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) connection 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 connection. 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 unable to re-authenticate.

SEE ALSO

mount(1), dial(2)

STYXPERSIST(2 )

Rev:  Tue Mar 31 02:42:38 GMT 2015