, and send the resulting
file descriptor (or nil if the connection was unsuccessful)
on the channel received,
If init failed, c will be nil and err describes the error.
If the server goes down, it redials as above, and tries to
re-open all the files that were open in the previous connec-
tion. In the meantime all client access to the namespace is
blocked.
Note that this service should only be used on conventional
file servers, where most reads and writes are idempotent.
SOURCE
/appl/lib/styxpersist.b
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.
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, styxpersist may be
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STYXPERSIST(2) STYXPERSIST(2)
unable to re-authenticate.
SEE ALSO
mount(1), dial(2)
Page 2 Plan 9 (printed 11/22/24)