NAME
lamshrink - Shrink a LAM universe.
SYNTAX
lamshrink [-dhv] [-w <delay>] <nodeid>
OPTIONS
-d Print detailed debugging information.
-h Print useful information on this command.
-v Be verbose.
<nodeid> Remove the LAM node with this ID.
-w <delay> Notify processes on the doomed node and pause for <delay>
seconds before proceeding.
DESCRIPTION
An existing LAM session, initiated by lamboot(1), can be shrunk to
include less nodes with lamshrink. One node is removed for each
invocation. At a minimum, the node ID is given on the command line.
Once lamshrink completes, the node ID is invalid across the remaining
nodes (as can be seen by running lamnodes(1)).
Existing application processes on the target node can be warned of
impending shutdown with the -w option. A LAM signal (SIGFUSE) will be
sent to these processes and lamshrink will then pause for the given
number of seconds before proceeding with removing the node. By
default, SIGFUSE is ignored. A different handler can be installed with
ksignal(2).
All application processes on all remaining nodes are always informed of
the death of a node. This is also done with a signal (SIGSHRINK),
which by default causes a process's runtime route cache to be flushed
(to remove any cached information on the dead node). If this signal is
re-vectored for the purpose of fault tolerance, the old handler should
be called at the beginning of the new handler. The signal does not, by
itself, give the process information on which node has been removed.
One technique for getting this information is to query the router for
information on all relevant nodes using getroute(2). The dead node
will cause this routine to return an error.
FAULT TOLERANCE
If enabled with lamboot(1), LAM will watch for nodes that fail. The
procedure for removing a node that has failed is the same as lamshrink
after the warning step. In particular, the SIGSHRINK signal is
delivered.
EXAMPLES
lamshrink -v n1 Remove LAM on n1. Report about important steps as
they are done.
lamshrink n30 -w 10
Inform all processes on LAM node 30, that the node will be dead in
10 seconds. Wait 10 seconds and remove the node. Operate
silently.
SEE ALSO
lamboot(1), lamnodes(1), ksignal(2), getroute(2)