View Source slave (stdlib v6.0)
This module provides functions for starting Erlang slave nodes.
All slave nodes that are started by a master terminate automatically when the master terminates. All terminal output produced at the slave is sent back to the master node. File I/O is done through the master.
Slave nodes on other hosts than the current one are started with the ssh
program. The user must be allowed to ssh
to the remote hosts without being
prompted for a password. This can be arranged in a number of ways (for details,
see the ssh
documentation). A slave node started on the same host as the
master inherits certain environment values from the master, such as the current
directory and the environment variables. For what can be assumed about the
environment when a slave is started on another host, see the documentation for
the ssh
program.
An alternative to the ssh
program can be specified on the command line to
erl(1)
as follows:
-rsh Program
Note that the command specified with the -rsh
flag is treated as a file name
which may contain spaces. It is thus not possible to include any command line
options. The remote node will be launched as
"$RSH" "$REMOTE_HOSTNAME" erl -detached -noinput ...
, so the erl
command
must be found in the path on the remote host.
The slave node is to use the same file system at the master. At least, Erlang/OTP is to be installed in the same place on both computers and the same version of Erlang is to be used.
A node running on Windows can only start slave nodes on the host on which it is running.
The master node must be alive.
Summary
Functions
Calls pseudo(Master, ServerList)
. If you want to start a node
from the command line and set up a number of pseudo servers, an Erlang runtime
system can be started as follows
Starts a number of pseudo servers. A pseudo server is a server with a registered name that does nothing but pass on all message to the real server that executes at a master node. A pseudo server is an intermediary that only has the same registered name as the real server.
Runs a pseudo server. This function never returns any value and the process that
executes the function receives messages. All messages received are simply passed
on to Pid
.
Equivalent to start(Host, Name)
where Name
is the same
as the node that executes this call.
Equivalent to start(Host, Name, [])
Starts a slave node on host Host
. Host names need not necessarily be specified
as fully qualified names; short names can also be used. This is the same
condition that applies to names of distributed Erlang nodes.
Equivalent to start_link/3
Equivalent to start_link/3
Starts a slave node in the same way as start/1,2,3
, except that the slave node
is linked to the currently executing process. If that process terminates, the
slave node also terminates.
Stops (kills) a node.
Functions
Calls pseudo(Master, ServerList)
. If you want to start a node
from the command line and set up a number of pseudo servers, an Erlang runtime
system can be started as follows:
% erl -name abc -s slave pseudo klacke@super x --
Starts a number of pseudo servers. A pseudo server is a server with a registered name that does nothing but pass on all message to the real server that executes at a master node. A pseudo server is an intermediary that only has the same registered name as the real server.
For example, if you have started a slave node N
and want to execute pxw
graphics code on this node, you can start server pxw_server
as a pseudo server
at the slave node. This is illustrated as follows:
rpc:call(N, slave, pseudo, [node(), [pxw_server]]).
Runs a pseudo server. This function never returns any value and the process that
executes the function receives messages. All messages received are simply passed
on to Pid
.
-spec start(Host) -> {ok, Node} | {error, Reason} when Host :: inet:hostname(), Node :: node(), Reason :: timeout | no_rsh | {already_running, Node}.
Equivalent to start(Host, Name)
where Name
is the same
as the node that executes this call.
-spec start(Host, Name) -> {ok, Node} | {error, Reason} when Host :: inet:hostname(), Name :: atom() | string(), Node :: node(), Reason :: timeout | no_rsh | {already_running, Node}.
Equivalent to start(Host, Name, [])
-spec start(Host, Name, Args) -> {ok, Node} | {error, Reason} when Host :: inet:hostname(), Name :: atom() | string(), Args :: string(), Node :: node(), Reason :: timeout | no_rsh | {already_running, Node}.
Starts a slave node on host Host
. Host names need not necessarily be specified
as fully qualified names; short names can also be used. This is the same
condition that applies to names of distributed Erlang nodes.
The name of the started node becomes Name@Host
.
The slave node resets its io:user/0
process so that all terminal I/O that is
produced at the slave is automatically relayed to the master. Also, the file
server is relayed to the master.
Argument Args
is used to set erl
command-line arguments. It is
passed to the new node and can be used for a variety of purposes; see
erl(1)
.
As an example, suppose that you want to start a slave node at host H
with node
name Name@H
and want the slave node to have the following properties:
- Directory
Dir
is to be added to the code path. - The Mnesia directory is to be set to
M
. - The Unix
DISPLAY
environment variable is to be set to the display of the master node.
The following code is executed to achieve this:
E = " -env DISPLAY " ++ net_adm:localhost() ++ ":0 ",
Arg = "-mnesia_dir " ++ M ++ " -pa " ++ Dir ++ E,
slave:start(H, Name, Arg).
The function returns {ok, Node}
, where Node
is the name of the new node,
otherwise {error, Reason}
, where Reason
can be one of:
timeout
- The master node failed to get in contact with the slave node. This can occur in a number of circumstances:- Erlang/OTP is not installed on the remote host.
- The file system on the other host has a different structure to the the master.
- The Erlang nodes have different cookies.
no_rsh
- No remote shell program was found on the computer. Note thatssh
is used by default, but this can be overridden with the-rsh
flag.{already_running, Node}
- A node with nameName@Host
already exists.
-spec start_link(Host) -> {ok, Node} | {error, Reason} when Host :: inet:hostname(), Node :: node(), Reason :: timeout | no_rsh | {already_running, Node}.
Equivalent to start_link/3
-spec start_link(Host, Name) -> {ok, Node} | {error, Reason} when Host :: inet:hostname(), Name :: atom() | string(), Node :: node(), Reason :: timeout | no_rsh | {already_running, Node}.
Equivalent to start_link/3
-spec start_link(Host, Name, Args) -> {ok, Node} | {error, Reason} when Host :: inet:hostname(), Name :: atom() | string(), Args :: string(), Node :: node(), Reason :: timeout | no_rsh | {already_running, Node}.
Starts a slave node in the same way as start/1,2,3
, except that the slave node
is linked to the currently executing process. If that process terminates, the
slave node also terminates.
For a description of arguments and return values, see
start/1,2,3
.
-spec stop(Node) -> ok when Node :: node().
Stops (kills) a node.